The Papilio Glaucus Group"'
1958 The Lepidopterists' News 103
LARVAL FOOD PLANT SPECIFICITY IN BUTTERFLIES OF THE PAPILIO GLAUCUS GROUP"'
by LINCOLN P. BROWER
The Pap'ilio glaucus group contains three species (P. eurymedon Bois duval, P. mu/ticaudatus Kirby, and P. rutulus Boisduval) which occur to gether over extens:ve areas of the western United States, and a single almost entirely alJopatric one (P. glaucus Linne) which is widely distributed in northern and eastern North America. In addition to these four, the group includes P. alexiares H opffer which occurs only in the mountainous regions of eastern .Mexico. On the basis of larval, pupal, and male genital characters, it was shown that the three western butterflies are morphologically closer to each other than anyone is to P. gLaucus, and that P. pilumnus Boisduval be longs to the P. troi/us Linne group (Brower, in press, a). In order to understand the pattern of speciation in such a group of closely related animals, it is necessary to know the similarities and differences in their ecological requirements, one of the most important of these being food. The purpose of this paper is to present a critical review of the published records of the larval food plants of the butterflies of the Paf,ilio glaucus group to which will be added new data gathered by my research activities in the west ern United States during 1954-1956 and obtained through the cooperation of members of the Lrpidopterists' Society. Dur to the extensive sympatry of the three western butterflies and the similarity of their larv~, which have never been figured together in a single plate until the present publication (see figure), considerable error has un doubtedly been introduced into the literature by authors who did not rear eggs and/or larv~ found in the wild to the adult stage for positive identifica tion. Moreover, the only larval figure of P. eurymedolZ, first published by EDWARDS (1884) and later repu bl ished by COMSTOCK (1926, 1927), was based on a drawing which inaccurately represented the eye-spot pattern on the thorax of the fifth instar larva. A second source of error arises from the fact that it has only recently been established (Brower., in press, a) that the distribution of P. glaucus overlaps the northern extremity of the range of the three western species in southern British Columbia. A third is that worn females of P. glaZlcZls, P. rutulus, and P. eurymedolZ are almost indistinguish able in flight, which means that oviposition records themselves are subject to error. Fourth, and finally, several later authors have cited earlier ones who were undoubtedly mistaken for the above reasons. Because of these possibilities for confusion, all published records for each of the western species have been divided into three categories and tabulated (Tables 1-3). The first category summarizes the data given by authors who documented their records. Authors 111 the second category gave food plant records with insufficient or no support-
*Submitted to the faculty of the graduate school of Yale University as partial ful fillment of the requirements for the degree of Doctor of Philosophy, May, 1957. Other portions of the dissertation are being published elsewhere. 104 BROWER: Papilio foodplants Vo1.12: Ilos.3-4 ing data. Those of the third definitely or apparently cited some or all records from previous publications. Such a stringent breakdown for P. glaucus is not necessary because most of the records are from eastern North America where confusion with the western species is impossible. Therefore, only a short discussion of the larval food plants of P. glaucus is included. No food plants have ever been recorded for P. rzlexiares. 