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LETTER XXVI. 



ON THE HYBERNATION OF INSECTS. 



If insects can boast of enjoying a greater variety of food than many other 

 tribes of animals, this advantage seems at first sight more than counter- 

 balanced in our climates by the temporary nature of their supply. The 

 graminivorous quadrupeds, with few exceptions, however scanty their bill 

 of fare, and their carnivorous brethren, as well as the whole race of birds 

 and fishes, can at all seasons satisfy, in greater or less abundance, their 

 demand for food. But to the great majority of insects, the earth for nearly 

 one half of the year is a barren desert, affording no appropriate nutriment. 

 As soon as winter has stripped the vegetable world of its foliage, the vast 

 hosts of insects that feed on the leaves of plants must necessarily fast 

 until the return of spring : and even the carniv^orous tribes, such as the 

 predaceous beetles, parasitic Hi/menoptera, Sphecina, &-c., would at that 

 period of the year in vain look for their accustomed prey. 



How is this difficulty provided for ? In what mode has the Universal 

 Parent secured an uninterrupted succession of generations in a class of 

 animals for the most part doomed to a six months' deprivation of the food 

 whicii they ordinarily devour with such voracity ? By a beautiful series 

 of provisions founded on the faculty, common also to some of the larger 

 animals, of passing the winter in a state of torpor — by ordaining that the 

 insect shall live through that period, either in an incomplete state of its 

 existence when its organs of nutrition are undeveloped, or, if the active 

 epoch of its life has commenced, that it shall seek out appropriate hyher- 

 nacula, or winter quarters, and in them fall into a profound sleep, during 

 which a supply of food is equally unnecessary. 



In two of the four states of existence common to insects, in which 

 different tribes pass the winter, namely, the egg and the pupa state, the 

 organs for taking food (except in some cases in the latter) are not 

 developed, and consequently the animal is incapable of eating. The 

 existence of insects in these states during the winter differs from their 

 existence in the same form in summer only in the greater length of its 

 term. In both seasons food is alike unnecessary, so that their hybernation 

 in these circumstances has little or nothing analogous to that of larger 

 animals. With this, however, strictly accords their hybernation in the 

 larva and imago states, in which their abstinence from food is solely owing 

 to the torpor that pervades them, and the consequent non-expenditure of 

 the vital powers. — I shall attend to the peculiarities of their hybernation 

 in each of these states in the order just laid down ; premising that we 

 have yet much to learn on this subject, no observations having been 

 instituted respecting the state in which multitudes of insects pass the 

 winter. 



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

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



