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'."^THE JOURNAL @NJ THE «

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Established in 1 962

Edited by WILLIAM HOVANITZ

Volume 1

1962 - 1963

f

Published at

1140 W. Orange Grove Ave., Arcadia, California, U.S.A.

THE JOURNAL OF RESEARCH

ON THE LEPIDOPTERA

is sponsored by

THE LEPIDOPTERA FOUNDATION

CONTENTS

Volume 1	Number 1	August, 1962
Editorial		1

Variation in the silvering of Argynnis (Speyena) cdlippe in the interior mountain area of south central California . . .

Oscar Elton Sette 3

The effect of various food plants on survival and growth rate of Pieris .... William Hovanitz and Vincent C. S. Chang 21

General characteristics of the movements of Vanessa cardui (L.)

J. W. Tffden 43

Three factors affecting larval choice of food plant

William Hovanitz and Vincent C. S. Chang 51

The generic, specific and lower category names of the Nearctic butterflies. Part 1 •— The genus Pieris . . Paddy McHenry 63

The distribution of the species of the genus Pieris in North America William Hovanitz 73

Did the caterpillar exterminate the giant reptile? ....

S. E. Flanders 85

Further evidence of the distribution of some boreal Lepidoptera in the Sierra Nevada Clyde Eriksen 89

Argynnis and Speyer ia . William Hovanitz 94

Volume 1 Number 2 January, 1963

Composition and relative abundance in a temperate zone butterfly fauna . . . Thomas C. Emmel and John F. Emmel 97

The Argynnis populations of the Sand Creek area, Klamath Co., Oregon, Part I .... J. W. Tilden 109

Caterpillar Versus Dinosaur? . . . Theodore H. Eaton, Jr. 114

Geographical distribution and variation of the Genus Argynnis I. Introduction

II. Argynnis idalia William Hovanitz 117

The relation of Pieris virginiensis Edw. to Pieris napi L.

Species formation in Pieris? ..... Wiliam Hovanitz 124

The male genitalia of some Co lias species . Bjorn Petersen 135

The effect of hybridization of host-plant strains on growth rate

and mortality of Pieris rapae .

WiUiam Hovanitz and Vincent C. S. Chang 157

Notice-editorial

162

Change of food plant preference by larvae of Pieris rapae

controlled by strain selection, and the inheritance of this trait

William Hovanitz and Vincent C. S. Chang 163

Volume 1 Number 3 March, 1963

Selection of allyl isothiocyanate by larvae of Pieris rapae and

the inheritance of this trait

William Hovanitz and Vincent C. S. Chang 169

Biology of the Ceanothus stem-gall moth, Periploca ceanothiella

(Cosens), with consideration of its control. J. Alex Munro 183

Larval food-plant records for six western Papilios, ....

John F. Emmel and ThtMnas C. Emmel 191

CoUas philodice in Chiapa^ Mexico . . Thomas C. Emmel 194

Notes on the early stages of two California geometrids

John Adams Comstock 195

Geographical distribution and variation of the genus Argynnis

III. Argynnis diana William Hovanitz 201

The generic, specific and lower category names of the nearctic

butterflies. Part 2 — The Genus Colias . Paddy McHenry 209

A standard method for mounting whole adult lepidoptera on

slides utilizing polystyrene plastic . . Charles L. Hogue 223

Volume 1 Number A May, 1963

Techniques in the study of population structure in Philotes sonorensis

Rudolf H. T. Mattoni and Marvin S. B. Seiger 237 Early stages of a southern California Geometrid moth,

Drepanulafrix hulsti hulsti (Dyar) John Adams Comstock 245

The effeaiveness of different isothiocyanates on attraaing larvae of Pieris rapae

William Hovanitz, Vincent C. S. Chang and Gerald Honch 249

The origin of a sympatric species in Colias through the aid of

natural hybridization William Hovanitz 261

A method for breeding Pieris napi and Pieris bryoniae

Bjorn Petersen 275

An analysis of the North American species of the genus

Callophrys J. w. Tilden 281

THE LEPIDOPTERA FOUNDATION 301

Notice 302


Volume 1	Number 1	August, 1962

Established in 1 962 Published at

1140 W. Orange Grove Ave., Arcadia, California, U.S.A.

Edited by WILLIAM HOVANITZ

WITH EMPHASIS ON ENVIRONMENTALLY AND GENE- TICALLY INDUCED VARIATION, population analysis, evolution, phylogenetic taxonomy, zoogeography, comparative morphology, ecol- ogy, geographical variation, speciation, physiology, etc. In short, quality tuork on any aspect of research on the Lepidoptera.

THE PURPOSE OE THE JOURNAL is to combine in one source the work in this field for the aid of students of this group of insects in a way not at present available. The JOURNAL will attempt to publish primarily only critical and complete papers of an analytical nature, though there will be a limited section devoted to shorter papers and notes.

RATES: $ 8.00 per volume, personal subscription.

$12.00 per volume, institutional subscription.

Benefactor subscriptions are encouraged. These may be any amount over those above.

All amounts are in U.S. dollars, payable in the U.S.A.

AUTHORS ARE REQUESTED to refer to the Journal as an example of the form to be used in preparing their manuscripts. Fifty separates will be supplied to authors free; reprints will be sold at printer’s rates if ordered at time galley proofs are returned. If proofs are not returned promptly, the editor reserves the right to withhold publication, or to proceed with no responsibility. All issues of the Journal will be copyrighted; in submitting a paper each author agrees that the material has not been published elsewhere.

MANUSCRIPTS AND SUBSCRIPTIONS should be mailed to the address noted above.

BENEFACTORS Individuals or institutions who by reason of their interest in the welfare or research on the Lepidoptera, and in its publication, who wish to contribute beyond the cost of a subscription, will be listed here.

BIO-METAL ASSOCIATES THOMAS C. EMMEL ANONYMOUS DONOR ANONYMOUS DONOR

1(1):1,1962

Journal of Research on the Lepidoptera

EDITORIAL

Starting a new journal is not an easy matter, nor is it a matter free of controversy. This is especially the case where a new journal, as this one, is started without the support of an existing society. This journal is intended as a meeting ground for papers on all aspects of the biology of the Lepidoptera, moths and butterflies alike. Too many entomolog- ical journals don’t offer publication of articles of the length necessary to present sound data and Completeness of effort. The Lepidoptera are a group of insects second to none in the scope of our knowledge about them: work in this fieM has reached the higher levels of learning and a journal is required to keep pace with this knowledge at the same level.

A journal with a wide scope is our aim — narrow in the taxonomic sense but wide in the biological sense. The journal will attempt to publish primarily only critical and complete papers of an analytical na- ture, though there will be a limited section devoted to shorter papers and notes. There will be emphasis on environmentally and genetically induced variation, population analysis, evolution, phylogenetic taxon- omy, zoo-geography, comparative morphology, ecology, geographical variation, speciation, physiology, etc.

It has been very gratifying to receive so many subscriptions on the basis of merely a brochure; every effort will be made to keep the journal up to the standard expected of us. The response in so short a time has served to show those who have generously provided the finances that a journal of this type has been needed and will fill a desirable niche.

We are happy to publish in this first issue a number of papers which the authors were able to get ready on "short notice". There is a preponderance on one taxonomic group, but with different points in mind. With this first issue out, we offer the pages of this journal to all with papers to publish on the Lepidoptera that fit the intent of the journal. A wider range of papers will come in future issues.

1

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l(l):3-20, 1962

Journal of Research on the Lepidoptera

VARIATION IN THE SILVERING OF ARGYNNIS (SPEYERIA) CALLIPPE IN THE INTERIOR MOUNTAIN AREA OF SOUTH CENTRAL CALIFORNIA

OSCAR ELTON SETTE

23643 Arbor Avenue, Los Altos, California

In a comprehensive study of the geographic variation of Argynnis (Speyeria) callippe Boisduval, based on examination of about 2750 specimens from many localities well distributed through out the range of the species in California, Hovanitz (1943) recog- nized several main divisions of this species complex. Among them are the *'South Coast Range Population” extending from the San Fran- cisco Bay area southward through the Coast Ranges into Lower Calif- ornia and the "Western Sierra Nevada Populations” extending in a band along the western Sierra Nevada, at moderate elevations from the region west of Lassen Peak southward to about the Greenhorn Mountains at the southern end of the Sierra Nevada. He found that these two population groups are connected through a "Southern Zone of Intergradation” by a "series of steps across the Piute Mountains, the Tehachapi Mountains and the Sierra Madre Range.”’

He characterizes the populations in the Southern Zone of Inter- gradation as follows:

"From the Santa Monica Mountains ‘ on the coast, where the typical callippe of this (the South Coast Range) region lives, it is found that in going inland (Charlton Flat, Mint Canyon and ’Ridge Route’) the lightness of all colors increases. The butterfly becomes smaller and the light colored band and spots on the upper surface of the wings tend to become obliterated, leaving a more uniformly colored wing surface such as is present in the western Sierra Nevada gradient. However, the yellow- brown color is very much lighter than in the latter and the band on the under side of the hind wings is still yellow; the spots are still always fully silvered. The tendency toward these conditions is the more marked the farther from the coast and the farther into the Tehachapi Range the populations exist. In the Tehachapi Range, the butterflies are very lightly colored and the band on the upper surface of the wings is rare; the spots are still silvered. At Havilah, Piute Mountains, the population consists of some silvered, some unsilvered and some intermediate spotted

IThis range is not named on many maps. It lies parallel to, and south of, the middle portion of the Cuyama River which is the long north branch of the shorter Santa Mafia River shown discharging into the ocean at about lat 35° in Fig. 1.

3

4

SETTE

J. Res. Lepid,

individuals (this is the type locality of macaria Edws.); the exact fre- quency of these types is not known; but there is a high percentage of silvered and unsilvered present ... In the Greenhorn Mountains, the segregation into a silvered population on the eastern side of the summit and an unsilvered one on the western side is decidedly apparent, though mixing occurs toward the south, where the populations unite”.

The main purpose of this paper is to describe semi-quantitatively the variation of silvering within the Southern Zone of Intergradation. The silvery decoration of animals is far less common than the pigmen- tal coloration. While Hovanitz ( 1941 ) has found general qualitative correlations of the pigmental coloration of ^butterflies with environ- mental conditions, he finds the significance of silvering in callippe "quite incomprehensible" (Hovanitz, 1943, p. 420). Some peculiari- ties of the silvering data revealed by the semi -quantitative treatment in this paper suggests that studies of its physico-chemical nature and genetic control might be rewarding. An hypothesis is advanced as a point of departure for such studies.

THE SAMPLES

The material for this study consists of complete series of callippe that I collected during June 8 to 15, 1957 in company with Fred T. Thorne, and one sample from Bouquet Canyon consisting of part of a series taken in 1952 by Thorne and kindly given to me. In brok- ing the series Thorne exercised no conscious selection for color or pattern, though worn and damaged specimens were discarded.

Parallel or convergent evolution among the Argynnids in some regions presents problems of species identification. In the Southern Zone of Intergradation this problem arises between calliiype and cor- onis Behr. The latter, as the subspecies hennei Gunder, flies with cal- lippe and resembles it so closely that confident identification requires either great familiarity with both species or known series from the region for comparison. L. P. Grey is in possession of both and kindly reviewed my field identifications. These had been made in consulta- tion with Thorne. At the time neither of us had previous acquain- tance with hennei, though we were both familiar with several other subspecies of coronis. Two specimens I had labelled callippe proved to be undoubted coronis. One labelled callippe came back from Grey with the notation, "Could this be coronis? (Don’t ask me!." Another labelled coronis bore Grey’s notation "I think it is a callippe!* The last two, when spread and compared with the now-available good series of hennei, appear to me to be undoubted coronis, though the under side wing surface (the only surface exposed to Grey’s examina- tion) is remarkably like the callippe from the same locality. These four speciments have been excluded from the samples.

In the list that follows, the collections are grouped by localities. Each group contains mainly specimens taken at one location, to which have been added a few specimens from nearby locations. Those

i(j):}-20, 1^62

VARIATION IN SILVERING

5

in the main group, I believe, are members of a single interbreeding colony; the others may consist of strays from the same colony in some instances, and in others, may be strays from some other colony. All localities are in Kern County except Sandberg’s and Bouquet Canyon which are in Los Angeles County. Distances from named places are given to the nearest mile (I.6I km) measured on a straight line on large-scale road maps. Directions, also determined from such maps, are referenced to true North and stared in Mariners’ abbreviations appropriate to the 32 -point compass. Thus southwest is siven as SW, southwest by west as SWxW and west southwest as WSW. These are 11.25° steps and allowing for measuring inaccuracy are correct to about the nearest 15°. Elevations were taken by aneroid altimeter graduated in 100-foot (30.5 m) units and probably accurate to ± 200 feet. Botanical names are according to Jepson (1923 - 1925), Abrams (1940, 1944 and 1951) and Abrams and Ferris (I960). No- menclature of the butterflies follows the list by McDunnough (1938) except for the genus {Speyeria), which, at the species and subspecies level follows the arrangement of Dos Passos and Grey (1947).

A. East slope, Greenhorn Mountains. June 12, 1957, 18 males and 1 female taken 6 miles WSW of Kernville, elevation 4900 ft., along the road leading steeply from Isabella Reservoir to Greenhorn Mountain Park passing between Tittle and Rattlesnake Creeks, in association of Digger Pine (Pinus sabiniana Dough), Oak (Quercus sp), California Fremontia (Premontia cali- fornica Torr.), and chaparral broken by grassy areas, with Yerba Santa {Brio- dictyon so.) flowers as nectar attractant; included in addition is 1 male taken 8 miles WxS of Kernville, elevation 5500 ft., Transition Zone, in a small roadside opening in Yellow Pine (Pinus ponder osa Dough) and Incense Cedar {Libocedrus decurrens Torr.) forest.

B. West slope, Greenhorn Mountains. June 12, 1957, 58 males and 6 females taken 27 miles NE of Bakersfield, elevation 3300 ft., near the foot of Eugene Grade, in Digger Pine, Blue Oak (Qurcus douglasii Hook & Arn.) and grass association, with violets (Viola sp.) abundant; included in addition are 3 males and 1 female taken 26 miles NNE of Bakersfield, elevation 3000 ft., in Blue Oak and grass association, with riparian flora along a small creek.

C. Havilah. June 11, 1957, 13 males and 1 female taken 2 miles S of Havilah, elevation 3100 ft., Digger Pine, mixed oak and chaparral association with riparian flora along a small creek, mostly attracted to Yerb Santa flowers; in addition are 1 male from 1 mile north of Havilah, elevation 2800 ft., and another from 5 miles S of Havilah, elevation 3900 ft.

D. Walker Basin. June 11, 1957, 30 males and 6 females taken 10 miles SxW of Havilah, at the south end of Walker Basin, elevation 3200 ft.. Blue Ok and Grass association with sagebrush and violets. Hoarhound (Marrubium vulgare L.) attracted a few individuals, but most were taken in the characteristic slow, fluttering flight displayed when on breeding grounds.

E. Tehachapi. June 14, 1957, 12 males and 7 females taken 8 miles W of Tehachapi (the town), elevation 4700 ft, at the eastern end of Bear Valley in Blue Oak and grass association, with patches of sagebrush (Artemisia tri- dentata Nutt.), mostly acctracted to Wallflower (Erysimum sp.) flowers; in addition are 3 males from 7 miles W of Tehachapi, elevation 4600 ft., and 1 female from 3 miles SW of Tehachapi, elevation 4600 ft.

6

SETTE

/. Res. tepid.

I2 0‘

119*

118®

36'

35*

3 4*

FIGURE 1. Location of populations sampled (letters "A to H”) super- imposed on the distribution of Argynnis (Speyeria) callippe (shaded area) adapted from a portion of Hovanitz’ map (1943, Fig. 1) showing the distribu- tion of the "silvered spots” character by shading lines slanted upward to the left and the "unsilvered spots” character by shading lines slanted upward to the right. The Kern River (upper right) separates the Greenhorn Mountains to the north from the Piute Mountains to the south as it flows to a sink in the lower San Joaquin Valley (blank area at upper middle). At middle left is the Santa Maria River with the Cuyama River as its long north fork. At the lower right is the Santa Clara River. The crests of the higher mountains and ridges of the transverse series of ranges lie north of the Santa Clara River Drainage and south of the Cuyama River.

F. Lebec, June 8, 1957, 24 males and 8 females; June 9, 1957, 26 males and 4 females; and June 15, 1957, 11 males and 15 males; total, 61 males and 27 females taken 1 mile S of Lebec, elevation 3600 ft., in oak and grass association with adjacent chaparral including sagebrush {A. tridentata) , Buck- wheat Brush {Eriogonum^ fasciculatum Benth.) and Yerba Santa; some were at flowers of the last, others in breeding-ground flight.

(r;.-j-20, 1^62

VARIATION IN SILVERING

7

G. Sandberg^S (on old Ridge Route). June 9, 1957, 12 males and 3 females; June 15, 1957, 1 male and 2 females; total, 13 males and 5 females taken 9 miles ESE of Gorman in Digger Pine and sagebrush (not A. tridentata) associa- tion, with violets. Breeding ground behavior was predominant.

H. Bouquet Canyon. June 11 and 12, 1951, 18 males collected by Fred T. Thorne at "upper Bouquet Canyon, 4 miles down from Pine Creek — Lake Hughes road” (estimated 16 miles W of Palmdale, estimated elevation 3400 ft.).

HABITAT AND MESOSCALE DISTRIBUTION

According to these records callippe in this region occupies ele- vations from 2800_ to 5500 feet, but occurs in good concentrations only between 3100 and 4900 feet, generally, the upper portion of the Up- per Sonoran Life Zone. Its habitat is marked characteristically by scat- tered Blue Oak, Digger Pine, and sparse chaparral with sagebrush {A. tridentata) often pesent. Usually there are broad areas or small patches of grass present. Practically all of the localities are in grazing land, but at the time of our trip it was being very lightly grazed.

Violets were noted at only three of the locations. Where they were seen, the plants were abundant, mature, with fully-developed seed cap- sules and appeared about to dry up. Where violets were not seen, either they had dried up already, or the collecting was of members of the colony that had been drawn by nectar sources somewhat away from the site of the larval food plant.

During the trip we collected at 31 locations within the geographic range and elevation limits of this butterfly. Of these, seven obviously were in, or close to, callip'be colonies; five locations yielding only one or several specimens, evidently were not as close; and the remaining 19 locations where we took none probably were distant from colonies, though this may not have been true for a few places where we sighted an Argynnid or two v/hich could have been either this species or coro- nis. These indications favor a population model consisting of well- separated, compact colonies from which individuals do not stray often or far. This pattern is more accentuated in this region than in most others within my collecting experience.

Butterflies of 30 other species were taken at one or another of the seven locations where callippe were caught in good numbers. Plebeius acmon West, and Hew. and Hesperia lindseyi Holland were the most ubiquitous, occuring at most locations from the Greenhorn Mountains to Sandbergs. The former were taken in small numbers while the latr ter, in some locations were very abundant. In addition to these, the most common and prevalent in the Greenhorns and the Piutes were Euphydryas chalcedona Doubleday and Hewitt, Melitaea palla Boisdu- val, and Strymon saepl^m^ Boisduval; while through the Tehachapi to Sandberg’s they were Minois silvestris Edwards and Argynnis coronis Behr. If one of the specimens whose identification was questioned by

8

SETTE

/. Res. Lepid.

Grey is, as I believe, coronis, this species extended north at least to Havilah. Inasmuch as all coronis taken on this trip were fresh males, and in other regions within my collecting experience coronis flies some- what later than callippe, it is likely that a week or two later in the season coronis would have been found to be even more consistently a companion of callippe.

RELATIVE ABUNDANCE

The relative abundance in butterfly populations may be signifi- cant in studies of variation. From records extending through many years, Ford (1945) found that a rapid increase in abundance of the colonial butterflv Euphydryas aurina Rott was accompanied by "an ex- traordinary outburst of variation". When the increase ceased, the colony settled down to a comparatively uniform type, different from the one prevailing prior to the increase. Scientists differ as to the in- terpretation and significance of this phenomenon as a mechanism in evolution. Whatever the interpretation, if the generality of this phen- omenon is to be ascertained, records must be accumulated through the years for a number of butterfly populations.

To this end, there are placed on record in Table 1, estimates of relative abundance of callippe in each of the seven colonies sampled in 1957. This estimate is in terms of catching rate and assumes that the number caught in unit time is proportional to the abundance of the population in the area of collecting. It is homologous in concept to the measure "catch per unit of effort” almost universally and suc- cessfully (sometimes "calibrated” to a absolute abundance by tag-and- recapture experiments) used as a basic statistic in studying the dy- namics of fish population fluctuations (Ricker 1940). For callippe I have computed the catching rate, R, according to the formula:

R ^ Nc .

H - k Nt

where Nc is the number of callippe caught, H is the time, in hours, in the collecting period, Nt is the total number of specimens of all species caught (including callippe) during the collecting period, and k is a constant whose value depends on the methods and dexterity of the collector in caring for a specimen once it is in the net. By timing myself in the_caring, individually, for each of 150 specimens of a number of species from all families except Megathymidae under typ- ical field conditions, I found my k value to be 0.0155 hours (37.8 seconds ) .

In repeated samplings of several species I have fo*und R to be sur- prisingly stable. For callippe, the three samplings at Lebec are an ex- ample of this. Although stable, R as computed by this formula should

i(i):3’2o, I $62

VARIATION IN SILVERING

9

be regarded only as a first-order approximation, or index, of true rel- ative abundance, because it is affected by systematic error and several sources of variability, not all of them random. A more sophisticated iterative treatment theoretically should improve R, but it involves as- sumptions of uncertain merit awaiting test.