1. Larval Foodplants of P. glaucus P. glaucus has been reported feeding on more species of plants in a greater number of families than any other member of the P. glaucus group, but there appears to be a tendency for different preferences in different locali ties. For example, EDWARDS (1885) reported that neither he in Coalburgh, West Virginia, nor J. AKHuRsT in Brooklyn, New York, had ever found larv::e on Salix spp. Previously EDWARDS (1884) had reported that he had attempted to force P. glazu'us larv::e to eat willow without success, but in 1886 he published several records which indicated that in northern New England, Salix is a common foodplant of this swallowtail. Following SCUDDER (1889), CLARK and CLARK (1951) stated that Fraxinus spp., Magnolia, and Lirio dendron tulipifera Linne are favorite food plants in the southeastern part of the range of P. glaucus, but in the northeast the main food plants are Prunus, Betula, and Populus. Data very kindly given to me by Drs. K G. MUNROE and T. N. FREEMAN which were gathered by the Canadian Insect Survey
•T em • .1
Last (5th) ins tar larvre of Papilio multicaudatus (top), P. rutulus (center), and P. eurymedon (bottom). The larvre of P. multicaudatus and P. eurymedon have attained th eir maximum size while that of P. rutulus has not. From Kodachrome by L. P. Brower, Boulder County, Colorado, August, 1955. For comparison with P. glaucus, see Clarke & Sheppard, Lepid. News 11: 201-205; the larva of P. eurymedon figured here is the same as in their paper. 1958 The Lepido plerists' News 105
from 1947 to 1955 in southern Canada indicated the following larval fre quecics on plants from Ontario to Alberta: Betula J\apyrifera Marsh, 52; Populus tremuloides Michx., 43; Salix spp., 22 ; M alus pumila Mill, 14; Alnus spp., 12; Sorbus americana Marsh, 10; Prunus spp., 10; Betula lutea lVIichx., 6; Fraxinus americana Linne, S; Populus tacamahacca Mill, 3; A cer spp., 3; Fraxinus pennsylvanica var. lanceolata (Borkh,,) Sarg., 1. P. gLaucus is thus a polyphagous species eating plants in the families Rosaceee, Oleaceee, Salicaceee, Corylaceee, Magnoliaceee, Betulaceee, and Acer aceee, as well as others (see Scudder, 1889). 2. Larval Foodplants of P. rutulus I t can be seen in Table 1 that plants in the families Salicaceee, Plata Ilaceee, and Corylaceee are the only documented food plants of P. rutulus. In spite of the fact that several authors state that plants of the family Rosaceee serve as food of P. rutulus, the records with data do not support this view. MEAD (1878) found that although a captive female oviposited on Prunus sp. when confined in a bag about a branch of this plant, the larvee died after their first molt. He fu rther reported that six other females under similar conditions would not oviposit at all. EDWARDS (1884) reported that W. G. WRIGHT was likewise unable to obtain eggs by confining females over apple or cherry, although they did lay on Salix lasiolepis Benth. and S. lasiandra Benth. ]VIOl·eover, as mentioned below, EDWARDS' first instar larvee chose willow over apple, cherry, and Tulip Tree when presented with leaves of these four plants. Further evidence that Prunus is not a food plant of P. rutu Ius was indicated from the results of collecting larvee during 1955 in Boulder County, Colorado, when an extensive search of Prunlls virginiana Linne pro duced numerous larvee of P. Irlulticalldatus. but none of P. rutulus. (Weber's handbook. 1953, was used to determine all Colorado plants.) During the same summer, Dr. P. M. SHEPPARD and I observed a female laying one egg on Populus angustifolia James (N arrowleaf Cotton wood) along Left Hand Creek at 6,950 fe et altitude. The larva which hatched from this egg was reared to the adult stage on P. tremuloides (Quaking Aspen). This latter species was searched assiduously along the south-facing slopes of Left Hand Canyon, but no larvee were found on it. I t seems probable that the large cottonwoods along the creek are the princi pal food of P. rutulus in this area, but due to the large ,ize and inaccessibility of these trees it was not possible to confirm this view even though individuals which appeared to be ovipositing females were often seen fluttering about them. (That they were ovipositing is supported by our discovery of two eggs on cottonwoods along Big Cottonwood Creek in Salt Lake County, Utah during .T uly 1956; the resultant larvee were positively determined as P. rU lulus). Dr. C. L. R EMINGTON informed me that he in 1955 had found several larvee on the aspens at the