262 STATES OF INSECTS. (Pupa.) 
tain maturity, even though larger in bulk, than others 
exposed to a low one:—and this is the fact. ‘The pupa 
of a large moth, which has assumed that state in the 
early part of summer, will often disclose the perfect in- 
sect in twelve or fourteen days; while that of an Ich- 
neumon, not one hundredth part of its size, that did not 
enter this state till late in autumn, will not appear as a 
fly for seven or eight months. But this is not the whole. 
The very same insect, according as it has become a pu- 
pa at an earlier or later period of the year, will at one 
time live but a few weeks, at another several months, in 
that state. Thus, if the caterpillar of Papilio Machaon, 
one of those which has annually a double brood, becomes 
a pupa in July, the butterfly will appear in ¢hzrteen 
days: if not until September, it will not make its ap- 
pearance until the June following; that is, not in less 
than nine or ten months: and the case is the same with 
the pupze of Acronycta Psi, and of a vast number of 
_ other insects. To put beyond all doubt the dependence 
of these remarkable variations on temperature merely, 
it was only necessary that they should be effected, as 
Lister long ago advised*, by artificial means. This 
Reaumur accomplished. In the month of January he 
placed the chrysalises of several moths and butterflies, 
which would not naturally have been disclosed until the 
following May, in a hothouse: the result was, that the 
perfect insects made their appearance in less than a fort- 
night, in the very depth of winter; and by other nume- 
rous and varied experiments he ascertained, that in this 
heated atmosphere five or six days hastened their ma- 
turity more than as many weeks would have done in the 
4 Lister’s Goedart. 122. 