TABLE 1. Relative abundance in terms of catching rate, R, in number per males and by the per cent of the males that were fresh.

Catch- ing Per Per cent

Locality, date (1957) and elevation rate cent of males

(R) males fresh

A. E. slope, Greenhorns, el. 4900 ft., June 12 ....... * 39 84 86

B. W. slope, Greenhorns, el. 330 ft., June 12 ........ **227 91 52

C. Havilah, el. 3100ft., June 11 16 93 15

D. Walker Basin, el. 3200 ft., June 11 * 44 83 87

E. Tehachapi, el. 4600 - 4700 ft., June 14 33 67 79

F. Lebec, el. 3600 ft., June 8 24 75 84

F. Lebec, el. 3600 ft., June 9 24 87 69

F. Lebec, el. 3600 ft., June 15 30 42 45

G. Sandberg’s, el, 4000 ft., June 9 17 80 75

In the meantime, of most concern is that R increasingly underes- timates abundance as the latter increases, presenting simultaneous catching opportunities more often and usually avail can be taken of only one of them at a time. Recognizing this, the values in Table 1 that probably were moderately underestimated owing to this factor are marked with an asterisk, and the one value that was grossly under- estimated is marked with a double asterisk. At the other end of the scale, when only one or two specimens are caught during a collecting period, R has large error owing to random variability of incidences of encounters. Avoiding this. Table 1 gives catching rates computed for only the first-listed location under each locality, except for Tehach- api where the times and catches of the first two locations were pooled for computing the catching rate.

Another error source is that as kNt approaches H, a small error in k produces a large error in R. This approach was not close enough to be critical for the values given in Table 1, though the value for the west slope of the Greenhorn Mountains may have been moderately affected.

Every collector can think of a number of other obvious sources of error or variability such as weather conditions, unusual concentrations at attractants, etc.. These obvious ones can be avoided by comparing only sets of samplings taken under reasonably similar conditions, as is true for the set in Table 1 except as later noted.

Of course the catching rate reflects the relative abundance only at the stage of flight at which the collecting was done, and may yield values departing substantially from the inherent abundance. An esti-

10

SETTE

/. Re$. tepid.

mate of the stage of the flight is afforded by the relative numbers of fresh and worn individuals. In Table 1, recorded as *'fresh” were in- dividuals without readily perceptible random loss of scales or fringe. Damage reasonably attributable to accidental causes, such as notches, tears, breaks and rubbed streaks or patches was not considered. The data are given for males only, there not being enough females to yield reliable percentages. The two sexes were not combined for this sta- tistic because this would introduce extraneous variability owing to the tendency of females to emerge later than males. As evidence of this, only four of the 53 females listed in Table 2 were worn. More direct evidence is afforded by the Lebec samples. Those of June 8 and 9 were mostly males and mostly fresh. About a week later more than half of the males were worn and the females, all fresh, outnumbered the males. The sample from Havilah is anomalous in respect of percentage worn in relation to sex ratio. Although most of the males were worn, only one female was taken. Probably the greater ease of collecting males at the Yerba Santa flowers diverted us from the females which probably were widely scattered for ovipositing in the adjacent area which ap- peared to be the likely habitat for violets, though the plants were not observed, doubtless having dried up before our visit. At Sandberg’s the catching rate was substantially depressed bv a strong breeze sweep- ing the exposed slope and wafting many a disturbed butterfly out of stalking or pursuit range.

Appraising the catching rates in the light of these qualifying fac- tors, the presence of some worn males at all localities indicates that the callippe flight was well developed throughout the region. But the high percentage of fresh males and the scarcity of females suggests that the flight had not yet reached its peak at most localities except Lebec where it probably was near peak stage on June 15 and Havilah, where the male flight had apparently passed its peak. Allowing for the differ- ences in stage of flight and the collecting difficulties at Sandberg’s, it appears that relative abundance was capable of attaining a height-of- flight index of 30 to 40, probably closer to the latter, at all localities except the location on the west slope of the Greenhorn Mountains where abundance was at least an order of magnitude higher, and at Walker Basin where it probably was substantially higher than 40 per hour, though well below that on the west slope of the Greenhorn Moun- tains. Although we did not trace out the geographic extent of a colony in any of the localities, the impression gained while collecting, was that these two colonies covered more extensive areas than the rest. It may be concluded, first, that the samples were drawn from near the middle of the flight period and hence probably represent nearlv the modal characteristics of the population in each colony; and second, the colonies varied quite widely in population size, perhaps through more than one order of magnitude. Further results may emerge if compar- isons with changed levels of abundance become possible in the future.

1^62

VARIATION IN SILVERING

11

VARIATION IN SILVER SCALING

The silver scaling in callippe^ as in Argynnids generally, is confiined to certain pattern elements on the ventral wing surface. For the most part these are well defined spots in the apical and subapical area of the fore wing and all well defined spots in all areas of the hind wing. In addition, on heavily silvered individuals, silver scales may form ill defined streaks along the inner margin and in some of the interspaces between spots in the basal and discal areas of the hind wing. The pres- ent study is confined to the well defined spots of the hind wing. When unsilvered these spots are a light buff color, usually sharply bordered or outlined by brown scales. Some or all of the spots may be partly sil- vered. Then the silver scales and buff scales stand out in sharp con- trast to each other when specimens are held in the best relation to the light source and the eye to bring out the specular quality of the silver scales.

A fully quantitative measure of the degree of silvering would be the ratio of silvered scales to all scales in the area potentially subject to silvering. To avoid spending a prohibitive amount of time count- ing scales, I have employed a subjective system of scoring based on general appearance. It would have been desirable, too, to utilize ex- clusively the pristine fresh individuals, but to avoid reducing the num- ber below levels needed for tests of significance, I have scored the slightly and moderately worn individuals along with the fresh ones, ex- cluding only those whose loss of scales caused serious doubt as to their correct score. The penultimate column of Table 2 shows the number excluded for this reason.

Because the amount' of silvering sometimes differed appreciably in the basal and discal area, which will be called "disc” for brevity, from that in the submarginal area, called "margin”, the two portions of the wing were scored separately. Four grades of silvering were recognized: Grade 0 for complete lack of silver scales: Grade 1, when there were only flecks of silver well separated by buff scales; Grade 2, when some of the spots were unsilvered, others were partly silvered and still others were fully silvered, or any combination of two of these conditions; and Grade 3, when all spots were so fully silvered that there were no readily perceptible buff scales. The Disc Grade and the Margin Grade were treated as half scores and added together to arrive at the individual Score. Thus there are seven possible scores: 0 to 6, inclusive.

Of the 238 individuals scored, 50 had half scores that differed from each other by one grade point. None differed by more than one. Of the 50 with different half scores, the Disc Grade was higher than the Margin Grade for 40 individuals and lower for 10. Curiously, for the two Greenhorn Mountain samples and the' Havilah sample, pooled, the ratio was 33:4, while for the Walker Basin, Tehachapl and Lebec sam- ples, also pooled, it was 7:6. The difference between the ratios 33:4

12

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/, Re$. tepid.

and 7:6 is statistically significant (p=0 02) desoite the small numbers in the latter. It is possible that the tendency for the marginal row of spots to be less silvered than the disc spots is linked to the general lack of silvering in the three northernmost localities.

TABLE 2. Frequency distribution of silvering scores

Sex and sample Score

0 1 ' 2 3 4 5 6 Mean Scored Total

Males :

A. E. slope. Greenhorns 5 3 1 1—2 1 3.16 — - 19

B. W. slope, Greenhorns 17 8 7 64 8 7 2.42 7 64

C. Havilah 2 1 — 2 — 2 4 3.73 4 15

D. Walker Basin 1 2 1 — 1 2 19 5.08 4 30

E. Tehachapi 1 — — - i— _ — 13 5.40 — 15

F. Lebec 1 1 1 1 1 1 39 5.54 15 60

G. Sandberg’s — — — — — . — 10 6.00 3 13

Total 27 15 10 11 6 15 99 4.16 33 216

Females :

A. E. slope, Greenhorns — 1- — ■ — — — -2.00 — ■ 1

B. W. slope. Greenhorns — — 2 3 - — — — 2.60 5

C. Havilah l l

D. Walker Basin _ „ _ 11 1 3 5.00 — 6

E. Tehachapi _ _ l 1 6 5.01 — 8

F. Lebec 1 _ _ _ 25 5.77 1 27

G. Sandberg’s - — — — . — — — 3 6.00 — 5

Total 1 — 4 5 1 i 39 5.12 2 53

The mean score for males is 4.16 and for females is 5.12 (Table 2), suggesting that females tend toward more silvering than males. But four-fifths of the females were taken at Walker Basin, Tehachapi and Lebec where silvering in both sexes is nearly complete. If we pool these three sampls and cHss together the individuals with scores 0 to 4 inclusive, and similarly those with scores 5 and 6, in order to have high enough numbers for statistical test, we find no significant dif- ference between the sexes (P = 0.9). Accordingly, further analysis deals with both sexes combined, as shown graphicallv in Fig. 2.

The arrangement of samples in Fig. 2 is in ascending order of their means. This also arranges them from north to south except for the reversal of samples A and B. Where samples are near the same par- allel of Latitude and have appreciable meridianal displacement, as among A, B and C as one group and F, G, and H as another, their means also ascend from west to east.

The slopes of the lines connecting the means in Fig. 2 should not be taken as representing gradients of silvering in the sense of reflecting unit increase of silvering per unit distance. The panels are not spaced in proportion to distance, but merelv to accommodate the height of the bars. The means, themselves, are defective because the scores do not represent even gradations in amount of silvering. Further, because of

t§€a

VARIATION IN SILVERING

13

wesr SLO PE. GREEN - HORN MTS. 35* 37' EAST SLOPE, GREEN - HORN MTS. 35® 43 '

HAVILAH 35® 31'

WALKER BASIN

3 5* 23'

TEHACHAP! 35®08'

LEBEC 34*50*

SA NDBERG'S 34® 45'

BOUQ UET CANYON 34® 35'

FIGURE 2. The degree of silvering of the several samples, shown as histo- grams of the number of individuals according to grade (see text); and the mean grades, shown as small circles connected with heavy straight lines.

NUMBER OF INDIVIDUALS

14

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J. Res. Lepid.

the prevalence of low numbers at the middle scores, the distributions depart widely from the bell-shaped normal probability curve and the par? metric test commonly applied to means would not yield reliable probabilities even if the means were not otherwise defective. The means were computed and connecting lines were supplied in the graph only to give a general perspective of the amount and direction of dif- ferences between localities.

For a more careful assessment, the significance of the differences between samples, as to the numbers of individuals falling into the sev- eral silvering classes, can be made by the chi -square test which re- quires neither a normal distribution nor uniform class size. It does require a pooling of the original score classes to provide a minimum of five as the expected number on a class. To meet this requirement, the data have been grouped into two classes: (1) individuals with Scores 0 - 4, which can be described as "unsilvered” and partly silvered”; and ( 2 ) those with Scores 5 and 6, which can be described as "silvered or nearly so”. With this grouping the approximate probability, P. of the difference between any two samples in respect of the ratio of "un- silvered and partly silvered” to "silvered or nearly so” occurring by chance can be found by entering the table of chi-square distribution on one degree of freedom with the value of chi scfuare computed from the 2x2 contingency table according to the method given by Fisher (1948, p. 85). For greater precision the Yates correction for contin- uity was incorporated and P was found by graphical interpolation be- tween tabular values. The results are given in Table 3 as a matrix in which the chi-square values betyeen all combinations of pairs of sam- ples are shown in the upper right portion and the corresponding values of P in the lower left portion.

TABLE 3. Chi-square values (upper right) and probability values (lower left) between pairs of samples.

Locality				Sample
and sample		B	A	C	D	E	F	G
W. Greenhorns ..	B		2.37	2.97	>10	>10	>10	>10
E. Greenhorns ..	A	0.16		0.02	4.63	1.10	>10	7.14
Havilah	C	0.08	0.10		1.24	1.74	0.83	1.78
Walker Basin	D	< .001	.03	.19		.01	.84	2.32
Tehachapi	E	<.001	.02	.18	.10		.64	1.36
Lebec	F	<.001	<.001	.34	.34	.40		.37
Sandberg’s —	G	<.001	.008	.02	.14	.19	.10

The three northern samples. A, B, and C form a group within which there is no statistically significant difference at the five per cent prob- ability level (P = 0.05), and the four southern samples, D to G, in- clusive, form another such group. But these groups are not discrete from each other. Sample C from Havilah differs no more significantly from D, E, and F than from A and B, indeed, somewhat less. The sum of chi squares among A, B and C is 5.36; df are 3; and P is 0.14. The

i(i):3-20, 1962

VARIATION IN SILVERING

15

comparable values among C, D, E, and F are: Chi-square, 5.34; df, 6; P, 0.48. The indeterminate position of Havilah relative to the two groups, most probably is due to the small number in the sample from there. With such a small sample it would require a very strong con- trast in silvering ratio to prove statistical significance. Until more ma- terial is available it remains uncertain whether the population at Havi- lah resembles more closely those to the North or those to the South in respect of silvering, or whether it is truly intermediate as suggsted by Fig. 2.

Likewise, the sample from the east slope of the Greenhorn Moun- tains is small and does not test significantly different from that of the west slope. But for the Greenhorn Mountains there are two sources of additional data. Thorne and I scored both his catch and mine while in the Greenhorns and this record includes about twice as many indivi- duals as given in Table 2. We used three categories: ' unsilvered”, *'part silvered”, and “silvered”, corresponding somewhat inexactly to the Scores 0 - 1, 2 - 4 and 5 - 6, respectively, of Table 2. Hovanitz (1934) reported the number of individuals in a sample from the east side of the Greenhorn Mountains, elevation 5500 feet, and from the west side at Cedar Creek, elevation 5000 feet, according to three cate- gories: “not silvered or very slightly so”, “intermediate” and “well - or fairly-well silvered”. Assuming these categories correspond approx- imately to those of Thorne-Sette, the data may be pooled as follows: East side:

	Unsilvered	Intermediate	Silvered	Total
Thorne - Sette .	......6	.15	17	38
Hovanitz	....0 ......	..2	14	16
Total West side:	...........6	17 .........	31	...54
Thorne - Sette ...	72	...24	32	128
Hovanitz	....10	8	4	22
Total ..............	.........82 ......	..........32	36	150

With more data it is possible to use a 2 x 3 contingency table for a more discriminating test. This yields a probability far less than one in a thousand that the west side and east side samples could have been drawn from a population containing the same proportions of unsil- vered, partly, silvered, and silvered members. This does not prove that there is no mixing between the populations of the west and east slopes; it only indicates the extreme unlikelihood of enough inter- change to form a thorough mixture. But when it is considered, in addition, that the ridge of the mountain is clothed with transition forest within which no colonies of callippe were found, it seems clear that the interchange, if any, must be slight and probably by way of mixing with the more silvered populations to the South at different rates on the two sides of the mountain range as suggested by Hovan- itz (1943, p. 411).

16

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Turning southward, past Havilah, there is at Walker Basin a small proportion of unsilvered and partly silvered individuals in the pop- ulation. The low proportion continues with only slight further dim- inution in going from Walker Basin in the Piute Mountains, through the Tehachapi Mountains to Lebec. This uniformity suggests a rela- tively brisk interchange between colonies in this stretch of mountains, probably coupled with strong environmental selection against unsil- vered individuals.

Then at Sandberg’s, only a short distance beyond Lebec, all indiv- iduals are silvered, This is true also for the specimens from Bouquet Canyon (not included in the scoring table because they were only a part of a series). But my sample from Sandberg’s is too small to assuredly include unsilvered or partly silvered individuals if they con- stitute only a small percentage of the population. There is historical evidence, in Gunder’s (1930) list of butterflies of Los Angeles Coun- ty, of the occurance of unsilvered callippe at several localities in the transverse ranges south and southeast of Lebec. Under ”Araynnis ma- caria lamina Wri. THE UNSILVERED MACARIA FRITILLARY, a transition form.” Gunder recorded one male collected by Comstock "June 10, 1922, Ridge Route;” one male collected by Friday "June 19, 1929, Pine Canyon;” and two males and one female collected by Gun- der "June 25, 1921, Bouquet Canyon.” "Ridge Route” probably is identical to, or at least near, the locality I give as "Sandberg’s”; "Bouquet Canyon” may be identical to, or near the locality of the Thorne col- lection here listed under the same place name; Pine Valley lies about half- way between the two. The last is definitely on the desert side of the transverse ranges, while the other two localities are near the crest divid- ing the drainage to the desert from the drainage to the Pacific. The Thorne collection is definitely from the Pacific drainage side. It is proba- bly that this crest marks the southern limit of the unsilvered or partly silvered form.

Reviewing, there is a mixture of unsilvered, partly silvered and fully silvered callippe extending through the Southern Zone of Inter- gradation, from the Greenhorn Mountains in the North, southward through the Piute and Tehachapi ranges, to the crest of the series of ranges extending transversely across California at about latitude 34° 40’ N. Most of the change from the predominantly unsilvered con- dition in the north to the predominantly silvered condition in the South, take place in about the northernmost one-fourth of the Zone. Through the remaining three-fourths, beginning at about the mid- length of the Piute Mountains, where a high degree of silvering al- ready has been reached, the increase in silvering is very gradual. Al- though it is still perceptibly incomplete at Lebec near the Southern end of the Tehachapi, unsilvered and partly silvered become so rare beyond there that one should not expect to encounter evidence of the unsilvered condition without drawing large samples from the popu-

(i):}-20, ip62

VARIATION IN SILVERING

17

lation. It is reasonable to conclude that this is the southern limit of the tendency toward lack of silvering in the ventral hind-wing spots of callippe. To express this finding in Fig. 1, the area shaded with lines slanted upward to the right should be extended to include localities E, F, G and doubtfully H. When so extended, the southern limit of lack of silvering would more nearly agree with the southern limits of "uniformly colored red-brown upper surface” and "lack of brown pig- ment between sdo<-s on the underside of the hind wings” as mapped by Hovanitz (1943, Figs. 2 and 4).

DISCUSSION

Although this description adds some details to the distributional pattern of silvering in callippe, it raises more questions than it an- swers. Some are concerned with geographic limits. How much far- ther north does silvering extend? Does it taper off gradually from the western Greenhorn Mountains northward as does the opposite condition from Walker Basin southward, or does it end abruptly a short distance north of the sampled Greenhorn Mountain localities? Does the more silvered population of the eastern slope of the Green- horn Mountains end as in a cul-de-sac co-terminal with the limits of the Kern River drainage, or does it extend northward as a tongue along the higher Sierra Nevada toward silvered populations such as those near Downieville and Gold Lake?

More perplexing questions concern the processes governing silver- ing. The distribution of individuals among the seven score classes re- veal a paucity of intermediates in the middle of the range (histo- grams A and C in Fig. 2 ) . Could such a frequency distribution arise from simple Mendelian inheritance, or is a more complex mechanism required?

The existance of intermediate deo:rees of silvering suggests sim- ilarity with the example of simple Mendelian inheritance described by Ford (1945, p. 173) for the Currant Moth, Abraxas grossulariata L., which, in its commonest form, has wings with a white bick.Erround. In its less comomn form, lutea Cockerell, the white is replaced by a deep yellow. When these two forms are interbred the heterozygotes have a pale yellow background. Mating an individual homozygous for white with one homozygous for deep vellov/, produces offspring inter- mediate between the two parents. There is no dominance. Taking this as a model for silvering in callippe, and using Ford’s system for notation we may use the symbols and for represen-

ting the unsilvered ( Score 0 ) , the partlv silvered ( Scores 1 - 5 ) , and the completely silvered (Score 6) phenotypes, respectively. For such a model, in a population containing equal numbers of the two homo- zygotes (C^C^ and OC^), we should find : C^C^:

1:2:1. None of our samples have equal numbers of homozygotes, but if we pool samples A, B and the ratio is 24 : 51 : 18. This

18

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/. Res. Lepid.

differs from the ratio 1 : 2 : 1 by no more than one would expect from random sampling variability in about half of the samples drawn (P =z 0.44). We may conclude that there is no evidence against the hypothesis that silvering is controlled by a single pair of alleles of the phenotypes scored 1 to 5 may be lumped as the heterozygous com- ponent of the population.

However, in the Currant Moth, equal doses for white and for deep yellow produced a color about half way between the two homo- zygotes. In callippe there are very few individuals about half silvered. Individuals scored 3 and 4 comprise less than one-third of the cate- gory with scores 1 to 5. Perhaps some more complex genetic system may account for this peculiar distribution within the partly silvered segment of the population. But I am attracted by the idea that some chemico - physical process, such as crystallization may be involved. These tend to be triggered by very slight differences in conditions, and once triggered, go to completion.

In this connection it is also interesting that in areas of potential silvering, the single scales, as viewed with a hand lense, appear either totally buff or totally silver, never in between.

In pursuing this idea, I have found only a little information on the silvery decorations of the Lepidoptera in the literature that bear on its chemical nature. Mayer (1897) makes direct reference to its nature in the Argynnids, saying ”... Dimmock ('83) has shown that the silvery white and milk-white colorations are due to optical effects produced by reflected light. In the silvery white scales, however, such as the under surface of the hind wings of Argynnis, there must be a reflecting surface toward the observor, for both silvery and milk- white colors appear simple milk-white by reflected light.” According to Fox (1953, p. 289) uric acid, derived from chrysalid metabolism, deposited in the wings of the adult butterfly; guanine and uric acid contribute opaque whiteness and glistening silvery aspects. Ford (1945), although discussing extensively the physical and chemical nature of butterfly coloration, is silent on the nature 'of silvering. Taylor, (1925) points out that guanine (also spelled guanin) deposited in crystalline form imparts the silvery appearance prevalently displayed by pelagic fishes, while bottom fishes with prevalently white under- surfaces have their "subdermal tissues heavily charged with amorphous guanin, which is chalky white.” He describes guanine crystals, after they have been processed into pearl essence for making artificial pearls, as ". . . very thin light blades, floating in a liquid . . . [which] show their maximum luster when they are oriented parallel to each other . . . [when] pointing promiscuously in all directions, the effect will be a metallic or dull pearly luster.”