University of Colorado Science Lodge which is not far from Left Hand Canyon, but at a higher altitude (9,500 feet). The absence of larvee on the aspens of the south facing slopes of this canyon and their apparent limitation to the cottonwoods along the creek may be related 106 BROWER: Papilio foodplants Vo1.12: nos.3-4 to the presence of larvx of P. ellryrnedon and P. Inliltiwudatus on these slopes. It is possible that natural selection has favored this microgeographical separa tion of P. rutu/us from the other two due to some adverse larval interaction resulting from their occurrence together on the same slopes. (See, for ex ample, Brower, 1958). In Boulder, Colorado, I obtained two larvx from Weeping Willow in September 1956. Several experiments on the suitability of L. tulipifera (Tulip Tree) as food for P. rutulus have been carried out which are particularly important due to the fact that this plant is one of the principle foods of P. glaucus in the southern part of its range. In a letter, F. P. SALA stated that wild P. rutulus females had oviposited for two successive years on an imported tree he had planted in his yard at Burbank, California, but the larvx would not eat the leaves. This confirmed the report of EDWARDS (1884, 1885) who in West Virginia tried to feed the leaves to larvx hatched from eggs sent to him by W. G. WRIGHT from California. According to EDWARDS, nine hatching larvx ate them sparingly before dying a few days later. He offered larvx from the next lot of eggs a choice of willow, cherry, apple, and Tulip Tree and on the subsequent day all were found feeding on the willow (Golden and / or Weeping), which they ate successfully. CLARKE and SHEPPARD (1955) again indicated that P. rutulus will oviposit on L. tulipifera. They hand-paired a female (ex-pupa from Washington state) with a P. glaucus male (ex-pupa from Illinois) and the captive female laid twenty-one eggs on it. Unlike the pure P. rutu/us in the above experiments which refused to eat,
TABLE 1 OVIPOSITIO.'\I AND FOODPLA.'\IT RECORDS FOR PAPlLlO RUTULUS Plallt Species Plant Family Region Source Stages, etc.' I. DOCUMENTED RECORDS. Salix lasiolepis Salicacex Calif. Edward~, 1884 0; I; A2; (n) Salix lasiandra Sa licacex Calif. Edwards, 1884 0; I; A2; (n) Salix sp. Salicacex Calif. Wright, 1892 I; L; (n) Salix spp. Salicacex See text Edwards, 1884, A; (15 ) 1885 Salix sp. Salicacex Calif. Edwards, 1883') 0; (1 ) Salix sp. Salicacex Colo. See text LF; L; (2) Populus sp. Salicace,e Calif. Edwards, 1884 LF; L; ( ?) Populus tremu/aides Salicace;e Cnlo. (Remington) , LF; A; (n) see text Populus angustifolia Salicaccx Coin. See text 0; (1 ) Po pulus sp. Salicacex Utah See text E; L; (2) Platanus Platanacex Calif. R. ]. Ford, LF; A; (n) in litt. A I nus 'Viridis" Corylaceae Calif. Edwards. 1882 0; L; (3 ) Prunus ("cherry" ) Rosacex Calif. Mead, 1878 I; P; (20) Liriodendron lulipifna Magnoliacex See text Edwards, 1884, P; (9) 1885 Liriodendron tulipi/era Magnoliacex See text (SaI3), see text 0; K; (n) Liriodendron tulipifera Magnoliacex See text Clarke & Shep- I; (21) pard 1955 1958 The Lepidopterists' News 107
II. STATED FOODPLANTS. Salix Salicace", w.N. Am Essig, 1946 Salix lasiandra 4 Salicace", B. C. Jones, 1951 Salix spp.' Salicace", B. C. Jones, 1951 Salix Salicace", Colo. Brown rt ai., 1956 Popuius trirhorarpta4 Salicace", B. C. Jones, 1951 Populus spp. Salicace", Colo. Brown et al., 1956 Platanus Platanace:E w. N. Am. Essig, 1946 Alnus Corylace", w. N. Am. Essig, 1946 "Amygda lacc"," Rosacea! 2alif. Behr, 1884 Prunus Spp.5 Rosacea: w. N. Am Essig, 1946 Rubus spp. Rosacea! w. N.Am. Essig, 1946 Pyrus maillS Rosace", w. N. Am. Essig, 1946 Pyrus malus' Rosace", B. C. Jones, 1951 Prunus emarginata4 Rosacea! B. C. Jones, 1951 Betula4 Betulace", B. C. Dyar, 1904 Ptelea baldwini;6 Rutace:E Calif. Comstock, 1921, 1927 Persea gratissima Laurace", w. N. Am. Ess.ig, 1946 Ill. Authors with some or all records definitely or apparently cited from previous publications include Elrod (1906), \Vright (1906), Comstock (1921, 1927), Jordan (1924), Holland (1930), Garth (1935,1950), and Macy & Sbepard (1941).
