4<32 HYBERNATION OF INSECTS. 



and the larvae of Pieris Cratccgi inclose themselves in 

 autumn in cases of the same material % and thus pass the 

 cold season in small societies of from two to twelve, under 

 a common covering formed of leaves. Bonnet mentions 

 a trait of the cleanliness of these insects which is almost 

 ludicrous. He observed in one of these nests a sort of 

 sack containing nothing but grains of excrement ; and 

 a friend assured him that he had seen one of these cater- 

 pillars partly protrude itself out of its case, the hind feet 

 first, to eject a similar grain ; so that it would seem the 

 society have on their establishment a scavenger, whose 

 business it is to sweep the streets and convey the rejec- 

 tamenta to one grand repository 5 ! This, however 

 singular, is rendered not improbable from the fact that 

 beavers dig in their habitations holes solely destined for 

 a like purpose . 



A very considerable number of insects hybernate in the 

 perfect state, chiefly of the orders Coleoptcra, Hemiptera, 

 Hymenoptera, and Diptera, and especially of the first. 

 Vanessa Urticae^ lo, and a few other lepidopterous spe- 

 cies, with a small proportion of the other orders, occa- 

 sionally survive the winter ; but the bulk of these are 

 rarely found to hybernate as perfect insects. Of cole- 



a I have reason to think that the larvae of some species of Heme- 

 robius thus protect themselves by a net-like case of silken threads ; 

 at least I found one to-day (December 3d, 1816) inclosed in a case 

 of this description concealed under the bark of a tree: and it is not 

 very likely that it could be a cocoon, both because the inhabitant 

 was not a pupa, which state, according to Reaumur, is assumed soon 

 after the cocoon is fabricated (iii. 385) ; and because the same author 

 describes the cocoons of these insects as perfectly spherical andofa 

 very close texture (384) ; while this was oblong, and the net-work 

 with rather wide meshes. 



b GEuv. ii. 72. c Ibid ix. 167. 