While one would prefer evidence derived directly by analysis of the substance as it occurs in callippe, it is not far fetched to suppose that this substance is guanine, sometimes deposited as crystals disposed

t(i):3-20, i$6a

VARIATION IN SILVERING

19

with appropriate orientation to give the specular effect that we call silvery, and sometimes in amorphous form adding whiteness to the pigmental brown to produce the light buff of the unsilvered spots. On this supposition it is necessary that the "silvering gene” control only the conditions within the pupal scale-sac fluid so as to precipitate guanine amorphously for buff scales, or alternatively, as crystals for the silver scales. Presumably, in homozygotes the balance of influences is well to one side of the critical point so that the deposite in all scales is always amorphous, or always crystalline. In the heterozygotes, too, it may take place on the "all or none” basis, but by single scales. Under the equal and opposite influence of the two alleles the equilib- rium may be very unstable and readily tipped to one side or the other of the critical point. This could be mediated by very slight differences in environmental conditions of the particular microclimate of a pupal individual at the precise time of color deposition in the scale sacs. This would tend to affect nearly all of the scales of an individual alike, swinging most of them toward one side of the critical point more often than nearly equal numbers to each side. Small differences between members of the colony as to pupation site, date and time of day of deposition of salts in the wing sacs, or even the rate of drying after eclosion, might provide the variety of conditions necessary to produce the observed peculiar frequency distribution of the supposed hetero- zygous phenotypes.

This set of ideas is not advanced as an explanation, but as an hypothesis inviting test by those having interest and competence in the fields of experimental breeding or biochemistry, or both.

It is a pleasure to acknowledge the stimulus to undertake this analysis and the material help received from William Hovanitz; the generosity of Fred Thorne in giving specimens and sharing his uncom- mon collecting serendipity; and the kindness of Paul Grey in review- ing my identification of many hundreds of specimens of this and other Argynnids.

LITERATURE CITED

ABRAMS, LEROY. 1940-1951. Illustrated Flora of the Pacific States, vols. 1-3, 4 vols. Stanford.

ABRAMS, LEROY and R. S. FERRIS. I960. Illustrated Flora of the Pacific States, vol. 4, Stanford.

DOS PASSOS, C. F. AND L. P. GREY. 1947. Systematic Catalogue of Speyeria with designation of types and fixation of type localities. Amer. Mus. Novitates, no. 1370: 1-30.

JEPSON, W. L. 1923-25. A Manual of the Flowering Plants of California.

Berkeley. .

FISHER, R. a. 1948. Statistical Methods for Research Workers. Hafner, N. Y. 10th Ed.

GUNDER, J. D. 1930. Butterflies of Los Angeles County, California.

Bull. Sou. Calif. Acad. Sci. 29 (2) ; 39-95.

HOVANITZ, WILLIAM. 1941. Parallel ecogenotypical color variation in butterflies. Ecology 22: 259-284.

20

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1943. Geographical variation and racial structure of Argynnis callippe in California. Amer. Nat. 77:400-425.

MAYER, ALFRED G. 1897. On the color and color-patterns of moths and butterflies. Bull. Mus. Comp. Uool. Cambridge 30 (4) : 169-256.

RICKER, W. E. 1940. Relation of "catch per unit effort” to abundance and rate of exploitation. /. Fishery Res. Board Canada, Toronto.

TAYLOR, HARDEN F. 1925. Pearl essence: its history, chemistry, and technology. Appendix to: Rept. U.S. Commissioner Fisheries for 1923. Bur. Fish. Doc. 989. Washington, D.C.

1(1) :21.42, 1962

Journal of Research on the Lepidoptera

THE EFFECT OF VARIOUS FOOD PLANTS ON SURVIVAL AND GROWTH RATE OF PIERIS^

WILLIAM HOVANITZ AND VINCENT C. S. CHANG

California Arboretum Foundation, Inc., Arcadia^, Los Angeles State College,

Los Angeles and University of California, Riverside

The close relationship between most phytophagous insects and their host plants is a general phenomenon known by most entomologists. This relationship is so outstanding that field naturalists can often locate colonies of any particular insect most readily by first searching out the host plants, as they often are larger and more obvious to the eye than the insects themselves.

What is not so well known is ( 1 ) the extent to which it is possible for any particular species or race to survive on various food plants, and (2) the causes of the attraction to, and survival of, any race of insect on a particular plant.

It is the purpose of this paper to indicate something of the range of ability to survive of two insects, Pieris rapae and Pieris protodice, (the "cabbage or mustard "butterflies) on various cruciferous plants. In other papers, it is intended to go into the various aspects of the development of food plant preferences in insects, including its causes, evolution, and relationship to origin of phylogenetic groupings.

THE MATERIAL AND METHOD

The experimental work to be reported on here and in subsequent papers has been carried out in Arcadia, Southern California. All species of the genus Pieris (Lepidoptera: Pieridae) found in southern Cali- fornia have been utili2ed for the study. The geographical ranges and specific food plants of the species existing in southern California are being described elsewhere (Hovanitz, 1962) and the general distribu- tion of the species of North America in another paper (Hovanitz, 1962). Five species of Pieris exist in this area, P. rapae (a European immigrant), P. protodice, P. beckeri, P. sisymbrii and P. napi. Each of these occupies a specific habitat and is restricted to a different food plant.^

1 Aided by a grant from the National Science Foundation, Washington, D.C.

2The authors wish to express their great appreciation to Dr. W. S. Stewart, Director, Los Angeles State and County Arboretum for great cooperation in making this work possible.

3Some taxonomists consider Pieris occidentalis to be a distinct species separate from Pieris protodice, rather than a geographical race, ecological race or local phenotypic form. If this were the case, there would be six species in southern California.

21

22

HOVANITZ AND CHANG

/. Re$. Lepid.

Pieris rapae is the easiest species to breed under greenhouse condi- tions and has been used for most experiments. It aslo has a wider range of satisfactory food plants than the others. As a European immigrant, it remains restricted largely to plants of European origin and has never adapted itself under natural conditions to any American native. Contrariwise, Pieris protodice, a native species, has never adapted itself to any European plant grown in cultivation, but has assumed an "economic” role only in utilization of European plants (mustards) growing in semi-wild habitats. The other Pieris are restricted entirely to one or a few native species of plants.

The food plant tests were made in several series at different times of the year and with different species of plants. Each series was run for the purpose of comparing the influence of several plants (usually five) on growth rate and mortality. For each series, a group of twenty larvae, obtained as follows, were grown on each plant. Female Pieris rapae were allowed to oviposit on a kale plant in the greenhouse. For the first series, the eggs were removed from the kale leaf and placed on leaves of the plant being tested in a petri dish. On all other tests, the eggs .were allowed to hatch on kale, and to eat on it for one or two days before removal to the tested plants. In order to minimize the effects of variable environmental conditions, all tests of a series were grown at the same time and place. For example, eggs laid on September 11, 1959, were used for the first test. On September 14, 1959, the larvae were measured for the first time, and then successively thereafter each day until pupation. The dates of larval (or pupal) deaths were noted.

The later tests were similar except that (1) the origin of the parents was different, ( 2 ) one or two day old larvae were used instead of eggs, ( 3 ) the time of year and ( 4 ) place of breeding was different. Data on origin of the material for each test are indicated in Table 1.

TABLE 1 : Source of larvae used in these experiments.

Series	Species	Food Source	Locaiity ( coilected	Date Generations of experient from wild
			Western
1	Pieris rapae	Cabbage	Orange	Sept.11,1959	1
			County
2				Oct. 9,1959	2
3				Nov. 25, 1959	4
4				Feb. 20, 1960	6
5				Feb. 20, 1960	6
6				Aug. 2, I960	11
7				Sept. 19, I960	12
8	Pieris protodice	Mustard	Laguna Beach	Aug. 27, 1959	1
9		II	San Fernando
			Valley	July 18, 1960	1
10		Cleome	Owens Valley	July 21,1960	1

i(t):2i-4S, 1962

EFFECT OF FOOD PLANTS

23

SERIES NO. 1

Series No. 1 was conducted for the purpose of comparing the effect of the following plants on growth rate, size and mortality: black mustard (Brassica nigra), garden nasturtium (Tropaeoum majus) , bladder pod (Isomeris arborea) and watercress {Nasturtium officinale) ( Table 2 ) . The females used for the source of larvae were obtained from an open cabbage field isolated from any other cruciferous food plant source and over which the adults were swarming in huge num- bers. The probability that they came from any other source is infinitesimal.

TABLE 2. Viability and growth rate of Pieris rapae grown on different kinds of food plants ( Series 1 ) .

Plant	Number	Number and percent of larvae died	Days from egg to pupation	Range of variation in larval growth
Nasturtium	20	16	30%	20	3
Kale	20	2	10%	12	2
Mustard	20	8	40%	13	3
Watercress	20	18	90%	17	1
Nasturtium	20	16	80%	18	5
Isomeris	20	10	50%	20	3

The mortality (Table 2. Series 1) was highest on watercress (90%), next highest on garden nasturtium (80%), then Isomeris (50%), mustard (40%) and least on kale (10%). The rate of development as determined by the first larva to pupate, was most rapid on kale (12 days), least rapid on Isomeris (20 days), and increasingly more rapid on nasturtium (18 days) , watercress (17 days) and mustard (13 days). The range in variation of larval growth was greatest for nasmrtium, since five days elapsed between the first larva to pupate and the last. The range as indicated in the table should be interpreted with the fact in mind that only a fraction of the original twenty larvae remained at the time of pupation. In other words, only two larvae pupated out of twenty that were fed on watercress. Had more survived, the range between the dates of pupation might have been greater.

The growth rates of the larvae on the various plants were obtained by measuring ten larvae of each group each day and obtaining the average length. These were then plotted and a curve drawn for each. These curves are shown in Figure 1.

Measurements of the larvae were started on the third day after hatching as they were so small prior to that time. However, great

■^It should be noted that the watercress used in these experiments was obtained by purchase in a food market while all other plants were grown in the laboratory. It has occassionally been found that despite repeated washings, insecticide residues may be present upon such commercial vegetables and that these may cause death of larvae feeding upon them.

24

HOVANITZ AND CHANG

I. Res. Lepid.

differences already were apparent between the larvae grown on the various plants. Those on kale were 4.7mm long as compared with those on Isomeris which were only 1.5mm long. Those on nasturtium were 1.8mm, those on watercress were 1.9mm and those on mustard were 3.9mm. The kale-group larvae were over three times the size of the Isomeris group larvae. Increase in size of the larvae on subsequent days was fastest v/hen the larvae were grown on kale, second fastest on mustard, and about equally as poor on each of the other three plants. The largest sized larva was that grown on Isomeris (24mm) as com- pared with that on kale (22.2mm) but after eight more days of larval life. Those on watercress and nasturtium pupated at 20mm and those on mustard at 17.9mm.

It appears that the greatest proportional size difference in the larval groups occurred during the first three days, but that most of the loss in size was later recovered by a longer growth period.

SERIES NO. 2

The tests of Series No. 2 were carried out in order to correct what were thought to be defects in the experiments of Series No. 1. These were two in number. The first was the high mortality in the eggs when they were removed from kale and placed on the other plants. This problem was averted by letting the larvae hatch on the kale plant before moving to the tested plants. The second presumed defect was the possibility of increased mortality of the very young larvae on the new plants, due solely to physical characteristics, toughness, etc. This was partially averted by allowing the larvae two days of feeding on kale before transference to the tested plants.

One change in food plant was made in this test: radish obtained from a food market was employed in place of watercress. Another inevitable change was the climatic condition under which the tests were conducted. They were changed slightly by the fact that the tests were carried out starting October 9, 1959, instead of

September 11, 1959.

TABLE 3. Viability and growth rate of Pieris rapae grown on different kinds of food plants (Series 2).

Days Range of

from variation egg to in

No. and % No. and % Total No. pupa- larval

Plant No. of larvae died of pupae died and % died tion growth

Kale	20	2	10%	0	0	2	10%	11	2
Mustard	20	2	10%	3	15%	5	25%	13	4
Radish	20	8	40%	5	25%	13	65%	13	5
Nasturtium	20	8	40%	2	10%	10	50%	14	5
Isomeris	20	12	60%	3	15%	15	75%	15	3

The mortality (Table 3) in this series was generallly not so high

PIER IS RAPAE

Growth rates of larvae of Pieris rapae grown on various plants ( Series No. 1 ) .

26

HOVANITZ AND CHANG

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as in the series just preceding, though that on kale was the same at 10%, those on mustard dropped from 40% to 10%, on nasturtium dropped from 80% to 40% and on Isomeris increased from 50% to 60%. Watercress was not tested this time but instead radish^ was used, with a resulting mortality of 40%. The better survival of these larvae is probably correlated with the fact that they were all grown during the first two days on kale.

Generally, the time (minimum days) to pupation in this series has been decreased (Fig. 2), The time on kale has been decreased one day, on mustard it remains unchanged, and on nastrutium and Isomeris it has been reduced five days. These reductions are probably correlated with the more successful survival of the young larvae on kale for the first two days, as compared with Series No. 1.

SERIES NO. 3

The tests of Series No. 3 are identical with those of Series No. 2 with the exception that they were started November 25, 1959 instead of October 9, 1959; in addition, the larv.ae by this time were four generations removed from the wild and inbred.

The larval mortality for all plants other than nasturtium was in- creased considerably in Series No. 3 compared with Series No. 2; 10% to 30% for kale, 10% to 35% for mustard, 40% to 80% for radish and 60% to 75% for Isomeris (Table 4). The data are com- parable for the percentage of pupae died.

TABLE 4. Viability and growth rate of Pieris rapae grown on different kinds of food plants ( Series 3 ) .

Days Range of from variation

Plant	No.	No. and % of larvae died	No. and % of pupae died	Total No. and % died	egg to pupa- tion	in larval growth
Kale	20	6	30%	0	0	6 30%	15	2
Mustard	20	7	35%	0	0	7 35%	16	5
Radish	20	16	80%	1	5%	17 85%	19	4
Nasturtium	20	7	35%	1	5%	8 40%	16	6
Isomeris	20	15	75%	2	10%	17 85%	18	8

The length of larval life has also been increased considerably in Series No. 3 tests, and thus also the range of variation in larval growth.

The reasons for these differences between Series No. 2 and No. 3 are probably two fold. First, the later time in the season has meant that the conditions of growth were somewhat different, primarily in the temperature.

The larvae were grown in a greenhouse in which the temperature was not well-regulated. Therefore, the temperature of the October

^The radish used in this particular experiment, but not in others reported on by us, was obtained in a food market. Refer to footnote (4) for possible latent effects.

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EFFECT OF FOOD PLANTS

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tests (Series No. 2) was higher than for the November tests (Series No. 3). This would profoundly influence the results insofar as the absolute growth rates are concerned. On the other hand, it did not affect the relative growth rates on the various food plants. These are still in the same descending order: kale, mustard, radish, nasturtium and Isomeris.

0 ■ I 1 ■ ! I I ■ ■ U— I I

U 2x 3 4 5m 6 r 8 9x )0 ItxK !2 13 14 15

DAYS AFTER HATCHING FROM EGG UNTIL PUPATION NO OBSERVATION

MX = NO OBSERVATION ON KALE

2. Growth rates of larvae of Fieris rapae grown on various plants (Series

No. 2).

The differential increase in size of the larvae on the various food plants is better shown in Series No. 3 (Fig. 3) than in Series No. 2 ( Fig. 2 ) . This is because the slower development rate served to exaggerate the differences between each strain. The larvae grown on kale grew larger at a faster rate than the larvae on any other plant, followed by mustard, nasturtium, Isomeris and radish. In Series No. 2, the order of the latter two were reversed. It is interesting to note that the ultimate size of the larvae which grew slowest was seldom equal to the size of those larvae which grew fastest. In fact, there is almost a direct relationship between these events.

A second reason for the difference between the mortality and growth data of these two series may be of genetic significance. The extent of inbreeding in the laboratory population by the fourth genera- tion would have been sufiicient to (a) increase the mortality, (b) slow

20 0 1_ P/ERIS RAPAE

HOVANITZ AND CHANG

J. Res. Lepid.

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(i):2i-42, 19^2

EFFECT OF FOOD PLANTS

29

development rate, (c) decrease size, (d) magnify the difficulties of feeding on abnormal plants by the simple means of decreasing overall vigor by the accumulation of allelic recessive lethal genes in the laboratory strain which had not yet had a chance to be eliminated by the selective effects of homozygosity.

SERIES NO. 4 AND 5

Series No. 4 was a test to compare various garden vegetables for their usefulness to Pieris rapae. These vegetables were mustard, kale, kohlrabi, broccoli and brussels sprouts. Series No. 5 was a similar test for various other plants. These were mustard (as before), nasturtium, radish, turnip and Isomeris. The tests were made in two series on February 20, 1962, using larvae following six generations of inbreeding, but of the same strain as used heretofore. In both of these tests, the larval mortality was higher on comparable plants used in previous tests. This again was probably due to the effects of inbreeding.

TABLE 5. Viability and growth rate of Pieris rapae grown on different kinds of food plants (Series 4).

Days Range of from variation

Plant	No.	No. and % of larvae died	No. and % of pupae died	Total No. and % died	egg to pupa- tion	m larval growth
Mustard	20	9	45%	0	0	9	45%	15	9
Kale	20	5	25%	2	10%	7	35%	15	10
Kohl Rabi	20	9	45%	0	0	9	45%	14	9
Broccoli	20	9	45%	0	0	9	45%	14	9
Brussels Sprouts	20	10	50%	0	0	10	50%	14	9

In Series No. 4 (Table 5), the data show that the larvae on kale had the lowest mortality rate (25%) while all the other plant tests were about the same (45-50%). Despite this, however, larvae from kohlrabi, broccoli and brussels sprouts reached pupation ahead of those on kale or mustard.

TABLE 6. Viability and growth rate of Pieris rapae grown on different kinds of food plants ( Series 5 ) .

Plant	No.	No. and % of larvae died	No. and % of pupae died	Total No. and % died	Days from egg to pupa- tion	Range of variation in larval growth
Mustard	20	9 45%	0	0	9	45%	15	9
Nasturtium	20	19 95%	0	0	19	95%	16
Radish	20	14 70%	2	10%	16	80%	15	13
Turnip	20	13 65%	0	0	13	65%	15	4
Isomeris	20	12 60%	0	0	12	60%	18	14

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HOVANITZ AND CHANG

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In Series No. 5 (Table 6), the data show that the lowest mortality again was on mustard but with considerably higher mortality on the other plants: for example, 95% on nasturtium, 70% on radish and 60-65% on turnip and Isomeris. The length of larval life was longest on Isomeris (18 days) and about the same (15-16 days) on other plants. The range of larval growth period varied greater with radish and Isomeris than with any of the other.

4 5 6 7 ex 9 10 II 12 13 14 I5x . 16

DArS AFTER HATCHING FROM EGG UNTIL PUPATION tx^NO OBSERVATION)

4. Growth rates of larvae of Pieris rapae grown on various plants (Series No. 4).

The rate of increase in size (Fig. 4) was more rapid with broccoli, kohlrabi and brussels sprouts than with kale and mustard. It is believed that this may be correlated with a more turgid or water-content condi- tion of these plants as compared with the drier or stiffer condition of the kale and mustard. For some reason, in Series No. 5, also, the increase in size of the larvae was not up to expectations on the mustard since the larvae on radish, turnip and nasturtium all exceeded those on mustard in final size ( Fig. 5 ) .

SERIES NO. 6

Series No. 6 was tested on August 2, I960 with the use of larvae eleven generations from the wild. One new plant, {Cleome lutea) , was tested in this series, since this plant was found to be primary food plant for Pieris protodice in Owens Valley, California. Mortality data

PiERiS RAPAE

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EFFECT OF FOOD PLANTS

31

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Growth rates of larvae of Fieris rapae grown on various plants ( Series No. 5 ) .

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for kale , mustard, nasturtium and Isomeris, (Table 7) compared well with previous data obtained on these plants (Series 1, 2, 3, 4 and 5). Cleo7ne was only slightly less effective in maintenance of larval life, the mortality rate being 30% as compared with 20% for kale and mustard. The relative lengths of larval life and the range of variation in larval growth also compares favorably with previous data. The higher mortality as seen in Series 3, 4, 5 and 6 has here been reduced to nearly the level of Series No. 1 .

TABLE 7. Viability and growth rate of Pieris rapae grown on different kinds of food plants (Series 6).

Plant	No.	No. and % of larvae died	Days from egg to pupation	Range of variation in larval growth
Kale	20	4	20%	12	3
Mustard	20	4	20%	13	3
Nasturtium	20	10	50%	13	3
Cleome	20	6	30%	14	5
Isomeris	20	12	60%	18	6

The differences between growth curves for each of the plants tested has been greatly increased in this test as compared with earlier tests. The factors responsible for this are unknown but may be due to a reduced adaptability caused by increased homozygosis (Fig. 6).

The larvae on kale were larger than those of any other plant at all times during their growth period. Pupation occurred the twelfth day. The larvae grown on nasturtium were almost the same size as those grown on mustard, whereas in Series No. 1 (Fig. 1) the larvae on mustard grew faster and larger. The larvae on Cleome were fourth in size on any day, while those on Isomeris were fifth.