1 In this column: 0 = oviposition observed in nature; I ~ oviposition induced in captivity; R ~ refused to feed; P ~ fed and then died (plant toxic?); E ~ found as wild egg; LF ~ found as wild larva; L ~ reared to larva; C = some reared to pupa; A .= some reared to adult; the last item, in parentheses, shows the numher of individuals ("n" means several). 2 Inferred from context . ., Died of "neglect" during fourth instar. 4 Confustion with P. glall(1ls possible in British Columbia records. 5 "apricot, cherry, prune; wild cherry, wild plum." 6 COMSTOCK in litt. has told me that he was referring tn Ptelea baldwini; when he published the vernacular name, "Hop" (1921, 1 n7). MACY & SHEPARD (J 941) incorrectly iter preted this "Hop" as Humulus. or ate leaves and then died, these hybrid larv::e accepted them and survived. These results suggest that the ability to eat L. tulipi/era is a genetically con trolled dominan t character. The same larv::e also ate Syringa (Oleace::e) for a sbort period when supplies of Liriodendron were low. In conclusion, P. rutulus appears to be mainly restricted to the Sali cace::e, Platanace::e, and will perhaps eat Alnus viridis DC. of the family Corylace::e. Although it is much more restricted in its diet than P. glaucus, both have main food plants in common; P. rutulus also differs from P. glaucus in being unable to eat L. tulipi/era, even though hath will oviposit on it. This difference appears to have a genetic basis with dominance for Liriodendron feeding. 3. Larval Foodplants of P. multicaudatus It can be seen in Table 2 that plants in the families Rosace::e, Oleace::e, and Rutace::e are the only documented food plant records for P. multicaudatus. The statements that Populus and Salix are foods are not based on data. 108 BROWER: Papilio foodplants Vo1.12: nos.3-4
Plants of the family Oleace TABLE 2 OVIPOSITION AND FOODPLANT RECORDS FOR P/JPfLIO MULT1C/JUDATUS Plant Species Plant Family Region Source Stages, etc. 2 ------1. DOCUMENTED RECORDS. Prunus 'Virginiana Rosacea: Colo. See text I; E; LF; A; (143 ) Pnllllls ("wild cherry") Rosacea: Nevada Edwards, 1874 LF; A; (10+ ) Prunus 'Virginiana2 Rosacece Calif. Pronin, 19 ,; 5 0; I; E; LF; A', ( ? Ligustrum /u(idam3 Oleacea: Mexico' Ruelas, 1925 LF; C; (2) Ligustrum 'Vu/ gare Oleacea: Texas Kendall, 1957 O', C', (1 ) Fraxiulls Uq;iridis)) Oleacea: Mexico4 Ruelas, 1925 LF; C; (1 ) Fraxinus sp. Oleacea: N. M. (Merritt) , E; LF; A; (9) see text Ple/ca cngustifoiia Rutace a:: Texas Kendall, 1957 LF; (30+) Prllnlls vlrglnlana Rosacea: Ctah Snyder, 1894 0; (3 ) PrUllUS americana Rosace", Colo. Edwards, r ; (50) 1883a /Jmelanchier sp. Rosacea: B. C. McDunnough, 0; (1?) 1927 II. STATED FOODPLANTS. Prllilus 'VlYguliana Rosacea: Calif. Behr, 1884 Prllnlls spp. Rosace", w. N. Am. Wright, 1906 Pranas 'Virginiana2 Rosacere Calif. Comstock, 1921 Prunus capuli Rosacea: Mexico Ruelas, 1925 Prllnus cerasus & spp. Rosacea: B. C. Jones, 1951 Pranus ("wild cherry") Rosacea: Colo. Brown et al., 1956 Fragaria5 Rosacea: Calif. Comstock, 1927 Fragaria Sp.5 Rosacece B. C. Jones, 1951 /J melanchier sp. Rosacea: B. C. Jones, 1951 Rosa Rosacece Colo. Brown et al., 1956 Fraxi1lus oregonia Oleacca:: Calif. Williams, 1905 Frax;1lus Oleace", Calif. Comstock, 1927 Frax;nus Oleacea: B. C. Jones, 1951 Salix Salicacea: Calif. Comstock, 1921, 1927 Salix spp. Salicace", B. C. Jones, 1951 Salix Salicacea: Colo. Brown et ai., 1956 Populus Salicace III. Authors with some or all records defin.itely or apparently c!ited from previous publica tions include Jordan (1924), Holland (1930), Davenport & Dethier (1937), Essig (1946), and Garth (1935, 1950). 