experiments on some Ijepidoptera. 133 



red for several days, and hatching in from 11 to 13 days 

 after removal from the ice. These are strong examples 

 of individual character manifested at a very early age. 

 The eggs seemed in all cases uninjured by a temperature 

 of 80° — 90°, their development being accelerated by it. 



Larval Stage, growing Larv^. — (1) Exposure to low 

 temperature. — Larvae of illustraria in their first skins not 

 exceeding 6 days in age were iced, and all were dead in 

 20 days ; some 30 of the same age, which were cooled, 

 scarcely seemed to grow, but two lived rather more than 

 63 days. Some that were iced in their second skins 

 were all dead in 21 days. Some that were cooled in one 

 or other of their two last skins grew slowly, four of 

 them spun-up, one as late as the 58th day, and two 

 pupated. In all the cases of cooling the larvae were 

 supplied with food, which was slowly eaten ; in the case 

 of the iced larvffi food did not seem necessary. The 

 experiments seem to indicate that the older larva is 

 more capable of enduring a low temperature than is 

 either the egg or the young larva, and as illustraria will 

 live and apparently thrive, at least for a time, on dead 

 leaves, it would seem that this species might hibernate 

 as a larva in countries where the winter is a short one. 



(2) Exposure to a high temperature. — Illunaria, illus- 

 traria, autumnaria (the old alniaria), and alniaria (the 

 old tiliaria), will all bear a continuous temperature of 

 80°, or a little more, apparently without injury ; but 

 one of 90° to 100° is very injurious to them. 



Larv.e and pup^e ; effect of the temperature to 



WHICH they are subjected ON THE COLOUR OF THE MoTH. 



— The series of autumnaria exhibited to the Society last 

 year indicated that temperature in the earlier stages 

 materially afiected the colouring and markings of the 

 perfect insect, but left it uncertain whether that effect 

 was produced in the larval or in the pupal stage. As 

 then remarked, they seemed to show either that the 

 larval period was the critical one, or that the colour of 

 the perfect insect could be modified by exposing the 

 pupa to very moderate differences of temperature. I 

 determined this year, so far as possible, to clear up the 

 point, and accordingly tried the systematic experiments 

 I am about to describe. At the suggestion of Dr. Chap- 

 man, to whom I am indebted for a supply of eggs of 

 both species, I experimented both with autumnaria, as a 