SERIES NO. 7

This series was conducted in order to place the plant Thelypodium affine into position relative to the other standard test plants in the laboratory. Thely podium affine is a native cruciferous plant from the desert regions which is not known to be a food plant of any Pieris species, though another Thely podium species is the food plant of Pieris dsymhrii.

TABLE 8. Viability and growth rate of Pieris rapae grown on different kinds of food plants ( Series 7 ) .

Plant	No.	No. and % of larvae died	Days from egg to pupation	Range of variation in larval growth
Kale	20	5	25%	16	3
Mustard	20	6	30%	17	4
T. affine	20	14	70%	22	5
Isomeris	20	12	60%	18	6
Nasturtium	29	8	40%	17	6

PIER IS RAPAE

■{1)121-42, 1962

EFFECT OF FOOD PLANTS

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DAYS AFTER HATCHING FROM EGG UNTIL PUPATION

34

HOVANITZ AND CHANG

/. Res, Lepii.

The tests of Series No. 7 (Table 8) were carried out on September 19, I960, using larvae after twelve generations of laboratory inbreeding and growing on kale. The larvae grew relatively well on mustard, kale and nasturtium. The effectiveness of Isomeris was as previously tested. Thely podium affine was the poorest of all these plants as far as effectively providing the larva with stimulation to feed.

The mortality of the larvae on T, affine was 10% compared with 60% on Isomeris, 40% on nasturtium, 30% on mustard and 25% on kale. The length of larva life was increased from 16 days on kale to 22 days on Thelypodium. The final size of the larvae was reduced from 22mm long on kale to only 18mm long on the Thelypodium larvae which survived. (Fig. 7).

GENERAL OBSERVATIONS ON PIERIS RAPAE TESTS

The seven series of tests on Pieris rapae larvae have indicated several significant points:

( 1 ) Larvae from strains grown previously on cabbage or kale have a lower mortality rate, have a faster development rate, and a greater size when grown on kale than when grown on any other plant tested. When similar larvae are grown on mustard, these factors are decreased slightly. The order of decrease for plants other than these two is in the order approximately as follows: nasturtium, Cleome, radish, Isomeris, and T, affine. Plants of the cabbage group: kohlrabi, broccoli and brussels sprouts, are about the same as cabbage or kale. Turnip is about the same as radish.

( 2 ) Higher mortality in the tests is generally correlated with a slower development rate, a delayed time to pupation and smaller size of the larva and pupa. There are some exceptions to this rule; for example, the final size of the larva may be as great when the growth rate was slow on one plant as when it was fast on another. This has been indicated, however, only for plants of the cabbage group.

(3) Mortality rates in the various test series have been variable. These variations in mortality have been thought not only to be due to the genetic effects of inbreeding but also partly to the changed environ- mental conditions encountered while the tests were conducted, such as lower temperatures, etc. of the changing seasons. Lower temperatures slow the developing rate, and increase the relative humidity. Increased humidity permits the larvae to be attacked by bacterial or viral diseases to a much greater degree.

SERIES NO. 8

Tests of Series No. 8, 9 and 10 were conducted with larvae of Pieris proto dice rather than with Pieris rapae.

The first series with this species (No. 8) was conducted on August 27, 1959, utilizing larvae one generation from the wild. The

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DAYS AFTER HATCHING FROM EGG UNTIL PUPATION ( NO OBSER V ATION

36

HOVANITZ AND CHANG

/. Res. Lepid.

females of the previous generation were obtained in a field of black mustard, not near any other source of food plant, and in which eggs and larvae were found on that plant. This is good' evidence that the natural plant utilized here as larval food was mustard.

In this series, the food plants tested as larval food were mustard, kale, radish, Isomeris and nasturtium. The mortality of larvae of Pieris protodice on these plants increased in the order just stated, namely, 10% on mustard, 20% on kale, 55% on radish, 55% on Isomeris and 95% on nasturtium (Table 9). Deaths in the pupa stage on kale, radish and Isomeris materially increased the total mortality before adult emergence. This was not increased on mustard.

TABLE 9. Viability and growth rate of Pieris protodice grown on different kinds of food plants (Series 8).

Plant	No.	No. and % of larvae died	No. and % of pupae died	Total No. and % died'	Days from egg to pupa- tion	Range of variation in larval growth
Mustard	20	2	10%	0 0	2	10%	10	2
Kale	20	4	20%	2 10%	6	30%	11	2
Radish	20	11	55%	4 20%	15	75%	13	3
Isomeris	20	11	55%	3 15%	14	70%	16	3
Nasturtium	20	19	95%	■— — -	19	95%	21

The length of larval life was greatly different on the various food plants, ranging from ten days on mustard, eleven days on kale, thirteen days on radish, sixteen days on Isomeris to twenty-one days on nastur- tium. This wide variation in length of larval life is greatly different from anything encountered with Pieris rapae. It would indicate a fundamental difference in food plant adaptability between these two species, Pieris rapae being much more versatile in its requirements than Pieris protodice.

The size of the larvae at various days after hatching (Fig. 8) indicates that the mortality data are in close correlation with the size increments of the larvae with respect to food plants involved. Larvae on mustard and kale increased to 24mm in length, those on radish, Isomeris and nasturtium to 20-2 1mm each.

SERIES NO. 9

Discovery that Pieris protodice utilizes Cleome lutea as a natural food plant in the Owens Valley prompted a series of tests involving this plant. Both Series No. 9 and Series No. 10 were carried on for the purpose of testing Cleome in comparison with other plants used as standards. Series No. 9 utilized Pieris protodice larvae bred from adults obtained from mustard fields in the San Fernando Valley while Series No. 10 utilized Pieris protodice larvae obtained from Cleome

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EFFECT OF FOOD PLANTS

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mrs AFTER HATCHING FROM EGG UNTIL PUPATION (NO observation = x j

38

HOVANITZ AND CHANG

/. Res. Lepid.

plants in the Owens Valley (Big Pine). There is no chance that the San Fernando population had access to Cleome but there is a chance that the Owens Valley population did have limited access to mustard.

TABLE 10. Viability and growth rate of Pieris proto dice grown on different kinds of food plants (Series 9).

Plant	No.	No. and % of larvae died	Days from egg to pupation	Range of variation in larval growth
Mustard	20	6	30%	14	3
Cleome	20	7	35%	14	4
Nasturtium	20	18	90%	17	2
Isomeris	20	8	40%	17	5

The Series No. 9 larvae (Table 10) showed highest mortality on nasturtium (95%), just as in Series No. 8, with the lowest mortality on mustard (30%), next highest on Cleome (35%) and then Isomeris (40%). This corresponds well with comparable data in Series No. 8.

The growth increment curves for this series are somewhat com- parable with the preceding series except for the one surviving larva on nasturtium which increased to a size greater than that attained by larvae on any other plant. The differences between the growth curves, however, are not as distinct and clear as in Series No. 8, perhaps because of temperature differences between the two. Cleome is almost as satisfactory as mustard as a food plant for these larvae. ( Fig. 9 ) •

SERIES NO. 10

This series was run almost contemporaneously with the preceding and involved larvae from the Owens Valley strain grown on Cleome. The mortality (Table 11) was lowest on mustard (20%), second

TABLE 11. Viability and growth rate of Pieris protodice grown on different kinds of food plants (Series 10).

Plant	No.	No. and % of larvae died	Days from egg to pupation	Range of variation in larval growth
Mustard	20	4	20%	11	3
Cleome	20	6	30%	12	5
Isomeris	20	7	35%	13	7

lowest on Cleome (30%) and then Isomeris (35%). There was a greater range of larval growth rates on this group of larvae on Isomeris than in any other group as well as the lowest mortality on this plant in any of the larvae tested. The growth increment curves for these larvae indicate that the larvae do not show much difference in their reaction to mustard and Cleome but that mustard is still slightly better, and Isomeris is always poorer. Final size of the larvae, however, was larger for the Cleome (23 mm) than for the mustard (22 mm) or the Isomeris (18 mm)'. (Fig. 10).

LEN6TH OF LARVAE (mm) LENGTH OF LARVAE (>

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EFFECT OF FOOD PLANTS

39

DAYS AFTER HATCHING FROM EGG UNTIL PUPATION

9. Growth rates of larvae of 'Pieru protodice grown on various plants (Series No. 9).

PAYS AFTER HATCHING FROM EGG UNTIL PUPATION

10. Growth rates of larvae of Pieris protodice grown on various plants (Series No. 10),

40

HOVANITZ AND CHANG

/. Res. Lepid.

GENERAL OBSERVATIONS ON PIERIS PROTODICE TESTS

The three series of tests on Pieris protodice have indicated several significant points: (1) Larvae from strains obtained from mustard or Cleome populations had equally good survival value on mustard plants. The following plants gave decreasing survival value to the larvae: (Series 8) kale, radish, Isomeris and nasturtium. (Series 9)

Cleome, nasturtiuna, Isomeris. (Series 10) Cleome, Isomeris. (2) Higher mortality in the tests is generally correlated with a slower development rate, a delayed time to pupation and smaller size of larvae and pupae.

DISCUSSION

The tests described in the preceding pages have indicated some significant information regarding the effect of various food plants on survival in two species of Pieris. The ability to survive on different food plants is not an all or none relationship, but rather is a relation- ship based upon relative ability to survive. In the most extreme case, all larvae may die rather than eat a completely unacceptable plant. On the other hand, plants may be placed in an order of desirability with regard to the ability of larvae to survive, or to grow satisfactorily, on plants which they may accept at least reluctantly.

The tests described in this report are based upon using three criteria to indicate the desirability of a plant to the larvae. The first of these is the ability to survive, or the reverse which is the mortality, expressed as a percentage of the total larvae which died during the experiment. The second criterion is the daily size increment during the life of the larva. This actually tests two factors: (1) the physiological usefulness of the food to the larvae and (2) the total amount of food eaten and uilized, which may be a direct result of the stimulatory activity of the plant toward the larvae. The third criterion is the range in variation of larval growth. The significance of this criterion is in more doubt than the other two, but the range indicated would in some degree show the genetic variability present in the larval population toward physio- logical adaptation to the particular plant.

The results just described show that some plants are much more suitable for larval food to certain larvae than are other plants. The reasons for this greater suitability are not made clear. In those cases where higher mortality, slower growth rate, size increments and final size are correlated, the cause of the poor growth could be lack of nutriment in the plant, or lack of larval ingestion of the plant. In other cases where larval mortality may be high, as with the broccoli, Kohl- rabi and Brussels sprouts tests (Table 5) hut growth rate rapid and size large ( Fig, 4 ) , there are probably two factors involved. The rapid increase in size could be due to a high attraction to a very nutritious plant, but secondary conditions surrounding the plant may be conducive

I (i):2i -42, 1962

EFFECT OF FOOD PLANTS

41

to a higher mortality, namely, high water content in the plant itself, or higii humidity surrounding tne plant whicn would increase the susceptability of the larvae to virus and bacterial intections.

Toughness of leaves of a plant cannot be ruled out as a factor involved in larval speed of growth. Some leaves are too tough for the larvae to feed upon easily. Leaves of the same plant vary in tnis regard; succulent leaves at the siioot apex are usually much more desirable than older, mature leaves. This may be caused by toughness, or it may be caused by the greater perception of attractive substances permeating from younger leaves. At any rate, the relative uniformity of the tests in the difterent series is good evidence for the conclusion that this factor has not been of major significance.

The greater ability of tieris rapae as compared with Pieris protodice to survive on a variety of common cruciferous plants is interesting in view of the fact that both succeed well on black mustard. Pieris rapae survives better on kale over mustard and P. protodice survives better on mustard over kale. However, on most other cruciferous plants tested, there was a wide disparity between their preferences. The selections made by the strains of larvae shown by these experiments complements perfectly the known differences in geographical and ecological distribu- tion of the two species concerned, and indicates that there is little natural competition between the species for food plants. This shows also why Pieris rapae is always associated with European cruciferous plants, weeds or truck crops, while Pieris protodice is generally associated with other cruciferous plants.

Takata (1957, 1959, 1961) has published a number of papers which bear upon this problem. None of these deals precisely with the effect of various food plants on survival and growth rate of Pieris, but rather deals only with selection preferences by the larvae and the adult. Further considerations of the relation of this work of Takata on Pieris rapae crucivora to the present general program will therefore be made in a complementary paper entitled "Three Factors affecting larval choice of food plant” to be published in this journal.

A visit to our project by W. H. Dowdeswell of England during the course of these experiments was followed by a similar study of more limited extent on Pieris napi L. in England. Dowdeswell found that two populations of this Pierid were feeding on different cruciferous plants. By switching the food plants in laboratory experiments on test- ing the larvae, he found as we had, that there was a higher mortaity and decreased growth rate when the larvae were fed on plants not the normal food plant for that population (Dowdeswell and Willcox, 1961).

SUMMARY

1. Tests were made of the ability to survive of larvae of two species of Lepidoptera, Pieris rapae and Pieris protodice on various food plants.

42

HOVANITZ AND CHANG

/. Res. tepid.

2. Three criteria were tested: (a) mortality, (b) growth rate and size increment, (c) range in variation of larval growth.

3. Seven series of tests involving Pieris rapae were conducted showing the results summarized under the heading "General Observa- tions on Pieris rapae Tests.”

4. Three series of tests involving Pieris protodice were conducted showing the results summarized under the heading "General Observa- tions on Pieris protodice Tests.”

5. Pieris rapae has significantly different requirements for food plants than Pieris protodice, even though the tested larvae were both from mustard-bred strains.

6. The native adaptability of Pieris rapae to survive on various plants is better than that of Pieris protodice.

7. The causes of differences in survival value of the larvae on different food plants are believed to be several, but the main one is the total amount of food eaten and utilized.

LITERATURE CITED

DOWDESWELL, W. H. AND H. N. A. WILLCOX. 1961. Influence of the food plant on growth rate and pre-imaginal mortality in the green-veined white butterfly Pieris napi (L). Entomologist 94:2-8.

HOVANITZ, W. 1962. The ecological and geographical distribution of Pieris species in Southern California. J. Res. Lepidoptera 1 : in press. HOVANITZ, W. 1962. The distribution of the species of the genus Pieris in North America. J. Res. Lepidoptera 1 ( 1 ) : this issue.

TAKATA, N. 1957. Studies on the host preference of cabbage butterflies {Pieris rapae L.) III. Mechanism of food preference of cabbage butterfly larvae. Jap. J. Ecol. 7 (3) :117-119.

TAKATA, N. 1959. Studies on the host preference of common cabbage butterfly, Pieris rapae crucivora Boisduval. IV. Tendencies of food prefer- ence in relation to total quantity of the host plants cultivation. Zoological Magazine (Japan) 68(5) : 187-192.

TAKATA, N. 1959. Studies on the host preference of common cabbage butterfly, Pieris rapae crucivora Boisduval. VI. Change in the food preference of larvae when reared successively by the definite food plant for several generation. (Preliminary report) Jap. J. Ecol. 9:224-227. TAKATA, N. 1961. Studies on the host preference of common cabbage butterfly, Pieris rapae crucivora Boisduval. XI. Continued studies on the oviposition preference of aduir butterflies. Jap. J. Ecol. 11 (3) :124-133. TAKATA, N. 1961. Studies on the host plant preference of the common cabbage butterfly, Pieris rapae crucivora Boisduval. XII. Successive rearing of the cabbage butterfly larva with certain host plants and its effect on the oviposition preference of the adult. Jap. J. Ecol. 11(4): 147-154.

Journal of Research on the Lepidopvera

l(l):43-49, 1962

GENERAL CHARACTERISTICS OF THE MOVEMENTS OF VANESSA CARDUI (L.)

J. W. TILDEN

San Jose State College, San Jose, Calif.

It is a matter of common knowledge that the populations of many species of butterflies participate in large and extensive mass movements. While several workers, notably C. B. Williams of England, have done extensive work in this field, relatively few investigators have made it their principal subject of research. Though much pertinent information has been assembled and certain tentative con- clusions may be reached, it cannot be said that the movements of butterflies are as well understood as certain other phases of the study of these insects.

Most movements of butterflies, while usually referred to as migra- tions, would not meet the criteria set up by students of vertebrates for defining migrations. The migrations of birds, for example, involve cyclic movements. There is a going out and a return. Few butterflies other than the Monarch [Danaus plexippus (L.)], habitually possess such a rhythmic pattern of movement. Even with the Monarch, the individuals that return are usually (probably always) not the same individuals that initiated the outward movement, but are the offspring of these original individuals.

Many movements of butterflies are relatively local wanderings, and may be in one direction in one local area, but in a different direction in another area a relatively few miles away. For example, in the fall of I960, Tilden noted Libytheana hachmanii (Kirt.) (the Snout Butter- fly) moving southwesterly in large numbers in the vicinity of Con- tinental, Pima Co., Ariz., on Sept. 14. The next day, Sept. 15, equally large numbers of this species were observed moving up-canyon ( north- ward) in Sycamore Canyon, Santa Cruz Co., about thirty -five miles south of Continental by air line, though considerably further by road.

The very conspicuous movements of certain species have been regarded as depending on population pressures, leading to a mass exodus. These may be considered as emigrations from the populated area, and as immigrations into surrounding area. Such movements frequently appear to be in one direction only. Unless the insects were to find suitable conditions at the far end of the movement, establish-

43

44

TILDEN

/. Res. Lepid.

merit would not result. Such movements have been thought to account in part for the finding of strays far beyond the normal ranges of the species.

Movements of an altitudinal nature have been observed. Nymphalis calif ornica (Bdv.) has been seen ascending the Sierra Nevada of California in great numbers. Such movements may result in finding sufficient larval food plants for a subsequent brood. In I960, Tilden found this species in outbreak numbers of adults at Manzanita Lake, Lassen Volcanic National Park, Calif., on June 10-17. Numerous larvae in various stages of development were found on Ceanothus spp. Adults could be observed many miles below the Park, working their way up the mountain. It may be significant to note that this species passes the winter as an adult. It seems plausible that these altitudinal move- ments of adults are the usual way for adults to reach the higher eleva- tions, where they act as parents of a late high elevational brood. This might be a fruitful field of investigation.

The often spectacular "migrations” of Vanessa cardui (L.) present an interesting condition somewhat intermediate between true migra- tions and other types of movements. Return movements seem not to be clearly documented in regard to this species. However, reproduction has been observed repeatedly along the route, and the offspring take up the movement when they emerge as adults. These mass movements of Vanessa cardui thus proceed in periodic waves, alternating with relative lulls between, and the whole process has much more continuity than is characteristic of the movements of most other butterfly species.

Much of the basic work on the movements of Vaness-a cardui has been done by C. H. Abbott. Others, including Sudgen, Woodbury and Gillette in Utah, have made contributions. Among the various titles that form the literature on the movements of this species in western United States, some are short observational notes only. Others present a considerable amount of detailed study. Abbott has attempted to understand the nature of these movements and has produced several penetrating papers on the subject.

The last great movement was in 1958. Abbott traces three or more generations extending up to or beyond the Central Valley of California. Other generations carried the waves through the Bay Region of California on into Oregon. The generations involved in the northern portions of the movement become less clear.

The first generation seems to have originated in northern Mexico, the second in the Imperial Valley of California, western Arizona and the eastern Mohave Desert of California, the third in western Mohave Desert, and the fourth in the Central and Coastal Valleys of California, and to the Bay Region. Abbott (1959) has presented material that includes the observations of a number of workers, and has coordinated this material. In addition, the follov/ing observations are here presented for the first time.

j(i):4}-49, 1962

MOVEMENTS OF VANESSA

45

Tilden found many dead adults in western Arizona (Mohave County) and in the vicinity of Needles, California, as well as large numbers of moving adults, March 30-31, 1958. From Barstow, San Bernardino Co., west to Mohave, Kern Co., great numbers of adults were flying northwesterly on March 31. Later that day adults were seen moving through Tehachapi Pass, Kern Co., and spilling into the San Joaquin Valley east of Bakersfield, Kern Co. On April 20 to May 9, eggs and larvae were abundant in the Salinas Valley, Monterey Co.

On May 30 - June 1, Tilden found large numbers of adults along the Redwood Highway (Route 101) between San Rafael, Marin County, and Cloverdale, Sonoma County, moving northwesterly. Dead adults were seen as far west as Booneville, Mendocino County, where but a few living adults remained. This may mark the western edge of the movement.

In the vicinity of The Geysers, Sonoma County, adults were moving northwesterly in large numbers in overcast weather (fog) on June 1, before noon. Larvae were abundant on Amsinckia (Fiddleneck) and on the introduced Spanish Thistle ( Carduus ) , in various stages of development.

Two interesting reports were from Oregon. Ray Albright reported large numbers of Vanessa cardui moving in a north-north-easterly direction on May 18-19, 1958, while on May 20-21, equally large numbers were observed moving in exactly the opposite direction. He attributes this reversal of direction to the insects meeting a cold front, since a storm was in progress some distance beyond the place toward which the insects were noted to be flying. The other report was from David Huntzinger at Crater Lake National Park. He noted that Vanessa cardui was abundant there in 1958, though scarce or absent in 1957.

On April 1, 1958, Tilden observed what is apparently a new observation for the United States. Large numbers of Vanessa cardui were flying north-westerly in the rain. Between Vidal, San Bernardino County, and Desert Center, Riverside County, the rain was light to moderate, but rather cold. Between Indio and Whitewater Canyon, later the same day, the flight still continued in heavy to very heavy rainfall. This seems to indicate that adults may continue to fly, once on the wing, even in heavy precipitation. It would seem a priori that initiation of a flight during rain might be less likely.

From observations so far recorded it is possible to generalize on some of the characteristics of the movements of Vanessa cardui. Some of these generalizations have been set forth by Abbott and others, while some are suggested here for the first time.

