HYBERNATION OF INSECTS. 521 



other than a slight covering ; while the more tender species either enter 

 the earth beyond the reach of frost, or prepare for themselves artificial 

 cavities in substances, such as moss and rotten wood, which conduct heat 

 with difficulty, and defend them from an injuriously low temperature. It 

 does not appear that any perfect insect has the faculty of fabricating for 

 itself a winter abode similar to those formed of silk, &c., by some larvae. 

 Schmid, indeed, has mentioned finding Rhagium mordax and Inquisitor in 

 such abodes, constructed, as he thought, of the inner bark of trees ; but 

 these, as Illiger has suggested, were more probably the deserted dwellings 

 of lepidopterous larvae, of which the beetles in question had taken posses- 

 sion. 1 Most insects place themselves in their hybernacula in the attitude 

 which they ordinarily assume when at rest ; but others choose a position 

 peculiar to their winter abode. So most of the ground beetles (Eu- 

 trechina) adhere by their claws to the under side of the stone which serves 

 for their retreat, their backs being next to the ground ; in which posture, 

 probably, they are most effectually protected from wet. Gyrohypnus san- 

 guinolentus, and other rove-beetles of the same genus, coils itself up like a 

 snake, with the head in the centre. 



The majority of insects pass the winter in perfect solitude. Occasion- 

 ally, however, several individuals of one species, not merely of such insects 

 as Anchomenus prasinus, a beetle, Pyrrhocoris apterus, a bug, &c., which 

 usually in summer also live in a sort of society, but of others which are 

 never seen thus to associate, as Haltica oleracea, Carabus intricatus, and 

 several Coccincll<z, &c., are found crowded together. This is perhaps often 

 more through accident than design, as individuals of the same species are 

 frequently met with singly ; yet that it is not wholly accidental seems 

 proved by the fact that such assemblages are generally of the same genus 

 and even species. Sometimes, however, insects of dissimilar genera and 

 even orders are met with together. Schmid once in February found the 

 rare Lomechusa strumosa torpid in an ant-hill, in the midst of a conglome- 

 rated lump of ants, with which it was closely intertwined. 2 



By far the greater proportion of insects pass the winter only in one or 

 other of the several states of egg, pupa, larva, or imago, but are never 

 found to hybernate in more than one. Some species, however, depart 

 from this rule. Thus Aphis Rosa, Cardui, and probably many others of 

 the genus, hybernate both in the egg and perfect state 3 ; Cynthia Cardui, 

 Gonepteryx Rhamni, and some other species, usually in the pupa, but often 

 in the perfect state also ; and Vanessa Io, according to the accurate Brahm, 

 in the three states of egg, pupa, and imago. 4 It is probable that in these 

 instances the perfect insects are females, which, not having been impreg- 

 nated, have their term of life prolonged beyond the ordinary period. 



The first cold weather, after insects have entered their winter quarters, 

 produces effects upon them similar to those which occur in the dormouse, 

 hedgehog, and others of the larger animals subject to torpor. At first a 

 partial benumbment takes place ; but the insect, if touched, is still capable 

 of moving its organs. But as the cold increases all the animal functions 

 cease. The insect breathes no longer, and has no need of a supply of air 5 ; 

 its nutritive secretions cease ; no more food is required ; and it has all the 



i Illig. Mag. i. 216. 8 Ibid. i. 491. 



3 Kyber in Germar, Magazin der Entomologie, ii. 2. 



4 Ins. Kal. ii. 188. * Spallanzani, Rapports de I' Air, &c., i. 30. 