1 For symbols in this column, see footnote 1 of Table 1. 2 "Prunus de7nissa)J " "L japan/cum", according to STANDLEY (1920-1926), ~ L. lucidum. 4 Species is certain because no other members of the Papi!io glauws group occur in the Federal District of Mexico. 5 Apparently based OIl WRIGHT'S (1906) suggested possible foodplants. 110 BROWER: Papilio foodplants Vo1.12: nos.3-4 I n conclusion, it appears that the foodplants of P. multi'Wudatus are in the families Rosace;:e, Oleace;:e, and Rutace;:e and are thus different from the foods of P. rutulliS. As in the latter species, P. multicalldatus is more re stricted in its diet than P. glallcus and the two have main food plants in common. It will be interesting to discover whether P. mlilticaudatus favors Oleace;:e in the southern part of its rangs and Rosace;:e in the Northern part, for if it does, there would be a striking parallel with P. glallcus which appears to have these geographic preferences. 4. Larval Foodplants of P. eurymedon 1 t can be seen in Table 3 that the only documented food plants for P. eurymedon belong to the family Rhamnace;:e. As in the case of P. rufu{us, plants in the family Rosace;:e purported to be the food of P. eurymedon are not s.upported by full data. Of the three western species, females of this one seem the most prone to ovipositIOn errors. REMINGTON (1952) reported an observation made by W. H. EVANS in California that females each year laid a few eggs on a culti vated J asminllm (Oleace;:e) which the larv;:e would not readily accept. On one occasion, after the larv;:e had only nibbled at these leaves for a few days, they were transferred to Rhamnus cro[ea N utt., but all died. Moreover, F. P. SALA of Burbank, California, reported in litt. that he had observed fe males laying on Prunus persica Stokes (Peach) which he said the larv;:e would not eat. However, he has taken eggs from this plant and reared the larv;:e successfully on Rhamnus. It is thus apparent that representative plants of two families which comprise the main diet of P. multicalldatus are unsuitable for P. eurymedon even though females occasionally oviposit on them. While collecting larv;:e in Left Hand Canyon during August, 1955, we assiduously searched but failed to find any eggs or larv;:e on Ribes inerme. However, a female P. ellrymedon apparently erred in laying a single egg on this plant when pursued up the canyon-side by Drs. C. L. REMINGTON and P. M. SHEPPARD. REMINGTON (1952) reported an observation of D. EFF who saw a female deposit one egg on Cratcegus rivularis Nutt. near Rabbit Ears Pass, Colorado. The fact that a thorough search of Crata:gus erythopoda near Left H and Canyon in 1954 yielded no results, suggests that this, too, may have been an error. McDuNNOUGH'S (1927) report that he observed a P. eurymedon female ovipositing on A {nus in the Seton Lake Region of British Columbia requires confirmation for the reason noted in Table 3. During the search for larv;:e in Left Hand Canyon in 1955, 66 larv;:e of P. eurymedon were found on Ceanothus fendleri on the south-facing slopes. Several of these were preserved, and several yielded adults the following year. In spite of the fact that we searched Prunus virginiana, P. americana, and Populus tremuloides as well as Ribes inerme, no