﻿120 THE ENTOMOLOGIST. 



American silkworm), and A ttacus cynthia (the Ailanthus silkworm). 

 Platysamia cecropia (North American) might also he added : this 

 species seldom succeeds in England in the open air, as it remains 

 too long in the larval state before spinning, but in Central and 

 South Europe it would thrive splendidly. It feeds on fruit trees 

 and most forest trees. The larva? of the first four species produce 

 fine and excellent silk and form " closed " cocoons, the last two 

 " open " cocoons. As I have mentioned P. cecropia I may, I 

 think, be allowed to make a little digression. 



Mr. T. D. A. Cockerell has published (Entom. xxii.) several 

 interesting articles on the " Variation of Insects," and (page 177 

 of that volume) he invites those who possess dwarfed Lepidoptera 

 to examine them and report on the sex. The paragraph referred 

 to runs thus : — 



" Lepidoptera may be dwarfed in captivity, by giving the 

 larva? an insufficient supply of food, and it has been stated that 

 these dwarfs are generally of the male sex. Mr. T. G. Gentry 

 (Can. Ent. 1877, 50) believed he could influence the sex of insects 

 in this way, and out of twenty Samia cecropia so reared eighteen 

 proved to be males. It would be interesting if all those who 

 possess dwarfed Lepidoptera would examine them and report on 

 the sex." 



Now I quite agree with the first statement, that an insufficient 

 supply of food will produce dwarfed individuals ; but with respect 

 to the second statement, that the dwarfs will generally be of the 

 male sex, this I consider erroneous and only accidental. I never 

 was more surprised than when I read that the sex of insects 

 could be influenced in any way. It comes to this — that an insect 

 which, with a sufficient supply of food, would have been a female, 

 will turn into a male if kept short of food. In no other sense 

 can I understand the statement. I have had considerable expe- 

 rience with the breeding of cecropia moths from cocoons received 

 from North America. This year I received 1500 cocoons, — 

 nothing compared with the number sent to me in 1878, which was 

 5500. For years I have had this species of Samia, and I never 

 noticed that the number of male dwarfed specimens exceeded in 

 any permanent degree the number of female specimens. Some- 

 times the males will predominate, and sometimes the females. 

 This year a small number of cecropia larva? were bred here in 

 captivity, in Norbiton, by one of my neighbours, who brought me 

 the thirteen cocoons obtained. All were very small, but male 

 and female moths (about half the natural size, and even less) 

 emerged from the cocoons, only one pupa having died. Of the 

 American cocoons, not bred in captivity, but all collected in the 

 country, a number of dwarfs were found, as is often the case ; 

 and male and female moths emerged from these tiny cocoons in 

 about equal numbers. From a hundred Callosamia promethea 



