NATURAL SCIENCES OF PHILADELPHIA. 281 



INFLUENCE OF NUTRITION ON SEX AMONG THE LEPIDOPTEEA. 

 BY THOMAS O. GENTRY. 



That the sexes among plants ^a're controlled bj^ the law of nu- 

 i7'ition, I think has been demonstrated b}^ Mr. Thomas Meehan, in 

 his communications to the Academ}^ of Natural Sciences, published 

 in its proceedings, in the American Nafuralid, and in other scien- 

 tific journals. The facts which appear in his contributions upon 

 this subject were the results of close research and careful stud3^ 

 To him must be ascribed, not only the credit of having established 

 the existence of the afore-mentioned law, but also the hint of its 

 potency in animals. 



Mrs. Mar}^ Treat, I believe, is entitled to the credit of first 

 showing its applicability in insects, in a paper which appeared in 

 the American Naturalist for March, 1873. The facts set forth in 

 her paper were founded on observations upon the larviB of some 

 species of Diurnal Lepidoptera during the summer of 1872. The 

 inferences which she drew from her observations were substantially 

 as follows: Whenever the larvae were deprived of food, or were 

 stinted in quantity, in the interval between the last two changes, 

 males were produced in the generality of cases ; but when the 

 food was regularly supplied, and in bulk necessary for the wants 

 of the larvse, the opposite sex was almost invariably produced. 



The facts which I have to offer bearing upon the genesis of 

 sexes, date back to the summer of 1871, whilst engaged in the 

 rearing of the larvse of many of our Twilight and Night Fliers, 

 and in the study of their various metamorphoses. The discovery 

 was the result of accident : I had confined a number of the larvse 

 of Atfacus cecropia^ A. poUjphemus^ A. pirometheus, and Saturnia 

 lo^ in a box, and had neglected to supply them with food for four 

 days. These larvse had advanced toward their final change, 

 possibl}' within a week or ten days. When I opened the box, the 

 greater number, which fell not much short of a score and a half, 

 had concealed themselves within cocoons ; the remainder still 

 wandered about, as if in quest of food, or seeking for some 

 opening through which to escape. These latter I removed from 

 the box to another, where they were provided with an al)undance of 

 food. Thej^ immediately recommenced feeding. After three or 

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