P. eurymedon larv;:e were found except on C. fendleri. We also looked on the leaves of Ceanothlls velu tma Doug!., which is a morc localized species in Boulder County, but found IIO larv;:e on it. Their absence on this plant may be due to the gummy sub stance coating its leaves. The only other member of the family Rhamnacex in this area is C. ovatus Desf., but this plant was so rare in Left Hand Canyon 1958 The LepIdopterists' News 111 TABLE 3 OVI POSITION AND FOODPLANT RECORDS FOR PI/PILIO EURYMEDON Plant Species Plant Family Region ~;our c e Stages, etcl ------'----~=------'------I. DOCUMENTED RECORDS. Geanotlius /endleri Rhamnacea: Colo. See lext E; LF; A; (78) Rhamnus cali/ornica Rhamnacea: Calif. Edwards, 1874 LF; A; (?) Rhamnus rali fornica Rhamnacea: Calif. Dyat, 1892,3 E; LF; A; (?) Rhamnus sp. Rhamnacea~ Calif. (Sala), see texl L; C; A; (?) Geanothus sp. Rhamnacea: B. C.:2 Dyar, 1904 E; LF2; (?) Geanothus sp. Rhamnacea: Wash. (Anderson),3 0; (n) Ceanothus pros/eratus Rhamnacea: Calif. Lembert, 1894 0; (?) iastnillZlln sp. Oleacea: Calif. Remingwn, 1952 0; P; (n) Prunus persica Rosacea:: Calif. (Sala), see text 0; R; (n) GratlPgus rivularis Rosacece Colo. ReminghJll, 1952 0; (1) Ribes ineYme G rossul a riacere Colo. (Sheppard) , 0; (1) see text Alnus sp. Corylacea: B. C.4 McDunnough, 0 4 ; (n) 1927 II. STATED FOODPLANTS. Rhamnus cali/ornica Rhamnacea: Calif. Garth, 1935 Rhamnus cali/ornica Rhamnacea: w. N. Am. Essig, 1946 Ceanothus spp. Rhamnacea: w. N. Am. Essig, 1946 Ceanothus sanguineuJ Rhamnacea: B. C. Jones, 1951 S pircea discolor Rosacea: B. C. Jones, 1951 CratlPgus brevispina Rosacea: B. C. Jones, 1951 Prunus fmarginata Rosacea: B. C. Jones, 1951 A11lelanchier altli/olia Rosacea: B. C. Jones, 1951 Pyrus malus Rosacea: B. C. Jones, 1951 Alnus rubra Corylacex B. C. Jones, 1951 III. Authors with some or all records definitely or apparently cited from previous publica tions include Strecker (1878), Behr (1884), Elrod (1906), Wright (1906), Comstock (1921, 1927), Jordan (1924), Holland (1930), and Davenport & Dethier (1937). , For symbols in this column, sec footnote 1 of Table l. 2 D YAR (1893) described the life history of P. eurymedoll. It is therefore assumed that he correctly determined these larvx. 3 III litt. from ANDREW ANDERSO N of Pateros, Washington. 4 Confusion with P. rululus or P. glau(lls possible if females of the three species were lvorn. that no significant observations could be made. In AUgLl~;t 1956, 12 additional larv Summary and Conclusions 1. This paper is a critical review of foodplant preferences in the five species of butterflies comprising the Papilio glaucus group (P. alexiares, P. eurY771edon, P. glaucus, P. muLticaudatus, and P. rutulus). New data are also presented. 2. There are four sources of confusion in the literature which have been considered in arriving at the conclusions presented here: (a) the primary source is that authors have very often faiLed to indicate whether they reared larvc[' through to the adult stage for positive identification. This is an absolute necessity due to the combination of the extensive geographic cooccurrence of P. eurymedon, P. 77lulticaudatus, and P. rutulus and the similarity in appear ance of their larvx, which have never been figured together until this paper. (b) It has only recently been established that P. glaucus overlaps the northern extremity of the range of the three western species in southern British Columbia. (c) Worn females of P. glaucus, P. rutu/us, and P. eurymedon are almost indistinguishable in flight, which means that oviposition records are subject to error. (d) Several later authors have cited earlier ones mis taken for the above reasons. 