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, 7.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.” 