1. The adults tend to fly into the wind. This may be a key point in attempting to explain the prevailing direction of the movements. During the time of year when Vanessa cardui is moving, the prevailing winds in California are north-westerly, and the movements of the

46

TILDEN

/, Res. Lepid.

butterflies are also in a north-westerly direction, almost or quite directly into the prevailing winds. Sudgen, in 1937, noted a northerly direction of flight in Utah. Sudgen, Woodbury and Gillette, in 1947, noted a north-easterly direction of flight. Observations to be made in the future might very well take special note of the wind direction as well as the direction of the insects’ flight, to find how complete this correlation between wind direction and flight direction may be.

2. The adults move at a rather equal velocity in relation to one another, resulting in a fairly constant spacing of the individuals. There have been some observations made where this did not seem to be the case, but for the most part, this generality seems to hold.

3. The insects tend to fly over obstacles rather than around them. At times this appears to the observer quite amusing, even ridiculous. If a tree, building or parked car obstructs the route, the adults fly over the top of the obstruction, when in some instances it would appear that a veering to the right or left would be more easily accomplished. The obstruction, whether it be low or tall, is barely cleared. On March 30, 1958, Tilden observed them piling directly over a small building near Barstow, San Bernardino County, the only building for miles in an open desert.

4. The adults tend to fly at rather even densities. If a line is marked off between tv^o points, fifty or one hundred feet apart, and the insects crossing this line per minute are counted, the results from several one minute counts are surprisingly similar. If then, the observer drives his car several miles, sets up another station and makes another series of counts, the results will again be similar, and frequently quite close to those of the previous station. But in widely separated areas, the count may be very different. That is, while the density on the Mohave Desert, for instance, may be quite constant, counts made in San Diego County at another time might indicate a different density. Further study may shed light on the possibility that density of flight is related to density of population.

5. Vanessa cardui adults will fly in overcast, at least after the movement is under way. This has been observed between Victorville and Needles, San Bernardino County, March 31, 1958, and near The Geysers, Sonoma County, May 31 and June 1, 1958.

6. They have been observed once at least in the United States (vide supra) to fly in large numbers during moderate to very heavy rainfall.

7. The migrating individuals are all of one species. Other species of butterflies do not seem to become involved in the mass movements of Vanessa cardtii.

8. The individuals in the flights are of both sexes. This was noted independently by sampling in 1958, by both Tilden and O. E. Sette. The sex ratio of the insects when engaged in a flight is very nearly the same as that oi Vanessa cardui at any other time, 0.5 or one half

i(i):43-49> 1962

MOVEMENTS OF VANESSA

47

of each sex. Tilden took a sample of fifty adults, and found twenty- seven males, twenty-three females. The numbers taken by Sette are not recorded. This phase of the investigation deserves further study and this is planned for the future.

9. The females from the above sample were not greatly gravid. None had eggs ready to oviposit. This suggests that the females may drop out of the flight when ready to oviposit. If this be true, it might explain the tendency to reproduce along the flight routes.

10. The total movement proceeds in waves, or phases, which so far appear to be based on broods, a conclusion which seems to be well supported by the work of Abbott.

In the light of current findings, it is possible to reconstruct, at least to some degree, the nature of the populations of Vanessa cardui during and prior to the flights.

1. The first (initiating) brood apparently originates to the south, in northern Mexico or southwestern Arizona.

2. Findings from those movements that have been studied indicate that large flights can occur only in years when there has been sufficient rainfall on the deserts for a large growth of vegetation, enough to support such populations of Vanessa cardui.

3. The food plants in the desert areas, as noted by many observers, are principally Boraginaceae, especially Cryptantha, but also Amsinckia. Malvaceae have also^ been reported. Thistles and other composites seem to be of little importance at this time.

4. Upon emergence of the adults, each succeeding brood begins to fly into the wind, which in the deserts of California at this season (early spring) results in a north-westerly direction of flight.

5. These adults reproduce at some point along the line of flight. Time and place of reproduction presumably depend on the condition of the insects and the presence of suitable vegetation. Information on how far the females fly before reproducing, and the precise reason for selecting a certain place for reproduction, would add much to our knowledge.

6. Four to five broods, perhaps more, succeed one another before the force of the movement is spent.

7. The northern extent of the movement is at least to the San Francisco Bay Region of California. In some years, such as 1958, the effect extends into northern California, and apparently further, to Oregon and perhaps even Washington. Information as to the relation- ship between the Vanessa cardui in California and those in Oregon and Washington during such outbreak years is badly needed.

Williams and Abbott have raised the question as to whether Vanessa cardui is found north of the Imperial Valley, Imperial County, Calif., in any but outbreak years. There seems to be good evidence that it is. An examination of pinned specimens from many parts of California shows specimens taken in almost every year for many years

48

TILDEN

/. Res. Lepid.

back. As a Professor at San Jose State College, Tilden has examined hundreds of student collections over a period of fourteen years, and has also examined other specimens dating back to 1920. Some speci- mens of Vanessa cardui appear in student collections every semester. It is evident that this species is a normal component of the butterfly fauna in many parts of California. It is probable, however, that this local endemic population has little or nothing to do with the mass movements which from time to time are superimposed on it.

Two other items seem worth mentioning. Firstly, moderate to large populations of Vanessa cardui may be found late in the fall at high elevations in the mountains of the western United States. Specifi- cally, Tilden found hundreds of adults at Hannagan’s Meadows, White Mountains, Arizona, September 12, I960. A fair population was found at Barton Flats, San Bernardino County, Calif., in September, 1957. Similar populations have been reported from the Sierra Nevada of California and elsewhere. The nature of these populations is not known, but it would seem that they are independent of the populations concerned with the great flights that occur in certain years.

Secondly, the mass flights of Vanessa cardui are of a very irregular nature. They are not regularly cyclic and do not occur at predictable intervals. However, some success in predicting these flights has been possible through knowledge of rainfall on the desert. Several workers foresaw the 1958 outbreak in the gathering populations of the south- west deserts.

An interesting and provocative suggestion of how rainfall may be necessary for mass movements of this species, was observed by Tilden September 11, I960, at Yucca, Mohave County, Arizona. Late summer rains were plentiful and vegetation was well developed. Numerous freshly emerged adults of Vanessa cardui were present, and reproduc- tion was in progress, with larvae of various stages on Cryptantha. It seemed that the basis for a movement was all prepared. However, the winter rains did not materialize, and on March 26, 1961, the area around Yucca was dry and no Vanessa cardui were to be found. If this abortive season is contrasted with the abundant rainfall of 1958 over the entire area, it points to a dependence of these populations on ample winter rainfall in the areas that are far enough south to act as reservoirs for populations that can engage in a mass flight.

Several questions are raised : ( 1 ) Why do these insects move at

all, rather than remaining where they are? Possibly food may become ^scarce, but populations exist that do not move out in such a systematic manner under lowered food conditions. (2) Why is the flight directed? Why do not these insects move randomly in any direction open to them? The tendency to fly into the wind may be a clue here. Or have such movements been repeated so many times over the history of the species, that the tendency to fly in one direction has been selected for? (3) What causes the adults to reproduce here and there along the

(i):43-49< ^9^2

MOVEMENTS OF VANESSA

49

route? Why do they not merely fly on until exhausted? Present information may suggest some tentative answers, but such answers, while plausible, are not yet supported by suflicient data.

The author would add that this attempt at a synthesis of our knowledge concerning the movements of Vanessa cardui in western United States is prompted more by interest on his own part than by a desire to inform others. The purpose of this paper is to bring into focus our ignorance of the real basis of this interesting phenomenon, with a hope that future work will help to clarify some of the little known facets of the problem.

LITERATURE CITED

ABBOTT, C. H. 1941. The 1941 migration of the painted lady butterfly, {Vanessa cardui) in southern California. Bull. Ecol. Soc. Amer., 22:13.

— — — 1946. Mapping the 1945 migration of Vanessa cardui in southern

California. Bull. Ecol. Soc. Amer. 27 :49.

— — 1950. Twenty-five years of migration of the painted lady butterfly,

Vanessa cardui, in southern California. Pan-Pac. Ent., 26:616-172.

— - 1951. A quantitative study of the migrations of the painted lady

butterfly, Vanessa cardui L. Ecol. 32:155-171.

— — 1959. The 1958 migration of the Painted Lady Butterfly, Vanessa

cardui (Linnaeus), in California. Pan-Pac. Ent., 35:83-84.

ESSIG, O. E. 1926. A butterfly migration. Pan-Pac. Ent., 2:211-212.

SMITH, RAY F., & E. GORTON LINSLEY. 1945. Migration of Vanessa cardui (Linn.). Pan-Pac. Ent., 21:109.

SUGDEN, JOHN W. 1937. Notes on the migrational flights of Vanessa cardui in Utah. Pan-Pac. Ent., 13:109-110.

SUGDEN, JOHN W., ANGUS M. WOODBURY & CLYDE GILLETTE. 1947. Notes on the migration of the painted lady butterfly in 1945. Pan-Pac. Ent., 23:79-83.

WILLIAMS, C. B. 1958. Insect Migration, xiii -f235 pp., 11 plates, 22 photos, 49 maps & diagrams. Collins, London.

WOODBURY, ANGUS M., JOHN W. SUGDEN & CLYDE GILLETTE, 1941. Notes on migrations of the painted lady butterfly in 1941. Pan-Pac. Ent., 18:165-176.

Journal of Research on the Lepidoptera

1(1) :51-61, 1962

THREE FACTORS AFFECTING LARVAL CHOICE OF FOOD PLANT’

WILLIAM HOVANITZ AND VINCENT C. S. CHANG"

California Arboretum Foundation, Inc., Arcadia, Los Angeles State College, Los Angeles and University of California, Riverside

Prior to the initiation of comprehensive tests of the attraction by larvae of Pieris rapae of various food plants, a number of prelim- inary trials were made to test the effect of external factors which might influence the correctness of these tests. Of the factors which were thought most important, the following were selected for trial:

( 1 ) Influence of direction of air movement ( "wind”) .

(2) Influence of age (size) of larvae.

(3) Influence of food previously eaten by larvae, or strain of larvae.

EFFECT OF WIND MOVEMENT

An experiment devised to test this factor was set up as follows: A nursery flat about 24 inches square was filled with vermiculite. Pots of plants, each about the same size, were placed in the vermiculite spaced about as shown in Figure 1. The table under the flat was marked A, B, C and D. The direction of the wind movement was at side B. In the tests, larvae were placed in the central area, shown by a small circle and allowed to go to the plants, or to leave the flat.

Ten different larvae were used for each experiment, and these were used a total of ten times each. Thus, each experiment involved 100 trials.

The wind direction relative to- the position of the plants was

changed by turning the flat by 90° after each 100 trials, as shown by the illustration (Fig. 1). The first position tested was with mustard toward the dirction from which the breeze came ( side B ) . The results of the preferential selection by the larvae are shown on Table 1.

Kale was selected by 19%- of the larvae, mustards by 56%, radish

1 Aided by a grant from the National Science Foundation, Washington, D.C.

2The authors wish to express their great appreciation to Dr. W. S. Stewart, Director, Los Angeles State and County Arboretum, for great cooperation in making this work possible.

51

52

HOVANITZ AND CHANG

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TABLE 1. The effect of wind movement on the choice of food plants by larvae of Pieris rapae

	Kale	Mustard	Radish	Nasturtium	Isomeris	None	Total no. of trials
	A 19	B56	C18	D3	D 1	3	100
90°	D20	A 20	B52	C4	C2	2	100
90°	C43	D25	A 26	B2	BO	4	100
90°	B53	C 15	D13	A8	A5	6	100

Ten 14.1 mm to 15.7 mm kale-bred larvae of Pieris rapae were used per test with each test ten times at each position. The parents of the larva were collected at western Orange County in a cabbage field.

by 18%, nasturtium by 3% and Isomeris by 1%. Larvae which left the flat without selection amounted to the additional 3%.

With the flat turned 90” so that the radish was now in position B ( in the direction of the wind ) , the selection results were very different. Kale remained relatively unchanged at 20%, mustard dropped from

(i);5i~6i, 1962

THREE FACTORS

53

56% to 20%, radish rose from 18% to 52% at position B, while the remainder were unchanged.

With a further 90° turn in the direction of the arrows (Fig. 1), the radish plant was now opposite the direction of the wind, and nasurtium-Isomeris was toward the wind. Kale at position C to the right side now rose from 20% to 43%, mustard at position D (away from the wind) rose slightly and v/as now 25%, radish at the left side was now 26% and nasturtium-Isomeris (toward the wind) was still relatively unchanged at 2 % .

The final 90° turn placed kale in the position toward the wind. Here, 53% of the larvae went to kale, 15% to mustard (right side), 13% to radish (opposite side), and 13% to nasturtium-Isomeris

(left side) .

CONCLUSIONS:

( 1 ) Of the four sides of the flat which could face the direction of the wind, the plants on that side were favored in three of the four arrangements, namely, mustard, radish and kale. Only when the nasturtium-Isomeris combination v/as toward the wind was the fre- quency in position B not increased. In fact, at that time, it was decreased.

(2) These tests, of course, cannot indicate which of the three favored plants are relatively more favored since they each received about the same percentage of selection when toward the wind. However, when away from the wind, radish received fewer selections than either kale or mustard.

(3) The Isomeris-nasturtium combination received its highest selection when in position A (left side). In this position also, more larvae left the flat without a plant selection than in any other position.

(4) The higher selection of kale (43%) while at position C (right side), than radish (26%) while at position A (left side) seems to indicate a preference for kale rather than for radish.

( 5 ) The lowest selection for the nasturtium-Isomeris combination was when it was in position B (toward the wind). This would seem to indicate that these plants (and Isomeris especially) repel rather than attract larvae of Pieris rapae.

(6) The data indicate that the direction of wind movement is of great importance in larval selection of food plant, since in all cases where the plant has a positive effect on selection, that position in the direction of the wind has by far the greatest selective influence. It is apparent that the reverse is also true, that if a plant is repellent, the effect is greatest when the wind comes from that direction.

[NOTE: The differences between the figures indicated are so great that the element of chance being involved is negligible. A chi-square test on the first trial gives a probability of less than one in a million that the differences are due to chance alone.]

54

HOVANITZ AND CHANG

/. Res. Lepid.

EFFECT OF LARVAL SIZE ON PLANT SELECTION

Tests for the determination of influence of larval size on plant selection were made in the same manner as indicated previously, except that all tests were carried out in a room with no wind or breezes. Nevertheless, the flat was turned 90° three times for each test. This applies to all subsequent tests for the sake of safety. Two . series of tests were made, using larvae of different origin.

The first series of tests (Table 2) was carried out with the use of kale-bred larvae. Larvae of different ages and sizes (size is roughly proportional to age) were separated and measured. Four larvae were isolated, these being the following sizes:: 8.4, 14.7, 19.0 and 21.0 mm in length. The tests were carried out by five trials of a given larva at each position with respect to the direction of the wind (Fig. 1), giving a total of 20 trials for each size larva.

TABLE 2. Choice of five kinds of plants by different sized larvae of Pieris rapae ( Series 1 )

Size of Total

larvae The number of times and percentage larva goes to Number

(mm)	Kale	Mustard	Radish	Nasturtium	Isomeris	None	of trials
21.00	16- — 80%	4—20%	0— 0	0—0	0—0	0—0	20
19.00	13—65%	3—15%	3—15%	1—5%	0—0	0—0	20
14.70	11—55%	4—20%	4—20%	1—5%	0—0	0—0	20
8.40	10—50%	5—25%	5—25%	0—0	0—0	0—0	20

One single kale-bred larva was used for each size; tested each larva five times at each position.

The 8.4 mm larva selected kale 50%- of the time, radish 25% of the time and mustard 25% of the time.

The 14.7 mm larva selected kale 55%, mustard 20%,. radish 20% and nasturtium 5 % of the time.

The 19.0 mm larva selected kale 65%, mustard 15%, radish 1 5 % and nasturtium 5 % of the time.

The 21.0 mm larva selected kale 80% and mustard 20% of the time and no others.

The probability, as caculated by chi-square, that the differences as indicated might be due to chance are less than 1/million, 1/100,000, 1/500, 1/500 respectively for each experiment.

CONCLUSIONS:

( 1 ) The increase in selection of kale for each experiment is correlated with increase in size of the larvae ( Fig. 2 ) .

(2) Kale is the plant selected over all the others in this experi-\ ment. It should be noted that the larvae had been bred on kale prior to the experiment, and previous generations had been bred on cabbage.

(3) Not one larva went to Isomeris'. This is interesting in view of the observation in the preceding experiments that Isomeris was

(i);5i-6i, 1962

THREE FACTORS

55

2. The relation between size (and age) of larvae and the percentage of the time kale was selected. The size of the larvae is directly correlated with an increase in selection of kale.

repellent to Pieris rapae larvae.

(4) The older or larger the larvae, the greater the selection of kale over all other plants ( Tig. 2 ) . The relationship is not a straight- line, but rather a geometric increase. This indicates that there is an increase in the critical powers of food perception in the older or larger larvae.

In the Series No. 2 tests (Table 3), larvae were used which had previously been grown on nasturtium. They were obtained from Ventura County on nasturtium and were continued in the laboratory on that plant.

Two larvae 22.4 mm in length, and four larvae 16.5 mm in length were used in this experiment. Otherwise, the trials were managed in the same way as in previous experiments with the exception that the total number of trials was 80 for large larvae and I6O for the

56

HOVANITZ AND CHANG

/. Res. Lepid.

smaller larvae.

The selection by these larvae bred on nasturtium (Table 3)' was radically different from the selection by larvae bred on kale ( Table 2 ) . The selections of kale by the small larvae bred on nasturtium were 15% as compared with 55% for a comparable size bred on kale. The selections of kale by the large larvae bred on nasturtium were 22% compared with 80% for a comparable size bred on kale. The greatest shift in food plant selections for the nasturtium-bred small larvae was 49% to mustard as compared with 25%, 9% to nasturtium as compared with 0%, and 16% with no selection as compared with 0%. For the large larvae, comparable data were 34% to mustard as compared with 20%, 33% to nasturtium as compared

with 0%, and 9% with no selection as compared with 0%. CONCLUSIONS:

( 1 ) The shifts in food-plant-selection by the larvae grown on different plants are highly significant and indicate a direct relationship between the feeding habits of the larvae, and their selection when given a free choice.

(2) The direct relationship between the size (and age) of the larvae and their selection of the plant previously eaten is clearly indicated.

(3) A plant previously of nearly negligible selection may be the most highly selected if the larvae have been grown on that plant. For example, larvae selected nasturtium over all others (33%) after being bred on that plant (Table 3), whereas larvae bred previously on kale had almost no selectivity for that plant.

INFLUENCE OF PREVIOUS FOOD PLANTS OF LARVAE

Additional experiments to test the influence of previous exposure to larval food plants are reported on here.

The first comparative test involves two strains of Pieris rapae, one from a population growing in the wild on black mustard and the other growing on cabbage. These strains were kept in the laboratory for several generations; the mustard strain was bred for over six genera- tions on mustard in the laboratory and the kale strain was bred on kale in the laboratory for over ten generations.

Larvae were selected for these experiments which had a size of 14 to 16 mm. Using twenty-five larvae of each strain, 600 tests of selection were made (Table 4) : the selected plants were mustard, kale, nasturtium, Isomeris and Cleome.

The only significant differences detected in the tests between the two strains were the relative selections made of mustard and kale. Larvae from the mustard-bred strain selected mustard 61% of the time compared with the kale-bred strains of larvae of 24% on that plant. On the other hand, kale was selected by the mustard-bred larvae 20%

TABLE 3. Choice of fi¥e kinds of plants by different sized larvae of Pieris rapae ( Series 2 )

57

1^62

THREE FACTORS

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58

HOVANITZ AND CHANG

/. Res. Lepid.

of. the time as compared with 59% by the kale-bred larvae. Testing these differences by chi-square using the four-fold table indicates a probability of less than 1 /million that the differences could be due to chance alone. This may be calculated in another way, that is, by taking 364 + 354 = 718 for one value and 119 + 144 = 263 for the other. The expectation that these differences might be due to chance alone, that is, that the deviations 718 — 981, and 971 — 263 are not due to

2 2 ‘ chance is well over one in a million.

CONCLUSIONS:

( 1 ) The shift in selection of mustard or of kale according to whether or not the larvae were from a kale or mustard strain is indicated by the experiments. The data are highly significant at an incredibly high level.

( 2 ) There is no significant change indicated in the selective level of the other plants involved as to whether or not the larvae were from the mustard or kale strain.

The second series of data on the problem of food plant selections involves nasturtium-bred larvae from a nasturtium strain and kale- bred larvae from a cabbage strain (Table 5). The experiments were carried out as before, two larvae of each strain were used, the same size for a total of forty trials each, of which ten were in each position as indicated in Figure 1.

The differences between the plant selections are again highly significant. The nasturtium -bred larvae as compared with the kale- bred larvae preferred mustard (35% as compared with 22.5%) and nasturtium (15% over 4%). The kale-bred larvae preferred kale (49% over 12.5%) and radish (22.5% over 14.0%). Neither selected Isomeris to any extent. A high proportion (22%) of the nasturtium-bred larvae rejected all plants.

CONCLUSIONS:

( 1 ) As in previous experiments, there was a shift in selection by the larvae according to the previous larval food plants.

( 2 ) This shift in selection was in the direction of the plant they had previously fed on. For example, nasturtium-bred larvae selected nasturtium better than did kale-bred larvae.

( 3 ) Even though nasturtium-bred larvae selected nasturtium better than did kale-bred larvae, mustard was preferred over nasturtium and over kale.

(4) The greater selection of mustard over kale bv nasturtium- bred larvae is significant not only in this experiment but also in a previously indicated test (Table 3). In both cases, kale is poorly preferred as compared with mustard when the larvae were nasturtium- bred.

