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1955
The Lepidopterists' News
79
FIELD NOTES
SEXUAL DIMORPHISM IN LEPIDOPTEROUS LARVAE
With reference to the last paragraph of ALICE L. HOPF'S short paper (1954, Lepid. News 8: 124), sex can be determined in quite a number of Lepidopterous larvae.
In many thin-skinned and lightly pigmented larvae (good examples can be found among the Pieridae and Hesperiidae), the male gonads can be plainly seen through the skin of the dorsum.
In the Lymantriidae, many species have an extra larval instar in the female, and the full grown larvae of the females can be easily recognized by their greater size. Strangely enough, the Lasiocampidae do not seem to have this extra instar, although the female imago is often very much larger than the male.
I imagine, however, that the query really refers to differences in colour or pattern. I have recently come across one such case. The African lymantriid, Dasychira georgiamt Fawc, is, I believe, unique in exhibiting a sex-controlled larval form. The larva is dimorphic; it may be black with black dorsal tufts or green with yellow ones, and there is a sex-controlled female form with a broad orange-red lateral stripe. An account of the genetics of this sex-controlled mutant can be found in The Entomologist 85: 88; 1952.
D. G. SEVASTOPULO, F.R.E.S., P. O. Box 401, Kampala, UGANDA
MASS FLIGHT OF OCOLA SKIPPERS
Although the stimuli responsible for inducing mass flights of insects (migratory or otherwise) remain a mystery, the occurrence of such flights continues to be of interest to biologists generally. Despite the lack of acceptable hypotheses concerning non-migratory mass flights, each notable one should be recorded in the hope that cumulative data will be of use in a solution to the problem.
It is with this thought that the writer (no lepidopterist) records a mass flight of Panoquina ocola (Edwards), a common southern skipper. At about 3:00 p.m., on October 15, 1950, the writer and ELSIE W. Smith, a graduate student, encountered thousands of P. ocola flying NNE over Pointe aux Herbes, Orleans Parish, Louisiana, on the southeastern shore of Lake Pontchartrain. The skippers were flying rapidly at from four to twenty-five feet above the surface (land or water) across a mild (11 m.p.h.) east wind, temperature about 80°F. The skippers were first seen on the U.S. 11 highway bridge over the lake about a mile north of the shore and were abundant for about one-quarter of a mile inland. No estimate of the width of the flight could be made. At the end of the bridge it was necessary to drive off the highway to clean the car's windshield which was by then covered with squashed skippers. A few specimens were picked up at the edge of the road from the "windrow" of skippers which had been killed by other passing automobiles.
This species is widespread in southern Louisiana, but neither JUNG (1950) nor LAMBREMONT (1954) recorded P. ocola from Orleans Parish, and nothing has been recorded of the habitat of the immature stages. The geographic origin of the flight, of course, remains unknown, but it seems pertinent that for nearly fifteen miles to the ESE, in line with the flight, the area is covered by fresh-water marshes and swamps.
Specimens were identified by Dr. RALPH L. CHERMOCK of the University of Alabama, and are deposited in the Tulane collections (no. 2220).
References Cited
Jung, Rodney C, 1950. An annotated list of the Lepidoptera of the New Orleans area.
Proc. La. Acad. Sei. 8: 42-48. Lambremont, Edward Nelson, 1954. The butterflies and skippers of Louisiana. Tulane
Stud. Tool. 1 (10): 125-164.
GEORGE HENRY Penn, Tulane University, New Orleans 18, La., U.S.A.