3. No food plant or oviposition references exist for P. alexiares. 4. Tables 1-3 constitute all data known to the author regarding the three western species. Such a breakdown for P. glaucus is not necessary be cause records are from the East where it occurs alone and confusion with other members of the group is therefore impossible. TABLE 4 Summary of Foodplant Specificity in the Papilio glau(lls Group, from Tables 1-3. (+ = suitable, - = unsuitable, 0 = no definite records) --- - Foodplant Papilio Species Family glaucus lllulticaudatus nltulus eurYllledon Rosacex + + Oleacex + + 0 Salicacex + 0 + 0 Corylacex + 0 + 0 Rhamnacex 0 0 0 + Magnoliacex + 0 0 Platanacex 0 0 + 0 Rutacex 0 + 0 0 Others + 0 0 0 The food plants of P. alexiares are unknown. 1959 The Le pidopterists' News 113 5. P. glaucus is a polyphagous species feeding on plants of several families. But unlike it, each of the three western ones is restricted in its food plant diet even though two of them have foodplants in common with P. glaucus. Moreover, the three western species are mutually exclusive in their foodplant diet (Table 4). 6. These facts suggest that competition among the western species dur ing the larval stage has resulted in their restricted and mutually exclusive diets. I have elsewhere described how this may have occurred (Brower, 1958) , and adult as well as larval compet'tJOn among them has been dis cussed in another paper (Brower, in press, b). ACKNOWLEDGMENTS I should like to express my appreciation to Dr. C. L. REMINGTON of Yale U niversity for originally suggesting the Papilio giaucus group study and for his help and advice throughout its development; also to Professor G. E. HUTCHINSON and Dr. E. S. DEEVEY, JR., who gave me much useful advice and criticism. I am indebted to Drs. P. F. BEl.L1KGER and W. D. HARTMAN of Yale for criticizing the manuscript. Thanks also are due those members of the Lepidopterists' Society mentioned in the paper. Dr. E. B. FORD, F. R. S., of Oxford University is to be especially thanked for his hospitality at the G en etics Laboratory where considerable revisiun of the paper was carried out. I am grateful to Drs. J. W . MARR, A. W. JOH NSON, and W. OSBURN for providing me with facilities for the field work at the Institute of Arctic and Alpine Ecology, Uni versity of Colorado. Mr. D. EFF and Mr. and Mrs. H . FREUDENBERG provided in valuable assistance in the field work as did Mr. R. H. WILSON. I also want to thank Mrs. INA GILES of Amherst College for typing the final manuscript. I am greatly in debted to my wife, Dr. JANE VAN ZANDT BROWER, of Muunt Holyoke College, for con tinual help and encouragement. This publication represents one aspect of my research at Yale supported during 1954-1957 by grants from the Sigma Xi RESA research fund', the Higgins Fund of Yale U niversity, two predoctoral National Science Foundation Fellowships, and a Fulhright Scholarship at Oxford during 1957-1958. Literature Cited Behr, H. H., 1884. Biological synopses of California Lepidoptera. Bull. Calif. A cad. Sci. 1: 63-65. Brower, L. P., 1958. Bird predation and foodplant specificity in closely related pro cryptic insects. Amer. 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