(5) Radish is of lower selective influence when the larvae are

(i):5i-6i, 1962

THREE FACTORS

59

nasturtium-bred than when they are kale-bred. This was indicated also in previous tests ( Tables 3 and 1 ) .

(6) A significantly higher percentage of rejects (22%) are made by the nasturtium-bred larvae than by the kale-bred. This was also indicated in previous tests (Table 3 as compared with 1, 2 or 4).

DISCUSSION

All three factors, investigated as to their relevance in influencing larval choice of food, have been shown to be important in that regard. These factors are:

( 1 ) Influence of air movemenr.

(2) Influence of age (size) of larvae.

(3) Influence of food previously eaten by larvae, or strain of larvae.

In addition, by virtue of the laboratory set-up used in these experiments, some further conclusions may be drawn which are not completely in accord with some previous conclusions reached by others. One of these further conclusions is with regard to the ability of lepidopterous larvae to "recognize” food plants from a distance. In the present experiments, the larvae were attracted to the plants from a distance of over 120 mm without any difficulty and responded in most cases immediately.

Chin (1950) reports that the larvae of the Colorado potato beetle (Leptinotofsa) could not perceive its food plant from a distance farther than 2mm. Gupta and Thorsteinson (I960) tested the olfactory response of the larvae of the diamond backed moth [Plutella macul- ipennis (Curt.)] toward mustard oil odors and found that 5 mm was the maximum distance of response. Dethier (1959) in a study on food plant distribution and density and larval dispersal as factors affecting insect populations, states in relation to field observations that "Larvae find new food-plants by chance alone.” It is presumed that he had reference to the gross search for new food plants, not the closer relationship. In the case of the experiments of Chin, and Gupta and Thorsteinson, the screen test was used. In this, the larvae were placed on a screen above the food plant or other attractive source. In the present experiments, the larvae were below the food plants. This difference could account for a fundamental difference when testing for an odiferous substance heavier than air. Under natural conditions, our observations have always indicated that larvae tend to climb upwards rather than down so that tests involving simulated natural conditions should be best performed with the attraction above rather than below the larvae (Fig. 3). This point will be covered more fully in tests to be described in later papers.

In a paper available to us after the tests here indicated were performed, (Takata, 1959), there has been indicated a change in food plant preference of larva when reared successively on different food

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3. Larva of Pieris rapae on edge of pot during one of the selection experiments reaching out to black mustard plant three to four inches away. The larva had already traveled several inches under directed impulse to get this far.

plants for several generations. These results complement ours, even though the technique of testing used by Takata was different. He used cabbage and radish with Pieris rapae crucivora larvae. In testing, he used actual feeding experiments of the weight of leaves of the plants eaten by the larvae.

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61

SUMMARY

The evidence in this paper indicates ( 1 ) that larvae of Pieris rapae are capable’ of detecting their preferred food plant from a distance of at least 120 mm under the conditions of these experiments, (2) that the direction of wind movement is very important to detection of food plant, presumably through odor, (3) that the older and larger larvae are much better at selecting the preferred food plant at least at a distance and (4) that the influence of food previously eaten by the larvae, or the strain of the larvae, directly influences their choice of food in the direction of the previously eaten food.

LITERATURE CITED

CHIN, CHUN-TEH. 1950. Studies on the physiological relations between the larvae of Leptinotarsa decemlineata Say and some solanaceous plants. H. Veenman and Sons, Wageningen, Holland, pp. 1-88.

DETHIER, V. G. 1959. Food plant distribution and density and larval dispersal as factors affecting insect populations. Canad. Entom. 91: 581-596.

GUPTA, P. D. AND A. J. THORSTEINSON. I960. Food plant relation- ships of the diamond-backed moth (Plutella maculipennis (Curt.)). I. Gustation and olfaction in relation to botanical specificity of the larva. Ent. exp. and appl. 3 (I960) :24l-250.

TAKATA, N. 1959. Studies on the hobt preference of common cabbage butterfly, Pieris rapae crucivora (Boisduval). VI. Change in the food preference of larvae when reared successively by the definite food plant for several generations (preliminary report). Jap. J. Ecol. 9:224-227.

1(1) :63-71, 1962

Journal of Research on the Lepidoptera

THE GENERIC, SPECIFIC AND LOWER CATEGORY NAMES OF THE NEARCTIC BUTTERFLIES

PART 1 — The Genus Pieris

PADDY McHENRY

1032 E. Santa Anita, Burbank, California

PREFACE

INTRODUCTION

The author has asked that I write a brief introduction to this, the first of a series of compilations of generic, species and lower category names of the Nearctic butterflies. The objects of the work are (1) to give a complete list of all the names proposed for the butterflies of the Nearctic region from the year 1738 until the date of publication of the list, (2) to indicate the date and place where originally published, (3) to indicate the types of the genera, species and lower category names where known, (4) to indicate the type locality in the original author’s words for types, except those for the generic names, and (3) to indicate the location where types have been deposited where indicated by the author.

The biological application of these names so indicated is not to be attempted in this series. Instead, this effort is left to the individual who makes a comprehensive study of the biology of the groups con- cerned, such a person rarely having the time and inclination to make the detailed and laborious studies of nomenclature as such. There is urgent need for a work such as this even in a field as well civilized as the Lepidoptera; in fact, this kind of work is so long overdo that the civilized state is rapidly reverting to chaos. Each new volume which appears from the press on this group of insects plows under well established names with no reason given to justify such destruction. A most valuable start in the direction of making reason out of chaos was started by Francis Hemming in his TThe Generic Names of the Holarctic Butterflies” published in 1934. This work is proceeding also in the sam.e direction.

When the various parts of this work are completed, it is expected to reissue the whole as a separate volume. Then, perhaps we can prevail upon Mr. McHenry to go on to a similar effort with the moths,

William Hovanitz

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Each entry for the generic names includes the following; the name, the author’s name, the most accurate determinable publication date, the bibliographical reference (including the volume or subvolume for the date indicated ) , the type species, the selection of the type species and the supporting data to justify the type indicated.

Each entry for the specific names includes the following; the name as originally given, the author’s name, the most accurate determinable publication date, the bibliographical reference, data on type locality, sex, season, etc., other spellings of the name and notations of any homonym.

The date of publication of a name is indicated in a manner that shows its relative accuracy; for example, "mailing” and "release” dates if known are given preference over "publication” dates if they are not the same. All dates are given in English and normally in the sequence of day, month and year. Where more than one date is indicated, the more accurate one is given after the less accurate one. Dates ascertained directly from a source whose purpose was the determination of time of publication of a work are given without brackets; others, ascertained less directly are given in brackets and explained in a footnote. Combinations of dates with and without brackets may be given when necessary.

I have seen originals or photostats of all references except as noted but have been unable to ascertain the contents and dates for the various parts of Verity’s Rhopalocera Palaearctica.

The names of the genus Pieris are listed under the five species indicated, since in this genus the separation does not involve great difficulty. I have been aided in this regard by William Hovanitz, or by reference to the original description. Should these be in error, no harm is done since the total list, not the biological interpretation of the categories to which the names applied, is the purpose of the listing.

Should anyone find names which have been inadvertently omitted from this listing, a great service will be rendered to so notify the author or the editor of this fact so that corrections may be made.

I take this opportunity to express my gratitude for the use of facilities and to the staffs at the Allan Hancock Foundation Library of the University of Southern California, and at the Los Angeles County Museum Library & Entomological Department. A debt of gratitude is tenderd to the photographic service sections of the U. S. Department of Agriculture Library, Harvard College Library, New York Public Library, University of California Library and Cornell University Library. An extended exchange of correspondence with Mr. C. F. DosPassos has been most helpful.

LIST OF GENERIC NAMES USED OR AVAILABLE FOR PIERIS

ASCIA Scopoli.

Type; monuste L.

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65

MANCIPIUM Hubner.

Type: hellica Hubner = hellica L. = helice L.

PIERIS Schrank.

Type: hrassicae of var. authors = brassicae L.

ANDROPODUM Hubner.

Type: brassicae Hubner = brassicae L.

GANORIS Dalman.

Type: brassicae L.

TACHYPTERA Berge

Type: brassicae L.

PONTIA Fabricius.

Type: daplidice Fab. = daplidice L.

SYNCHLOE Hubner.

Type: callidice Butler = callidice Esper = callidice Hubner

ASCIA SCOPOLI. 1777. Introd. Hist. Natur. : 434, no. 175. Includes among others no. 80 (="P. D. [C.] monuste” of Linnaeus, 1767) which in turn is Papilio D. C. monuste Linnaeus, 1764.

Type Papilio D\anaus\ C[andidus]. monuste Linnaeus. 1764. Museum Ludovicae Ulricae ([I]) : 237, no. 56.

Type Selection. Scudder. 1872 [in or pre-June] L Syst. Rev. Some Amer. Butt., p. 40. Says of Ascia: "Type Papilio monuste Linn.”

MANCIPIUM HUBNER. [1 Jan. 1807] - [19 Dec. 1807]L Samrn. Exot.

Schmett, 1: pi. [141], ff. 1-4. Gives "Mancipium vorax hellica”. As used by Hubner, hellica is considered to be hellica Linnaeus, 1767 which in turn is helice Linnaeus, 1764.

Type. Papilio D[anaus]. C[andidus]. helice Linnaeus. 1764. Museum Ludovicae Ulricae ([I]) : p. 243, no. 62.

Type Selection. Hubner. As above. Gives only hellica, at the time, which becomes the type.

PIERIS SCHRANK. 1801. Fauna Boica 2(1): 152, no. 198; 2(1):

160-170, nos. 1283-1296. Includes Pieris brassicae which he says is Papilio brassicae of Goeze, Borkhausen, Brahm, and Esper. Of these authors, brassicae is considered to be hrassicae Linnaeus, 1758.

Type. P\ap)ilio\ D\anaus\ [Candidas] hrasicae Linnaeus. 1758. Syst.

Nat. 10th Ed. 467-468, no. 58.

Type Selection. Latreille. 1810. Consid. Gen. Anim. Crust. Arach. Ins. p. 440. Says: "Pieride. Pontia brassicae, Pab.”. As used by Latreille, brassicae Fabricius !s considered to be brassicae Linnaeus, 1758.

ANDROPODUM HUBNER. 1822. [post 22 Sept.]." Syst.-Alph. Verz. pp.

2-5, 7-9. Includes "Brassicae L, 401-403. Andropodum vorax.”

Type. P\apilio\ D[anaus]. [Candidas] hrassicae Linnaeus. 1758. Syst. Nat. 10th. Ed. 1:467-468, no. 58.

Type Selection. Hemming. Sept. 1933. Entomologist: 66(844) : 199. Says of Andropodum: "Type =: Andropodum hrassicae Linn.”

GANORIS DALMAN. 1816. Kongl. Vetenskaps Academiens Handlingar 1816(1) : 61-62, no. 8; 1816(1) : 86-90, nos. 1-10; tablet 1, no. 8; tablet 2, no. 8. Includes G. brassicae in which he cites Linnaeus Fauna Sv., pp. [269] -[2701, no. [10351 (this is hrassicae Linnaeus, 1761, which is hrassicae Linnaeus, 1758).

Type. Plapilio]. D[anaus]. [Candidas] Brassicae Linnaeus. 1758. Syst. Nat. 10th Ed. 1:467-468, no. 58.

Type Selection. Dalman. As above. Says of Ganoris: "Generis Typus: Pap- hrassicae”.

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TACHYPTERA BERGE. 1842. Schmetteclingsbuch, p. 19, pp. 92-105. Not seen, given as per Hemming, 1934.

Type. P[apilid\, .Dlanaus\ [Candidus] brassicae Linnaeus. 1758. Syst. Nat. 10th. Ed. 1:467-468, no. 58.

Type Selection. Hemming. Feb. 1934. Entomologist: 67(849) :38. Says of Tachyptera: "Type Papilio brassicae Linn., 1758.”

PONTIA FABRICIUS. 1807. In Illiger. Magazin fur Insektenkunde. 6:

283, no. 23. Includes: ’Tap . , . Daplidice”. As used by Fabricius daplidice is considered to be daplidice Linnaeus, 1758.

Type. P[apilio]. D[anaus]. [Candidus] daplidice Linnaeus. 1758. Syst. Nat. 10th Ed. 1:468, No. 2.

Type Selection. Curtis. 1824. Brit. Entom. 1: pi. 48. Not seen, given as per Hemming, 1934.

SYNCHLOE HUBNER. 1818 [post 22 Dec.]^. Zutr. Samm. Exot. Schmett.

1st. 100 (text in 1): p. 26, under no. 76. (Synchloe autodice). Includes "S. callidice”. Refers to his earlier publication of this butterfly.

Type. Papilio callidice Hifbner. [24 Dec. 1799] - [13 Apr. 1800]^. Samm. Europ. Schmett. (Papiliones) : plate 81, figs. 408-409. Page 63, no. 5 and plate 108, figs. 551-552 were published later.

Type Selection. Butler. 12 Sept. 1870. Cistula Ent. 1(3):51. Says of Synchloe: "Type S. callidice Esper”. As used by Butler callidice Esper is considered to be callidice Hubner [24 Dec. 1799] - [13 Apr. 1800].

LIST OF SPECIES AND LOWER CATEGORY NAMES USED OR AVAILABLE FOR PIERIS

1. P. (PONTIA) BECKERII EDWARDS. heckerii Edwards.

gzmderi Ingham. pseudochloridice McDimnough.

2. P. (PONTIA) SISYMBRII BOISDUVAL. elivata ( B. & B. ) .

jlava Edwards. flavitincta Comstock, J. A. sisymhrii Boisduval. transversa {B. 8iP>.)

3. P. (PONTIA) PROTODICE BOISDUVAL & LECONTE calyce Edwards. .

nastuftii Edwards ( Bdv. Ms. ) . nehoni Edwards. occidentalis Reakirt. protodice Boisduval & LeConte. vernalis Edwards.

4. P. (PIERIS) NAPI (LINNAEUS). acadica Edwards.

aestiva Edwards. arctica Verity. borealis Grote. casta Kirby.

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67

castoria Reakirt. cottlei Gunder. cruciferamm Boisduval. flava Edwards. flava Edwards. ffigida Scudder. hulda Edwards. hyemalis Edwards. iberides Boisduval. macdunnoughii Remington. marginalis Scudder. micro striata Comstock, J. A. mogollon Burdick. napi (Linnaeus). nasturtii Boisduval. ochsnheimeri Staudinger. oleracea Harris. pallida Scudder. pallidissima B. & McD. pseudobryoniae Verity. pseudoleracea Verity. pseudonapi B. & McD. resedae Boisduval. venosa Scudder. virginiensis Edwards. 1870. virginiensis Edwards. 1881.

5. P. (PIERIS) RAPAE (LINNAEUS). aestivus Verity.

immaculata De Selys-Longchamps. immaculata Cockerell. immaculata Skinner & Aaron. metra Stephens. novangliae Scudder. rapae ( Linnaeus ) . yreka Reakirt.

1. PIERIS (PONTIA) BECKERII EDWARDS.

heckerii Pieris Edwards. [Sept. 1871]*^. Butt. N. Amer. 1(8) : [28a] -

[29]; plate [81], figs. 4-7. 'cf described. "Virginia City, Nevada,

April 1870.” "Four individuals”. McDunnough, 1 Dec. 1928, spells heckeri.

gunderi, Ascia heckerii Ingham. 14 Apr. 1933. Pan-Pacific Ent. 9(2) :75. Holotype ? : "Bouquet Canyon, Los Angeles County, Calif”. "Bred from larva”, "emergence date June 21, 1932”. Type deposited: Calif. Acad. Sci., San Francisco, Calif.

pseudochloridice, Pieris heckeri McDunnough. 1 Dec. 1928. Can. Ent. 60(11) : 266-267. Holotype d* : "Oliver, B[ritish]. C[olumbia]., April 24 . . . No. 2861 in the Can. Nat. Coll., Ottawa”. Allotype ? : "Oliver,

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B.C., April 22”. Paratypes — I d*: "Hedley, B. C., May 15”. 1 9: "Osoyoos, B.C.” 1 + : "Osoyoos, B.C.”

2. PIERIS (PONTIA) SISYMBRII BOISDUVAL.

elivata, Ascia sisymhni Barnes & Benjamin. 8 Dec. 1926. Bull. Sou. Calif. Acad. Sci. 25(3) :88, no. 33a. "Type locality: Glenwood Springs, Colo.”. "Number and sexes of types: Holotype d* May 1895, Allotype ? May 1895, 7 d» 14 9 Paratypes, various dates April to June”.

jlava, Pieris sisymhri Edwards. Apr. 1883. Butt. N. Amer. 2(11): [67];

plate [151. fig 5. ? described. No locality, series data nor dates given. flavitincta, Pieris sisymhrii Comstock, J. A. 20 Feb. 1924. Bull. Sou. Calif. Acad. Sci. 23(1) : 19-20; plate 7, fig. 9. 9 described. "The example before us was captured . . . April 30th, 1911 at Cranbrook, British Columbia”. Intends to propose new name for jlava Edwards. sisymhrii, Pieris Boisduval. 1852 [25 Feb. - 22 Dec. Ann. Soc. Ent. France. 2nd Ser. 10 (2) :284, no. 8. 9 described. [California]. No series data nor dates given. Edwards, Apr. 1883, spells sisymhri. transversa, Ascia sisymhrii Barnes & Benjamin. 8 Dec. 1926. Bull. Sou. Calif. Acad. Sci. 25(3): 88, under no. 33. "Type localities: Paradise, Cochise Co., Ariz.; Redington, Ariz.”. "Number and sexes of types: Holotype cf , Allotype 9,1 9 Paratype, all March; 1 cf Paratype, no date”.

3. PIERIS (PONTIA) PROTODICE BOISDUVAL & LECONTE.

calyce, Pieris Edwards. Nov. 1870. Trans. Amer. Ent. Soc. 3(?) sign. 25: 189, no. 1 (Nomen nudum); 189. d* described. "From Nevada; in the collection of Henry Edwards”. No series data nor dates given. nasturtii, Pieris Edwards (Boisduval Ms. name). [9 May 1864]°. Proc. Ent. Soc. Phila. 2(4) : 501, no. 1 (Nomen nudum); 501. d* & 9 described. "San Francisco; from Dr. Behr, who informs me that it is common in some localities in the vicinity of that city”. No series data nor dates given.

nelsoni, Pieris Edwards. Apr. 1883 Butt. N. Amer. 2(11): [71] - [72];

plate [15], figs. 6-7. "1 cf ... St. Michael’s Alaska, June, 1881”. occidentalis, Pieris Reakirt. June 1866. Proc. Ent. Soc. Phila. 6 (pp. 121-152) : 133-134. cf & 9 described. "Hab. - Rocky Mountains, Colorado Territory, California, (Coll. Tryon Reakirt)”. No series data nor dates given.

protodice, P[ieris]. Boisduval & LeConte. 1829. Hist. Gen. Icon. Lepid- Chen. I’Amer. Sept. 1 (5) :45-46. Plate 17, figs. 1-3 published later. A & 9 described. "Elle parait au printemps et a la fin de juin aux

environs de New-York. Nous en avons vu un individu pris dans le

Connecticut”.

vernalis. Pieris Edwards. [9 May 1864]®. Proc. Ent. Soc. Phila. 2(4) : 501, no. 2 (Nomen nudum); 2 (4) :501-502. cf & 9 described. "In the collection of Mr. Geo. Newman and Mr. Wilt are several specimens, taken, as I am informed, at Red Bank, New Jersey, in the month of May”. "There is also in the Society’s collection a pair from the Rocky Mountains, that appear to be identical with it”.

4. PIERIS (PIERIS) NAPI (LINNAEUS). _ .

acadica, Pieris napi Edwards. June 1881. Papilio l(6):86-88 (in pt.),

sub no. 1; p. 98, no. 1 of no. 3; p. 99; plate 3, figs. 10-11. It appears that one pair was from Southern Newfoundland and was taken in the

last week in July, it also appears another set ( 1 cf 2 9 ) had emerged

from pupae in August and was from the same locality. aestiva, Pieris napi oleracea Edwards. June 1881. Papilio l(6):86-88 (in pt.. Nomen nudum), sub no. 1; l(6):89-95 (in pt.)

sub no. 3; l(6):95-98 (in pt.), sub no. 4; 1(6):98, no. 3 of no. 3;

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NAMES — Pt. 1

69

1(6):99; plate 3, figs. 15-16. cf & described. "NewYork” (see figs, explanation, p, 99). "summer brood”. No series data given. arcUca, Pieris napi frigida Verity. 1905-1911. Rhopal. Palaearctica : pp. 333-334 (in pt., cites figs 32-33 on plate XXXII and figs. 16-17 on plate LXVII as P. n. f. arctica)\ plate XXXII, figs. 32-33; plate XXXII explanation page, figs. 32-33 (gives as P. n. frigida); plate LXVII, figs. 16-17; plate LXVII explanation page, figs. 16-17 (gives as P. n. arctica); p. xxviii (cites figs. 31-33 & 36-37 on plate XXXII and figs. 16-17 on plate LXVII, gives as P. n. /. arctica). "31 . . . cf (ile d’Yesso, Japon)”. "32 . . . c? , (Norvege sept.)”. "33 . . . d* (Nulato, Alaska)”. "36 ... $ (Nulato, Alaska)”. "37 ... 9 .(Finmark, Scandinavie) ”. ”16 , 9 (Saltdalen, Norvege sept.) ”. "17

. . . ? (Laponie)”. Figs. 31, 33, 36: [coll, de Joannis]. Fig. 32: [coll. Stefanelli]. Fig. 37: [coll. Obth.] Fig. 16: le coll. Mourray]. Fig. 17: [e coll. Leach]. No series data nor dates given. borealis, Ganoris oleracea Grote. Nov. 1873. Bull. Buffalo Soc. Nat. Sci. 1(4) sign. 24:185. "months of June and July, on the Island of Anti- costi”. No series data nor sex given.

casta, Pontia Kirby, W. 1837. In J. Richardson. Fauna Boreali-America (4) :288, no. 1; plate 3, fig. 1. "Three specimens taken in Lat. 65°”. No sex given.

castoria, Pieris Reakirt. [11 June 1866] - [13 Feb. 1867]*^. Proc. Acad. Nat. Sci. Phila. [18] (3) :238, no. 2. d* described. "Hab. - California. Coll. Tryon Reakirt”. No series data nor dates given. cottlei, Pieris napi castoria Gunder. 6 July 1925. Ent. ^ews 36(7) :197- 198, no. 9; plate 5, fig. 9; Holotype d : "(author’s Coll.), Anderson Springs, Lake County, California, May 5, 1919”. crucifer arum, Pieris Boisduval. 1836 [in or post Apr.]^°. Hist. Nat. Ins. Spec. Gen Lepid. 1 (text in 1) :519, no. 119. d* described, "dans les provinces septentrionale des Etats-Unis”. No series data nor dates given. flava, Pieris napi pallida Edwards. June 1881. Papilio 1(6) :89”95 (in pt., unnamed), sub no. 3; 98, sub no, 2 of no. 3. "Washington Terr[itory].”. "One of these [a $ ] is yellow on the upper side”. No date given. flava, Pieris napi venosa Edwards. June 1881. Papilio 1(6) :88-89 (in pt,, unnamed), sub no. 2; 98, sub no. 1 of no. 2. Fig. 7 of plate 2 (although not so named in plate explanation, p. 99) appears to be flava. "A large percentage of female Venosa are yellow on the upper side”. No locality, series data nor dates given. frigida, Pieris Scudder. Sept. 1861. Proc. Boston Soc. Nat. Hist. (8(?) sign. 12:181-182. "Two . . . males . . . two females”, "on Caribou Island, Straits of Belle Isle”. No dates given. hulda, Pieris Edwards. Sept. 1869. Trans. Amer. Ent. Soc. 2(?) sign.

