314 Experimental Zoology 



becomes active again with the return of vegetation, and becomes 

 a chrysalid, emerging after a month in this condition in July or 

 August, when the eggs are laid. If the caterpillars are kept in a 

 warm place in the autumn and during the winter, they hiber- 

 nate nevertheless, although the resting stage, the diapause, may 

 be much affected. If the caterpillars are left outside in the 

 cold for a while and then brought into the warmth, they awake 

 a month sooner than normal, i.e. at the beginning of March, but 

 nevertheless produce their typical moths at the normal time. 

 Caterpillars that are not subjected to cold at all, but are brought 

 into a warm room in the autumn, hibernate only a month, and 

 begin in December their second period of activity preparatory 

 to becoming a chrysalis, which occurs in March or April ; but 

 they do not emerge as moths until after an entire year, thus re- 

 maining chrysalids 13 months instead of only 28 days. The 

 moth is identical with the normal. Thus by shortening the 

 larval life the pupal life is prolonged. 



Changes in food also affect the length of the different stages 

 of development. For example, Ocneria dispar lays its eggs 

 in July, and these do not hatch until the following April; the 

 larval life extends to the middle of June; the pupa condition 

 lasts until the middle of July. This is the normal course. Fed 

 on the leaves of the walnut, the young caterpillars do not reach 

 their complete development until the beginning of July, when 

 they pupate, but the pupal life is correspondingly shortened and 

 lasts only 20 days. Similar changes are affected by other plants 

 that also supply insufficient nourishment. In all of these cases 

 it was found that the larval life is prolonged and the pupal 

 life shortened. The reverse effect is produced by those plants 

 that furnish a better nutriment than the normal. The cater- 

 pillars grow rapidly and pupate 15 days sooner than do 

 those fed on their habitual food plant, but the pupal life is 

 sensibly prolonged. It lasts after Pimprenelle and Esparcette 

 40 days, after dandylion 43 days, instead of the ordinary 28 

 days. " What the insect gains in the larval stage it loses in 

 the pupa stage." 



