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1969
Journal of the Lepidopterists Society
251
SEASONAL VARIATION OF COLIAS CESONIA THERAPIS IN VENEZUELA (PIERIDAE)
John H. Masters
Box 7511, Saint Paul, Minnesota
Colias cesonia (Stoll), with its various subspecies, is found throughout Tropical America from northern Argentina to the United States. The subgenus Zerene Hubner, to which cesonia belongs, seems to be tropical in origin and is found throughout the Neotropics at low elevations. The subgenus Colias Fabricius, on the other hand, is worldwide in distribution but is confined to high elevations in the Andes in the equatorial regions of South America. Colias cesonia therapis (Felder & Felder), like many of the other C. cesonia subspecies, is strikingly different in appearance from the nominate race (figure 1). C. c. therapis inhabits the coastal mountain range of Venezuela.
My first experience in collecting C. c. therapis was during the dry season (March 1965) at the Henry Pittier National Park, Aragua, Venezuela. The butterflies were swarming at flowering Lantana on dry slopes at an elevation of about 1,000 feet. All of the C. c. therapis captured had a strong roseate suffusion on the ventral surface of both wings, a character similar to that found in the form "rosa" M'Neill of Nearctic Colias cesonia cesonia populations.
Since that time I have received series of the butterfly from the same location taken throughout the year by Senor Francisco Romero of Mara-cay, Venezuela. Study of these additional specimens showTed that at certain times of the year the roseate suffusion predominates while at
Fig. 1. Colias cesonia therapis (F. & F.), left male, right female, Aragua, Venezuela, March 1965. Actual size.
252 Masters: Seasonal variation in Colias Vol. 23, no. 4
Fig. 2. Correlation of "roseate" form of Colias cesonia thempis (F. & F.) to rainfall and annual broods.
other times it is absent. Apparently there are four broods of thempis annually at Aragua: two are roseate and two are normal (figure 2). The occurrence of the roseate form correlates with the dry season (months of less than two inches of rain), while the ordinary form predominates in the wet season (more than three inches of rain per month). In a series, the extent of roseate suffusion varies widely and I have classified as
1969
Journal of the Lepidopterists' Society
253
"roseate" all specimens showing the tendency to any degree. The examination of 52 $ S and 23 2 2 from Aragua indicates an overall 89.3% correlation of the roseate form to the dry season, and nine $ $ from Caracas have 100% correlation. The material from Aragua and the correlation of coloring with rainfall and broods is shown in graphic form in figure 2.
Trivial names have not been given to either the wet or dry season form of therapis and since seasonal forms are not formally nameable under the International Code of Zoological Nomenclature I see no reason why "rosa" cannot be used as a nomen collectivum for the roseate dry season form of therapis. Colias cesonia cerbera (Felder & Felder) is more than likely the dry season form of Colias cesonia as it occurs in western Venezuela. Both white and yellow females occur in therapis, with white predominating four to one in Aragua, but the female background color has no seasonal correlation.
The form "rosa" is certainly a dry season form which originated in the tropics; quite likely it has spread to the northern regions as a mainly winter form. In the United States the form "rosa" certainly occurs in late fall, especially in the western (drier) part of its range. Wet and dry seasonal forms are not often encountered in the Neotropics, though in Africa where 80 to 95% of the annual precipitation occurs during the wet season, they are quite pronounced in genera such as Colotis and Precis. Brown (1929) suggests that Phoebis cypris (Fabrieius) and Phoebis neocipris (Huebner) are probably wet and dry phases of the same population. The problem, of course, is the lack of exact collecting dates on much of the material from the Neotropics, a lack that has possibly kept wet and dry seasonal forms of many species from being recognized. This same lack of exact data prevented me from using; specimens in both private and institutional collections to supplement my tabulation.
Acknowledgments I gratefully acknowledge the assistance of Senor Francisco Romero, Senor Albert Gadou and Senor Harold Skinner, respectively of Maracay, Caracas and Los Dos Caminos, Venezuela for supplying specimens for study; the late Dr. Richard M. Fox of the Carnegie Museum who read my manuscript and made helpful suggestions in the presentation; and Dr. Alexander B. Klots of the American Museum and Harry K. Clench of the Carnegie Museum who were kind enough to comment on my data.
Literature Cited
Brown, F. M., 1929. A revision of the genus Phoehis (Lepidoptera). Amer. Mus. Novitates, No. 368: 1-22.