48:370. "From Kodiak, 1 o* . Coll, of Henry Edwards”, No date given. hyemalis, Pieris napi oleracea Edwards. June 1881. Papilio l(6):88-89 (in pt.. Nomen nudum), sub no. 2; 89-95 (in pt.), sub no. 3; 95-98 (in pt.), sub no. 4; 99; plate 2, fig. 8. d* &■ $ described. Directly and indirealy cites material from New Hampshire, Massachusetts, Lake Superior area and Mt. Hood, Oregon. No series data nor dates given. iherides, Pieris Boisduval. [1869, pre 1 Nov.]^’. Ann. Soc. Ent. Belgique 12 (in 1):39, no. 9. d* & ? described. [California]. No series data nor dates given.

macdunnoughii, Pieris napi Remington. 17 Sept. 1954. The Lepid News 8(3-4) :75. A new name for Pieris napi pseudonapi Barnes & McDun- nough, 5 Dec. 1916. See pseudonapi for series data. marginalis, Pieris Scudder. Stpt, I86I. Proc. Boston Soc. Nat. Hist. 8(?) sign. 12:183. "(Id* ,1 9 ) which are in the Museum of Comparative Zoology”. The male . . . from Gulf of Georgia, and the female from Crescent City, California”. No dates given.

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/. Re$. Lepid.

mkrostfiata, Pieris napi Comstock, J. A. 12 Sept. 1924. Bull. Sou. Calif. Acad. Sci. 23(4) :125. Holotype f:- "Eldredge, Sonoma County, Cali- fornia. March 13, 1911”. Allotype [•$■]: “same locality and on the same date”. 'Taratype; one male - same locality and date”.

mogollon, Pieris napi Burdick. 28 Sept. 1942. Can, Ent. 74 (8) :154-155. Holotype : "Mogollon Range, Catron Co., New Mexico, 5»7-40. No. 5222 in the Can . . . Nat . , . Coll . . . , Ottawa”. Allotype $ : "same data”. "Paratypes. 2 ^ ,same data; 3 cf , Sierra Blanca, Lincoln Co., N. M., 5-25-40; all in the Can , . . Nat . . . Coll . . . , Ottawa. 1 d* , Mogollon Range, Catron Co., N. M., 5-7-40 and 1 $ , Sierra Blanca Range, Lincoln Co., N. M., 5-20-40; in the U , . . S . . .^at . . . Mus . . Fifty-six paratypes from the above locations in the collection of the author, from which other museums will be supplied”.

napi, P[apilio]. Dlanausl. [Candidus] Linnaeus. 1758. Syst. Nat. 10th. Ed. 1 ;468, no, 60. No locality, series data, sex nor dates given. Edwards, June 1881, spells napae.

nasturtii, Pieris Boisduval. [1869, pre 1 Nov.]^L Ann. Soc. Ent. Belgique (12) (in 1) :38-39, no. 7. described, "dans les champs decouverts au pied de la Juba”. "Nous o’avons vu que des males”. No series data dates given. A homonym of Pieris nasturtii Edwards, [9 May 1864].

ochsenheimeri, Pieris Staudioger. End Apr. 1886. Ent. Zeitung Stettin 47 (4-6) : 199-200. d & 9 described, "wo sie die beiden Haberhauer in Anzahl Ende Juni bei Namagao, jedenfalls hoch in den Gebirgen ge fangen batten. Auch Maurer sandte mir in demselben Jahre ein im Alai-Gebirge (sudlich von Margelan) gefangeoes + ein”. No series data given.

oleracea, Pontia Har^fs. 10 July 1829. The New England Farmer & Horti- cultural Jour. 7(51) :402. "Habitat ... in New Hampshire, and Massa- chusetts”. No series data nor sex given, "two broods in a season”: [May- June - August].

pallida, Pieris Scudder. Sept. 1861. Proc. Boston Soc. Nat. Hist. 8 (?) sign. 12:183. "five specimens (3 d* » 2 9.), which are in the Museum of Comparative Zoology”. "Gulf of Georgia”. No dates given.

pallidissima, Pieris napi Barnes & McDunnough. 5 Dec. 1916. Contrib. Nat. Hist. Lepid N. Amer. 3(2) :59; 142; plate 6, figs. 4-5 & 10. "second generation (July, August)”, "type cf and $ from Provo, Utah”. No series data given.

pseudobryoniae, Pieris napi frigida Verity. 1905-1911. Rhopal.- Palaearctica : p. 146 (cites figs. 46-37 on plate XXXII, gives as P. n. f. pseudo- bryoniae); plate XXXII, figs. 36-37; plate XXXII explanation page, figs. 36-37 (gives as P. n. frigida); p. xxviii (cites only fig. 37, gives as P. n. f. arctica pseudobryoniae) . "36 ... 9 (Nulato, Alaska) [coll, de Joannis]”. "37 . . (Finmark, Scandiriavie) [coll. Obth.]”. No series data nor dates given.

pseudoleracea, Pieris napi frigida Verity. 1905-1911. Rhopal. Palaearaica: p. 146; plate XXII, fig. 38; plate XXXII explanation page, fig. 38; p. xxviii. "38 . . . d' (Labrador) [e- coll. Boisduval in coll, obth.]”. No series data nor dates given.

pseudonapi, Pieris napi Barnes & McDunnough. 5 Dec. 1916. Contrib. Nat. Hist. Lepid. N. Amer. 3(2) :57; 142; plate 6, figs. 1-3. "type ^ and 9 taken at Silverton, Colo ... in the last week of July”. No series data given. A. homonym of Pieris melete pseudonapi Verity, 1905-1911.

resedae, Pieris Boisduval. [1869, pre 1 Nov.]^ ’ Ann. Soc. Ent. Belgique 12 (in 1) :38-39, no. 8. 9 described. "Nous ne connaissons cette espece que par un seul individu 'femelle pris . . . sur les bords du Sacramento”. No date given.

venosa, Pieris Scudder. Sept. 1861. Proc. Boston Soc. Nat. Hist. 8(?)

i(i):6}-ji, 1^62

NAMES — Pt. 1

71

sign. 12:182-183. "twenty specimens (5 cf , 15 9 ), brought to the Museum of Comparative Zoology, from San Mateo and Mendocino city, California”. No dates given.

vkginiensis, Pieris Edwards. Jan. 1870. Trans. Amer. Ent. Soc. 3(?) sign. 2:10, no. 5 (Nomen nudum); 13-14. cf & $ described. "Not uncom- mon in the Kanawha district [West Virginia] in the month of May, and there replacing Oleracea. I have received from Mr. Saunders occasionally specimens taken by him at London, Canada”. No series data given. virginiensis, Pieris napi oleracea hyemalis Edwards. June 1881. Papilio 1 (6) :95-98 (in pt.), sub no. 4; 98, under no. 2 of no. 2. " . . . Virgin- iensis . . . has become a true species, although unquestionably, in a higher latitude, it appears as an occasional aberration only of Oleracea". Speci- men data is obscure. A homonym of virginiensis Edwards, Jan. 1870.

5. PIERIS (PIERIS) RAPAE (LINNAEUS).

aestivus, Pieris rapae Verity. 16 May 1913. Jour. Linn. Soc. (London), Zool. 32 (215) :177-178. "summer brood”. No locality nor series data given.

immaculatag Pieris rapae De Selys-Longchamps. 1857. Ann. Soc. Ent. Belgique 1 (in 1) :5, under no. 5. [Belgique]. No series data, sex nor dates given.

immaculata, Pieris rapae Cockerell. Apr. 1889. Entomologist: 22(311) :99. No locality, series data, sex nor dates given. Cites p. I6l in Newman’s Brit. Butt. A homonym of Pieris napi immaculata De Selys-Longchamps, 1857.

immaculata, Pieris rapae Skinner & Aaron. 2 July 1889. Can. Ent. 21(7) : 128-129. "five specimens in the collection of Am. Ent. Soc., Dr. Skin- ner and E. M. Aaron”. No sex nor dates given. A homonym of Pieris rapae immaculata De Selys-Longchamps, 1857 and Cockerell, Apr. 1889. metra, Pontia Stephens. 1 Aug. 1827. Illust. Brit. Ent. 1(?) sign, d: 19-20, no. 4:146-147 published later, cf & ? described. "The insect occurs early in April and a second time towards the end of June. I obtained specimens of the first brood at Hertford; and of the second I captured some this season, at Ripley at the latter period”. novangliae, Ganoris rapae Scudder. Apr. 1872. Can. Ent. 4(4) :79. "Two of my specimens were taken in June and July, 1869 — - one ... in Shelbourne, N[ew]. H[ampshire] . . . the other ... in Waterville, M[aine]., and all are males”.

rapae, P[apilio]. D\anaus\ [Candidusi Linnaeus. 1758. Syst. Nat. 10th. Ed.

l(in 1):468, no. 59. No locality, series data, sex nor dates given, yreka, Pieris Reakirt. [11 June 1866] - [13 Feb. 1867]'^. Proc. Acad. Nat. Sci. Phila. [18](3):238, no. 1. cf & 9 described. "Hab. - California. Coll. Tryon Reakirt”. No series data nor dates given.

lAmer. Nat. 6: 3S4-559. Work is reviewed in June 1872 number.

^Hemming, 1937. Hubner 1:327-437.

^The work title page signature date qualified by preface signature date on page vi.

•^Title page signature date qualified by preface signature on page 6.

■^Hemming. 1937. Hubner. 1:146-324.

^Hemming. 1931. Proc. Ent. Soc. London. Ser. A. 6: 42-45. Gives actual dates of publication for the parts of Edwards’s Butt. N. Amer., (Ser. I).

7Tome 10 title page signature date qualified by the meeting date of 25 Feb. (p. 275) and the evidence indicating that the tome to page 489 was published before the meeting of 22 Dec. (p. Ixxxii in Bulletin).

SProc. Ent. Soc. Phila. 1864. 3: p. 695. Notes that No. 4 of Vol. 2 of Proc. Ent. Soc. Phila. was received at 9 May 1864 meeting.

9lndex Scient. Cont. Jour. & Proc. Acad. Nat. Sci. Phila., 1812-1912: pp. xii-xiii. Gives dates of receipt for various parts of the early volume of the Proceedings.

1 OTome I title page signature date qualified by preface date (p. xii).

' 1 Trans. Ent. Soc. London 1869; p. xix (in Proc.). Notes receipt of Tomes 1-12 of the Ann. Soc. Ent. Belg. at 1 Nov. meeting. Tome 12 title page signature date: 1868-1869. I assume the date is fixed on the publication of Tome 12, I have no data for the separate except that its title page signature date is 1869.

Journal of Research on the Lepidoptera 1(1) :73-83, 1962

1140 W. Orange Grove Ave., Arcadia, California, U,S.A.

THE DISTRIBUTION OF THE SPECIES OF THE GENUS PIERIS IN NORTH AMERICA’

WILLIAM HOVANITZ = ’

1140 ]F. Orange Grove Ave., Arcadia, Calif.

The North American species of the Genus Pieris are distributed from the Arctic Ocean to Guatemala. However, none of the species of the genus (sensu stricto) exist in habitats which would be con- sidered as tundra or arctic-alpine on the one hand, or as wholly tropical on the other. To this extent, the genus compares somewhat with Colias; the latter, however, contains two species that do exist in the tundra habitat.

The concept of a species which has been applied here is the same as that which has been applied previously to the species of the genus Colias in drawing the distribution maps for that genus (Hovanitz, 1950). This concept is based upon the consideration that the most important factor in stability of a species is the genetical population — or the interbreeding unit. Since, however, genes and their combinations cannot be seen, nor analyzed except by means of their effects on the appearance and physiology of the individuals carrying them, they must be studied through a comparative study of their morphological, anatom- ical or physiological characteristics. Thus, a name applied to one population may be applied to another population, or to many popula- tions, if their characteristics indicate that a similarity exists between the hereditary makeup of such different populations. Such a name may cover quite a diversity of differences in the same population, or even a diversity of different populations if they are genetically separated one from the other by geographical or ecological means. The extent of gene interchange as well as the evaluation of the isolation mechanism determines whether or not one population should be considered as the

’Aided by a grant from tbe National Science Foundation, Washington, D.C.

2The author wishes to thank the following for having made this distributional work possible by making available the collections under their care: C. B. MacNeil, California Academy of Sciences, San Francisco; L. M. Martin, Los Angeles County Museum, Los Angeles; T. N. Freeman, Entomological Research Institute, Ottawa; F. Rindge, American Mus'^um of Natural History, New York; Harry Clench, Carnegie Museum, Pittsburgh; W. S. Field and J. F. Gates Clark, U.S. National Museum, Washington, D.C.; and the Dept, of Entomology, Chicago Natural History Museum, Chicago, Illinois.

3The base maps used in this paper are from Goodes Series of Base Maps by the University of Chicago Press, used by permission.

73

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’same species” as another, or a "subspecies” or "geographical race” of. it, or should not be considered significantly different. These criteria will be more exhaustively dealt with in a later paper. For practicability, different criteria must be used at different times and in varying circum- stances. The ultimate taxonomic designation is a product of weighing a great number of problems, some factors being known and others unknown, with the hope that the best result may be achieved. Another general rule underlies these studies; namely, that stability and uni- formity are desirable in nomenclature, and that past taxonomic decisions should not be upset by hasty, poorly-thought-out changes. But the past should not remain immutable when the decision to change is demanded by sound study or experimental evidence. Implicit in all taxonomic studies is perhaps an amount of individual opinion, perhaps greater than in many more experimental sciences, but even this can be greatly reduced by conscious effort to separate fact from opinion. It is the belief of the author that all facts upon which decisions are based should be stated; these are the "data” which can be refuted. New decisions should be made then only upon presentations of new data. Taxonomy by "hunches” is to be avoided; decisions should be accompanied by evidences for and against any decisions made.

THE SPECIES OF PIERIS

There are five clearly defined species of Pieris in North America. Of these, only four were native prior to 1800. Besides these, there are two other groups of related populations which might be considered "species,” or sibling species, and a large number of geographical varia- tions within each of these species, many of which are distinctive enough to be called "geographical races” or subspecies. Division of the species into geographical races is not to be considered in this paper, with the exception of the two sibling species just mentioned.

Pieris rapae. This is one of two common European species of Pieris, the first immigrants* of which appear to have been introduced into North America prior to I860. Since that time, the species has spread over the whole of the Unitd States and much of Canada and Mexico, wherever the natural vegetation has been at least partially replaced by European weeds, such as black mustard, or by cruciferous agriculture. This species has a wide range of habitat which is suitable for its existence, since it is found from the warm parts of the Gulf of Mexico nearly to the tundra of Canada, and from the Imperial Valley below sea level to high mountain meadows in the Sierra Nevada or the Rocky Mountains. The food plants utilized are a variety of cruciferous plants, among which are all varieties of cruciferous garden vegetables (cabbage, kohlrabi, kale, etc.) as well as many weedy plants such as mustards, radish, sisymbrium, etc. Some garden flowers such as nasturtium are also utilized. In view of the "weedy” nature of this species, no map is given to illustrate its distribution.

i(i):73-S3, 1962

PIERIS DISTRIBUTION

75

Pieris napi (Fig. 1). This species is found throughout northern Europe and Asia where there is in effect a continuity with the forms of North America across the Bering straits and the islands of the Bering Sea, This is the most northern of all of the species of Pieris, its range extending to the edge of the tundra or slightly beyond along its northern limits. The northern distributional limit from the Macken- zie River and east follows closely the northern limits of the tree line. The species exists along both the Pacific and Atlantic coast lines, but extends farther southward on the Pacific Coast than on the Atlantic Coast. The southern-most population on the immediate Pacific Coast line is at Lopez Canyon, San Luis Obispo County, California at about 35° north latitude. On the east coast at sea level, the most southern locality known is along the coast of New York and Connecticut opposite Long Island at 42° north latitude. However, at increasing elevations in the Appalachian Mountains southward, P. napi ( or P. vifginiensis) may be found as far south as the Great Smoky Mountains of Tennessee and North Carolina at about 35° north latitude. The southernmost extension of range of Pieris napi in the strict sense is in the vicinity of Connecticut and the Appalachians of Vermont, New Hampshire and Massachusetts. Westward, the range passes through the lower part of Ontario, Michigan, Wiconsin, Minne- sota, Manitoba, Saskatchewan and Alberta, always staying north of the prairies. A fuller discussion of the relation of Pieris napi to P. virginiensis is to be had in a separate paper to follow this one.

Where the range of P. napi reaches the Rocky Mountains in central Alberta, the species extends clear to the Pacific coast and southward in the Rocky Mountains at increasing elevations to southern New Mexico and Arizona. The species appears to be absent in the drier ranges of the Great Basin and northward in the sagebrush country into south-central British Columbia. Elsewhere, it is widely distributed in the habitats that it prefers, these being damp wooded areas with partial shade, and temperatures not over seventy degrees Fahrenheit..

Of interest in the search for extensions of range are the following specific locations on the southern parts of the range of Pieris napi:

California: Coast — - San Luis Obispo County, Lopez Canyon, December through May.

California: Western side Sierra Nevada, Merced County, Yosemite Valley, 3-4000 feet, April-May.

California: Eastern side Sierra Nevada, Placer County, 6-7000 feet, June.

Nevada: No records at present.

Arizona: Apache County, White Mountains, August; Gila County, "Globe” July.

New Mexico: Otero County, James Canyon, Cloudcroft, August, Catron 6, Mogollon, May, August.

Georgia: No records.

76

HOVANITZ

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FIGURE 1.

Map showing the North ndpi.

American distribution of Pieris (Pieris)

(i):73-^3, 1962

PIERIS DISTRIBUTION

77

South Carolina: No records.

North Carolina: Black Mountains, April.

Tennessee: Great Smoky National Park, Cherokee, April.

Some other points of interest in the distribution of this species are

the following records :

Pribilof Islands, Alaska, July. Mouth of the Mackenzie River, North West Territories.

Great Bear , Lake, N.W.T. Churchill, Manitoba ( Hudson Bay ) . James Bay, Hudson Bay, Quebec. Ramak, Labrador

Pieris napi is the only known butterfly to inhabit the Aleutian Island^ or the islands of the Bering Sea. This ability is probably correlated with its adaptation to existence at temperatures below 70 °F, with low solar radiation and high humidity.

Pieris (Pontia) protodice (Fig. 2). This is the most widely distributed species of Pieris in North America. Some prefer to place this species, together with the following two species, in a separate genus Pontia for which there is much to recommend. To do so, however, would reduce the size of the. genus Pieris beyond what would seem reasonable, and, therefore, to obviate this difficulty, and yet show phylogenetic relationship, Pontia would best be retained as a subgenus name.

Pieris protodice is best adapted to habitats with more sunshine than is required by P. napi. It also is enabled to survive in habitats much too warm for that species. However, cold does not seem to be a limiting factor as long as there is a short warm season and plenty of sunlight. These conditions, to some degree, pertain to the area occupied by the species. It apparently does not flourish in areas of continual hot temperatures as indicated by its absence in all fully tropical climates.

Pieris protodice differs from P. napi in its absence all along the immediate Pacific Coast from northern California through Alaska in keeping with its dislike for cool, cloudy areas. It is absent in the northern half of Alaska but eastward its distributional limits parallel those of the timbered area, as with P. napi. East of the Hudson Bay, however, P. protodice is absent north and east of Ottawa and New York State. The reasons for this event are baffling unless the present distribution of the species has been greatly disturbed by man in the eastern regions of North America as has been found true for Colias eurytheme. Pieris protodice prefers sunny, open fields as compared with P. napi which prefers partially shaded, damp areas. The cutting of the eastern deciduous forest to produce open fields for agriculture has aided both Colias eurytheme and Pieris protodice in extending their ranges and population density. It has probably a^so reduced the range and population density of Pieris napi since the habitats are conflicting. This probably accounts for the known diminution of Pieris napi in the region of Cambridge, Massachusetts where they were once exceed- ingy abundant, and now rare.

