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114
Journal of the Lepidopterists' Society
WING COLOR VARIATION IN CALLOSAMIA (SATURNIIDAE)1
Richard S. Peigler
Department of Entomology and Economic Zoology Clemson University, Clemson, South Carolina 29631
The genus Callosamia Packard is comprised of three sexually dimorphic species. Callosamia promethea (Drury) is melanic with males almost black and females a wine-red color. Callosamia securifera (Maassen) and C. angulifera (Walker) have brown males and orange females although the former species is lighter and suffused with yellow. Adults of the latter two species also differ seasonally in that the spring or overwintering forms of both sexes are light and the summer forms are dark. Such seasonal variation has been oversimplified in past literature. It is the purpose of this paper to discuss in greater detail these wing color variations.
Although C. promethea does not have seasonal forms as in the other two species, there is color variation. In males the area beyond the post-median line on the underside of the wings may be either bright red or blue-gray. Both color forms, and intermediates, were found among males collected in spring and summer from southeastern Pennsylvania.
Orange females of C. promethea may occur among populations with normal dark red females. Young (1968) and Baldy (1890) reported such populations occurring in Ulster Co., New York and on Mt. Cata-wissa, Pa., respectively. The possibility of hybridization is unlikely because of effective temporal isolation. Orange C. promethea females are possibly mutations in which the gene (or genes) governing reddish-ness is not expressed.
The pair of C. angulifera which Ferguson (1972, pi. 22, fig. 3, 4) uses to represent summer adults are scarcely darker than spring ones. In upper South Carolina the summer adults of both sexes are nearly as dark as C. promethea and the males have obsolete discal marks as in C. promethea. The winter of 1973-74 was very mild in South Carolina, and the adults of that spring varied through the entire spectrum from light to dark. This included specimens from wild and reared cocoons (kept outdoors all winter) as well as those coming to lights. Apparently, adults are darker when wing scale formation in the pupa occurs under comparatively high temperatures. In fact, C. angulifera cocoons which I overwintered in the refrigerator (40°F = 5°C) yielded dark adults
1 Published by permission of the Director of the South Carolina Agricultural Experiment Station. Technical Contribution No. 1252.
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that match the summer form. The same was true for adult hybrids of angulifera $ X promethea $, although some of their darkness may be attributed to C. promethea parentage. Cocoons of the saturniid Actios luna (L.) which I kept at no lower than 40°F during the winter also produced adults similar to the summer form of that species.
The effect of the mild winter of 1973-74 was further illustrated in the C. securifera population in Berkeley Co., South Carolina. Spring adults began flying in mid-April instead of late April, as they usually do, and most were dark. Although a few golden spring males and blackish summer males emerged from a lot of about 20 cocoons collected in March 1974, most did not fit either form and were intermediate.
Ferguson (1972) stated that females of C. securifera from Florida are paler than those collected from further north. However, specimens in my collection from Florida and both Carolinas do not follow this pattern. Possibly the Florida material available to Ferguson was faded.
In conclusion, seasonal variation in Callosamia is due apparently to effects of temperature on pupae and is not clear-cut without intermediates. There is no constant geographical variation in any of the three species, although seasonal extremes in C. angulifera may be greater in the South.
Acknowledgments
I wish to thank Drs. John Morse and G. R. Carner for reviewing the manuscript and offering helpful suggestions.
Literature Cited
Baldy, S. 1890. [Untitled note.] Ent. News 1: 146.
Ferguson, D. C. 1972. Bombycoidea, Saturniidae (in part). In R. B. Dominick
et al., The Moths of America North of Mexico, fasc. 20.2B, p. 155-269, pis.
12-22. E. W. Classey Ltd. London. Young, A. M. 1968. Color variant of Callosamia promethea (Saturniidae) in New
York. J. Lepid. Soc. 22: 185-186.