HYBERNATION OF INSECTS. 551 



proved from two considerations : first, That the majority of insects assume 

 the imago, and deposit their eggs in the summer and early part of autumn, 

 when the heat suffices to hatch them in a short period ; and secondly, 

 That the eggs of a very large proportion of insects require, for their due 

 exclusion and the nutriment of the larvae springing from them, conditipns 

 only to be fulfilled in summer, as all those which are laid in young fruits 

 and seeds, in the interior and galls of leaves, in insects that exist only 

 in summer, he. The insects which pass the winter in the egg state are 

 chiefly such as have several broods in the course of the year, the females 

 of the last of which lay eggs that, requiring more heat for their develop- 

 ment than then exists, necessarily remain dormant until the return of 

 spring. 



The situation in which the female insect places her eggs in order to 

 their remaining there through the winter, is always admirably adapted to 

 the degree of cold which they are capable of sustaining ; and to the 

 ensuring a due supply of food for the nascent larvae. Thus, with the 

 former view, Acrida verrucivora and many other insects whose eggs are 

 of a tender consistence, deposit them deep in the earth out of the reach 

 of frost ; and with the latter, Clisiocampa neustria, Lasiocampa castrensis, 

 Hypogymna dispar, and some other moths, departing from the ordinary 

 instinct of their congeners, which teaches them to place their eggs upon 

 the leaves of plants, fix theirs to the stem and branches only. That this 

 variation of procedure has reference to the hybernation of the eggs of 

 these particular species, is abundantly obvious. Insects whose eggs are 

 to be hatched in summer usually fix them slightly to the leaves upon 

 which the larvae are to feed. But it is evident that, were this plan to be 

 adopted by those whose eggs remain through the winter, their progeny 

 might be blown away along with the leaf to which they are attached, far 

 from their destined food. These, therefore, choose a more stable support, 

 and carefully fasten them, as has just been observed, either to the trunk 

 or branches of the tree, whose young leaves in spring are to be the food 

 of the excluded larvae. The latter plan is followed by the female of 

 Clisiocampa neustria, which curiously gums her eggs in bracelets round 

 the twigs of the hawthorn, &.c. But another provision is demanded. 

 Were these eggs of the usual delicate consistence, and to be attached with 

 the ordinary slight gluten, they would have a poor chance of surviving 

 the storms of rain and snow and hail to which for six or eight months they 

 are exposed. They are therefore covered with a shell much more hard 

 and thick than common ; packed as closely as possible to each other ; 

 and the interstices are filled up with a tenacious gum, which soon hardens 

 the whole into a solid mass almost capable of resisting a penknife. Thus 

 secured, they defy the elements, and brave the blasts of winter uninjured. 

 The female of Hypogymna dispar, whose eggs have a more tender shell, 

 glues them in an oval mass to the stem of a tree (whence the German 

 gardeners call the larvae Stamm-raupe), and then covers them with a warm 

 non-conducting coat of hairs plucked from her own body, equally imper- 

 vious to cold and wet. 



Another of those beautiful relations between objects at first sight appa- 

 rently unconnected, which at every step reward the votaries of entomo- 

 logy, is afforded by the coincidence between the period of the hatching 