78

HOVANITZ

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FIGURE 2. Map showing the North American distribution of Pieris (Pontia) protodice.

(0!73-^3,

PIERIS DISTRIBUTION

79

Pieris protodice is found throughout the southeast from Long Island to the southern part of Florida and around the Gulf of Mexico to Guatemala. It is very abundant in the highlands of Mexico but may be found nearly everywhere except in woods or forested areas. It is found from the southern tip of Lower California northwards, having a great preference for open areas. It is possible that its great abundance in southern California coastal areas is a recent event, correlated with the change of the natural perennial grasslands to annual European grasses, mixed with Brassica nigra, the black mustard. It reaches its greatest abundance, however, in the desert regions where conditions of cool nights, hot days, full sunlight and periodic extensive abundance of food plants {Cleome, Brassica, Sisymbrium, etc.) allow the species to swarm in clouds. In such areas, the population abundance is usually limited by the periodicity of available water.

In the mountain areas, the species is spread from the lowest valleys to the top of the highest mountains. The author has collected Pieris protodice at the top of Mt. Whitney, 14,500 feet elevation, the highest point in the United States south of Alaska, and in the bottom of Death Valley and Imperial Valley below sea level.

The relationship of Pieris occidentalis to Pieris protodice is here left in doubt, but for the purposes of the map (Fig. 2), they are considered forms of one species. This point will be considered in more detail in a future paper. There is no doubt that at higher elevations and cooler temperatures, populations exist which have a blacker, fuller pattern on their wings than populations which exist at lower elevations at higher temperatures. The preponderance of the evidence suggests that these differences are not hereditarily controled, but that they are dependent entirely upon the environmental conditions. Within the species as a whole, as with P. napi, the darker indiyiduals exist in the more northern latitudes at cooler temperatures than the lighter ones. However, this relationship must be reconciled with local factors. In Colorado, Brown (1957) has shown that P. occidentalis appears to form definite populations at high elevations whereas P. protodice forms populations at low elevations. F. Rindge, however, in a personal com- munications has found both in considerable number in the same valley in Utah. These points cannot be reconciled at the present time. P. protodice when exposed to low temperatures develops a color pattern (more extensive melanin) which is similar to, or identical with, P, occidentalis. They could very likely be genetically the same and if they are genetically the same, they are not deserving of a scientific or Latin name of significance nomenclatorially. This point has not been proved, however. In the case of geographical variations, such deviations are considered subspecific unless proved otherwise. In the case of altitudinal or seasonal differences, such as in Pieris protodice or Colias eury theme, it is suggestd that Latin names not be applied except to geographically isolated populations and then in a subspecies sense only.

80

HOVANITZ

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FIGURE 3. Map showing the North American distribution of Pieris (Pontia) sisjmbrii.

(i):73-h> 1962

PIERIS DISTRIBUTION

81

Pieris (Pontia) sisymbrii. (Fig. 3) The Pontia subgenus of the Pierids all prefer dry habitats with considerable sunshine exposure, unlike Pieris napi or even Pieris rapae which prefer or can survive in shade and high humidity. Pieris sisymbrii is one of these. Its habitats are always open, highly exposed, usually rocky places. It prefers cool temperatures but with high solar radiation. It lives in the ’spring time in, the desert, as in the Mohave Desert where it flies at temperatures of highs not over 70° F, even though the temperatures later in the year will be over 100° F. It also lives in the mountains at elevations of over 10,000 feet in June and July. In the coastal area of California, its habitats are usually dry, rocky areas (serpentine, etc.) which are more dry and more exposed to solar radiation than its general position on the map would indicate.

Geographically (Fig. 3), the species exists throughout the moun- tainous areas of the west from the Yukon Territory to Mexico. It probably also exists in northern Mexico but there are no records. Outside of this area, there are a series of locations in the Northwest Territories from the Great Bear Lake southward past the Great Slave Lake to Lake Athabasca. Between these locations and the Rocky Mountains there are no locations known. This is probably due to lack of many suitable habitats. Collectors would do well to increase the known distribution of this species. It has a wide distribution but is characterized by the extreme isolated nature of them. Its habitats are narrowly restricted even on the desert and the adults have a short adult life, flying for only a few weeks during the year at any one place. The species aestivates and hibernates as a pupa which is very hard and impervious to water.

There is relatively little variation between the individuals in a population in this species, and also relatively little variation geographi- cally between populations. Some variations have been described, how- ever, and will be considered in a subsequent paper.

Pieris protodice is a species which is generally distributed and has many generations per year; it is therefore genetically and physiologi- cally pliable as is necessary to meet these changed conditions. On the other hand, Pieris sisymbrii is greatly restricted to isolated habitats, and the adults fly only a short time; thus, the species genetically may be said to have developed a narrower range of tolerance through a nar- rower range of selective factors of the environment.

Pieris (Pontia) heckerii. (Fig. 4). Of all the species of North American Pieris, P, heckerii has the most restricted geographical range, extending from south-central British Columbia east of the Cascade Mountains southwards east of the Sierra Nevada into the deserts of southern California (Fig. 4). Its eastward limits coincide with the Rocky Mountain system in Montana, Wyoming and Colorado. The species does not extend into New Mexico so far as is known, unlike Pieris sisymbrii. The most southern-known limits are southwestern

82

HOVANITZ

J. Res. tepid.

FIGURE 4. Map showing the North American distribution of Pieris (Pontia) beckerii.

(i):7}-Sl. 1962

PIERIS DISTRIBUTION

83

Colorado, central Arizona, and southern Nevada, except for California where the species may be found in the foothills of the mountain ranges especially on the desert side. However, the species has been found on the coastal side in the area of the Santa Susana Valley (Moorpark), San Fernando Valley, Santa Clara River Valley and on the immediate coast from San Diego and southwards.

Pieris heckerii exists at elevations of sea level at the coast and some parts of the desert to 9000 feet in the mountain valleys. It has always been found in areas that are relatively dry or desert-like with high solar radiation. Its distributional range coincides almost perfectly with that of the semi-arid brushlands extending from the rain-shadow valleys of central British Columbia, throughout the Great Basin and inter-moun- tain valleys of the Rocky Mountains. The factors that limit its distribu- tion in southern Arizona, New Mexico and northern Mexico are unknown. Perhaps there is a lack of proper food plant. The distribu- tion of the species in southern California south of the Great Basin is correlated closely with the distribution of Isomeris arhorea, its preferred food plant. It seems likely, however, that some other plant may also satisfy for this purpose. There is little doubt that intensive searching for additional poptilations of Pieris heckerii in the range of Isomeris will extend the distribution some considerable distance, especially in the south Coast Ranges of California, the foothills of the Sierra Nevada and southward in Baja California.

Unlike Pieris sisymhrii which has a single short generation per year, in southern California, Pieris heckerii has a succession of genera- tions with the bulk of the adult flight being correlated with the time of of the winter rains. However, in the mountainous regions north of the Mohave Desert, the species has only one known generation, in the early summer.

There is little geographical, local population, or seasonal variation in Pieris heckerii. However, some races have been described and will be considered in a later paper.

LITERATURE CITED

BROWN, F. M., D. EFF AND B. ROTGER. 1957. Colorado butterflies.

Proc. Denver Mus. Nat. Hist. Nos. 3-7:1-368.

HOVANITZ, WILLIAM. 1950. The Biology of Colias butterflies. 1. The distribution of the North American species. Wasmann J. Biol. 8:49-75.

J

Journal of Research on the Lepidoptera 1(1) :85-88, 1962

1140 W. Orange Grove Ave., Arcadia, California, U.S.A.

DID THE CATERPILLAR EXTERMINATE THE GIANT REPTILE?

S. E. FLANDERS

University of California Citrus Research Center and Agricultural Experiment Station, Riverside, California

The abrupt disappearance of the giant reptile during, the Cretaceous period brought to an end a very successful plant-animal system. For 120 million years the reptile population had roamed over large areas of the earth, subsisting in the lush vegetation covering such areas. From the standpoint of the reptile s subsistence, plant life was unlimited. It was an apparently inexhaustible resource.

The possibility that the great reptiles disappeared as a result of malnutrition and starvation has been considered and discarded as quite untenable. That highly evolved plant-feeding animals do not normally become limited in numbers by starvation is axiomatic. Nicholson (1954) pointed out that the major influence which prevents phytopha- gous animals from reducing the earth s vegetation to extre'me sparseness is their attack by natural enemies.

Exhaustibility of plant life, an inherent characteristic of many plant and animal relations, is rarely realized, being usually precluded through the regulation of the animal population by its natural enemies ( Flanders 1959). Thus, the Cretaceous populations of the vegetarian reptiles, by serving as prey for populations of highly efficient predatory reptiles, were kept at levels well within the limits set by the amount of plant life. At the same time these predators served also to suppress the evolution of competitive types of animals of similar size such as the mammal.

The geological record of the Cretaceous period, however, reveals a series of events which may have culminated in the temporary destruc- tion of vast am.ounts of plant life, a period in which the vegetarian reptiles may have been so devitalized that they either failed to reproduce or fell easy prey to their predatory relatives.

The critical events which could have led up to the disappearance of the giant reptile were: (1) the replacement of the ancient fern- like plants by phanerogamic plants; and (2) the emergence of the Lepidoptera, an insect order which with few exceptions feeds only on such plants (Imms, 1930).

The background against which these events should be visualized

85

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FLANDERS

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is the world-wide dominance of insects both in species and in popula- tion densities, a dominance which existed throughout the Age of Reptiles and the Age of Mammals. The pre-Cretaceous insect fauna appears to have been quite similar in kind and in numbers to the post-Cretaceous insect fauna except for the lack of species which fed on flowering plants (Carpenter 1952). A number of such species were subsequently derived from the pre-Cretaceous insect orders of Coleop- tera, Diptera, Hemiptera, Hymenoptera and Orthoptera, species whose immediate progenitors had presumably already acquired their natural enemies.

According to Imms (1931), it is practically certain that the Lepi- doptera is pre-Tertiary in origin, highly organized individuals being represented in Eocene rocks. The paucity of insects in Cretaceous rocks is attributed to the absence in that period of suitable fresh-water deposits in which specimens could have accumulated and become fossilized.

Plant-feeding insects like other plant-feeding animals acquire natural enemies which serve to conserve the plant life upon which they subsist. The fact that the conservation of plant life is a function of the natural enemies of Lepidoptera has been demonstrated during the past sixty years by the importation and establishment in North America of the natural enemies of the caterpillar for otherwise the reduction in brown-tail moth, Nygmia phaeorrhoea (Donovan), the satin moth, Stilpnotia salicis (Linnaeus), and the larch caseberer, Coleophora laricella (Hubner) (Clausen 1956). During the past three years the writer, by using the grain moth Anagasta and its natural parasite, Exidechthis, has demonstrated in the laboratory the role of a natural enemy in the conservation of plant material. In a constant environment parasitization continuously conserved the plant material despite the presence of a persistent feeding population of Anagasta.

In nature, therefore, a community of plant-feeding animals con- sisting, say, of a pentatomid bug, a grasshopper, a moth caterpillar, a vole, a rabbit, and an ungulate depending on the same resource, grass- land vegetation, can remain stabilized for a long period of years ( Elton 1946). Such stabilization, however, consists in the total amount of plant life conserved, not in the relative abundance of the plant species involved, an abundance determined by the phytophagous animals through their effect on the competitive capacities of the plant species (Wilson 1949).

Devastations of plant life by caterpillars can occur today whenever the regulating action of their natural enemies is disrupted by environ- mental factors. Graham (1939) reported that during a ten-year period ending in 1920 an eruption of the spruce budworm, Choristoneura fumiferana (Clemens), was characterized by flights of moths so numerous that in the tree tops they had the apparance of a snow storm. During this eruption the caterpillars destroyed a volume of wood

(i):85-88, 1962

CATERPILLAR AND REPTILE

87

sufficient to supply all of the pulp mills then operating for a period of forty years.

The capacity of a lepidopteran in the absence of its natural enemies to reduce great areas of lush vegetation to extreme sparseness and to maintain it so thereafter was demonstrated in Australia when the caterpillars of Cactoblastis cactorum (Berg) imported from Argentina in 1925 destroyed within six years approximately 50 million acres of the prickly pear, Opuntia spp. Dodd (1929) in reporting on this devastation stated that great care had been taken not to set free any of the natural enemies of the catrpillar for otherwise the reduction in prickly pear would have been of minor proportions.

It is evident that the plant-consuming capacity of a caterpillar population could equal that of a giant reptile population and that this capacity because of the caterpillar’s very short life cycle could be attained at a much greater rate. Supplementing this capacity was a power of survival much greater than that of the giant reptile, the minimum food requirements of the individual caterpillar being infinitesimal relative to that of the individual reptile.

Nevertheless, there is no reason to believe that the caterpillar and the giant reptile could not have subsisted together on the same vegetation if the caterpillar, immediately upon its Cretaceous emergence, had been subject to a regulation by natural enemies as effective as was that of the vegetarian reptile by its predatory relatives.

The theory that the caterpillar exterminated the giant reptile rests on the assumption that between the emergence of the new insect order and its accessions of regulative natural enemies there occurred a brief period in which the caterpillar population regulated the world’s supply of plant food, a condition conducive to great variations in abundance of plant life and of caterpillar life, a condition characterized by "feast and famine" in which the caterpillar was able to survive but not the great reptile.

The inherent weakness of the reptile was an extraordinary need for an abundance of plant material. Only a few years of plant scarcity could have exterminated it. Hordes of caterpillars, in rapid consump- tion of fig and breadfruit, laurel and willow, oak and magnolia, could have so restricted the spatial distribution of the giant reptile that either its diet was inadequate or it was unable to avoid its natural enemies.

The small size of today’s descendent reptiles, the vegetarian turtle, the predatory crocodile, the snake, and the lizard, is evidence of the giant reptile’s elimination by starvation and predation.

The abrupt end of the Age of Reptiles during the Cretaceous period is ascribed to a newly emerged order of insects, the Lepidoptera, on the supposition that for a brief period it regulated the world’s supply of plant life at starvation levels for the dependent reptiles. Thus, the giant reptiles which had survived during eons characterized by great

88

FLANDERS

/. Res. tepid.

changes in climate, continental uplifts, and different diets may have

been exterminated by the lowly caterpillar.

LITERATURE CITED

CARPENTER, F. M. 1952. Fossil insects. 1952 U.S.D.A. Year Book. pp. 14-19.

CLAUSEN, C. P. 1956. Biological control of insect pests in the continental United States. U.S.D.A. Tech. Bull. No. 113, 151 pp.

DODD, ALAN P. 1929. The progress of biological centrol of prickly pear in Australia. Commonwealth Prickly-Pear Board, Brisbane Qld. 44 pp.

ELTON, CHARLES. 1946. Competition and the structure of ecological communities. Jour. Animal Ecol. 15: 54-68.

FLANDERS, S. E. 1959. Biological control. Jour. Econ. Ent. 52: 784-5.

GRAHAM, S. A. 1939. Principles of forest entomology. McGraw-Hill, N.Y. 410 pp.

IMMS, A. D. 1930. A general textbook of entomology. E. P. Dutton & Co., Inc., N.Y. 703 pp.

IMMS, A. D. 1931. Recent advances in entomology. P. Blakiston’s Son & Co., Inc., Philadelphia. 374 pp.

NICHOLSON, A. J. 1954, An outline of the dynamics of animal popula- tions. Australian Jour. Zool. 2:9-65.

WILSON, F. 1949. The entomological control of weeds. Int. U. Biol. Sci. Ser.B. 5:53-64.

Journal of Research on the Lepidoptera

1(1) :89-93, 1962

FURTHER EVIDENCE OE THE DISTRIBUTION OF SOME BOREAL LEPIDOPTERA IN THE SIERRA NEVADA'

C. H. ERIKSEN

Los Angeles State College, Los Angeles, California

Except where roads penetrate the high country, little or only scanty information is abaiiable concerning the animal life of the high Sierra of California. This condition is extant because these mountains are high, rugged and largely accessible only by trail. The fact also that collecting gear must be packed in and out encourages few people to undertake such studies.

Our knowledge of the Lepidoptera fauna of the Sierra stems largely from the work of Garth (1935) and Tilden (1959). Garth’s study of the Butterflies of Yosemite National Park is notable since he not only provides a list of species taken within the confines of the park, but relates them to the life-zones in which they are normally found to fly. Tilden has refined the latter concept in his Tioga Pass studies by listing associations of smaller scope than life-zones.

While backpacking the John Muir TraiP during the summers of 1953, 1954 and 1955, the author made spot collections of Lepidoptera at various locations along the route (Figure 1). Such was a brief attempt to add information similar to that of Garth and Tilden to our knowledge of the day-flying Lepidoptera in high areas from Yosemite on the north to Mount Whitney on the south. All forms collected and altimdes at which they were taken are listed in Table 1. To alleviate any confusion, all nomenclature is after McDunnough (1938). Altitudes were determined from Starr ( 1953) .

Since Garth (1935) and Tilden (1959) have shown that various species fly only within certain altitudinal ranges while others are unrestricted in their flight, there is little need to repeat similar fiindings here. However, the data collected does extend the known altitudinal range of several species. The following were taken at elevations higher than previously recorded and are associated with the life-zone of this extension.

1 My thanks to Nelson Baker, Santa Barbara Museum of Natural History, for help with identifica- tion of the material and W. Hovanitz for aid in preparation of this paper.

2The John Muir Trail follows a 215 mile route along the Sierra crest from Yosemite Valley on the north to Mount Whitney on the south. Except for a short distance out of Yosemite Valley (elevation 4,000'), altitudes range from approximately 7,000' to 14,I00'.

89

90

ERIKSEN

/. Res. tepid.

Argynnis mormonia (Arctic- Alpine)

Euphydryas chalcedona ( Transition, Canadian )

Lycaena helloides ( Canadian, Hudsonian )

Plebeius aquilo podarce ( Arctic-Alpine)

Plebeius saepiolus ( Arctic-Alpine )

Plebeius icarioides (Hudsonian, Arctic-Alpine)

Plebeius acmon ( Hudsonian )

Garth does not list Lycaena helloides above the Transition zone nor Plebeius saepiolus above the Hudsonian. Even though Tilden does not actually say, he intimates that both species transcend all zones. In the event that any confusion may arise, both species are included in the above list.

It is of interest that those forms listed in this paper, which also are found in Colorado, have already been collected in that state from life-zones here described as extensions (Brown et al, 1957).

LITERATURE CITED

BROWN, F. M., D. Eff and B. Rotger. 1957. Colorado Butterflies. Proc.

Denver Mus. Nat. Hist., Nos. 3-7:1-368.

GARTH, JOHN S. 1935. Butterflies of Yosemite National Park. Bull. So. Cal. Acad. Sci., 34(1) :l-39.

McDUNNOUGH, J. 1938. Check List of the Lepidoptera of Canada and the United States of America: Part L Macrolepidoptera. Mem. So. Cal. Acad. Sci., 1:1-275.

STARR, JR., WALTER A. 1953. Guide to the John Muir Trail and the High Sierra Region. Sierra Club, San Francisco, 130 pp.

TILDEN, J. W. 1959. The Butterfly Associations of Tioga Pass. Wasmann J. Biol., 17(2) :249-271.

I (i): 8^-93, 19^2

BOREAL LEPIDOPTERA

91

92

ERIKSEN

/. Re$. Lepid.

Arctic Alpine

Mather Plateau

11,500* ; 7-30-53

ro

€n

Bighorn Plateau

11,500* 1 7-31-54

bH'

ffH

a-

Tyndall Creek

11,000* i 7-29-54

pH

cO

-

Upper Bubbs Cr,

11,000’ ; 7-29-54

sH

Evolution Lake

10,990* s 7-26-53

a>

Hudsonian

Mdl* Palisade Low, L, 10,650* t 7-28-53

sH

Cascade Valley

10,400* 1 7-5-54

Duck Uke Trail

10,100* s 7-5-54

-

tH

Purple Lake

10,000* S 7-6-54

CD

ffH

OI

1000-Island L.

9,850* 1 6-30-54

OI

■H

(tH

Little Pete Mdw,

9,100* s 7-12-55

O

*H

Shadow Creek

9,000* s 7-1-54

(O

(H

CM

Shadow Creek

8,750* 1 7-2-54

Tuolumne Mdws,

8,700* j 6-29-54

CM

pH

Canadian

Palisade Creek

8,125* 1 7-31-55

eH

CO

Quail Meadows

7,700* 1 7-8-54

CO

iH

tH

.H

ra

Table 1.

John Muir Trail Collection Sites, Listed by Elevation, and the Species and Number Taken

Map Location Number 1

Papilio zelicaon Luc,

Papilio rutulus Luc,

Parnassius clodius Men,

>

-o

m

Q

X

>.

s,

p

«

m

O

o

Colias behrii Edw,

Pieris sisynbrii Bdv,

Pieris occidentalis Reak,

Argynnis montivaga Behr

>

(0

•H

G

0

1 o s

m

G

<

Brenthis epithore Edw,

c

o

•o

0

»H

ns

^ • o »

m X r@

$4

^ *

>, >

3 ^ U Q

Euphydryas sierra Wgt,

«

m

c

•H

a

c

>*

o.

3

M

Melitaea palla Bdv,

Phyciodes laontana Behr

Polygonia zephyrus Edw,

(i); 8^-93. 1962

BOREAL LEPIDOPTERA

93

CO

CM

•H

CM

to

CO

<0

r-t

pH

CO

-

■H

•H

-

CM

tn

eH

-

pH

•H