experiments on some Le]u<lopt''ra. 143 



treatment can — I do not say in all cases — either give 

 the required predisposition, or, where it exists naturally, 

 can completely reverse it. 



Perfect Insects, icing. — From the 20th to the 23rd 

 July I iced 5 male and 2 female illustraria, a day or two 

 after their emergence. They were frequently looked at 

 and seemed in a lethargic condition, nearly motionless, 

 reviving, however, immediately in the warm air of the 

 room. By the 15th September, i. e., after about 55 days, 

 they seemed less inclined to move, and I placed them 

 for an hour or two at a cooling temperature, and then 

 in the air of the room, where the temperature was about 

 64°. One female was dead ; 5 males and 1 female were 

 alive and could flutter a little, but only one was able to 

 crawl up the side of the box ; and, after keeping them 

 for a day or two, they showed no signs of reviving. 



Incidental Matters. — (1) Male longer in pupa than 

 female. — The experiments recorded last j'ear indicated 

 that in the species operated on the pupal stage was 

 longer in the male than in the female. With a view to 

 place this matter beyond doubt, I made some exact 

 experiments by noting as closely as I could the time of 

 (1) spinning-up, (2) pupating, (3) emergence, and found 

 myself able to carry out the observations very accurately. 

 They gave the following results : ~ 



autumnaria (forced). Table VI. 



The extreme regularity of the period of duration in 

 all cases will be noted : the slowest female was con- 

 siderably ahead of the fastest male. As the males and 

 females emerged at the same time, the male must have 

 been on the average earlier to pupate than the female, 

 from which it follows either that the male feeds up 

 faster than the female, or that the female hatches earlier, 

 a thing quite possible, as the hatching in this species 

 extends over a period of many days. A practical con- 

 clusion seems to be that small larva3 of this and similar 

 species pupating early are almost sure to be males, 



