HYBERNATION OF INSECTS. 517 



It is probable that some insects of almost every order hibernate in the 

 egg state ; though that these must be comparatively few in number, seems 

 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, conditions 

 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, &c. 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 development 

 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 con- 

 sistence, 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 con- 

 geners, 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 pro- 

 vision 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 gar T 

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

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

 to cold and wet. 



Another of those beautiful relations between objects at first sight 

 apparently unconnected, which at every step reward the votaries of En- 

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

 in spring of eggs deposited before winter, and of the leafing of the trees 

 upon which they have been fixed, and on whose foliage the larvae are to 



LL 3 



