540 INSTINCT OF INSECTS. 



others contented themselves with spinning a silken veil before the open- 

 ing. 1 



The larva of the cabbage-butterfly (Pontia Brassicaf), when about to 

 assume the pupa state, commonly fixes itself to the under side of the cop- 

 ing of a wall or some similar projection ; but the ends of the slender 

 thread which serves for its girth would not adhere firmly to stone or brick, 

 or even wood. In such situations, therefore, it previously covers a space 

 of about an inch long and half an inch broad with a web of silk, and to 

 this extensive base its girth can be securely fastened. That this proceed- 

 ing, however, is not the result of a blind unaccommodating instinct seems 

 proved by a fact which has come under my own observation. Having fed 

 some of these larvae in a box covered by a piece of muslin, they attached 

 themselves to this covering ; but as its texture afforded a firm hold to 

 their girth, they span no preparatory web. 



Bombus 2 Muscorum, and some other species of humble-bees, cover their 

 nests with a roof of moss. M. P. Huber having placed a nest of the 

 former under a bell-glass, he stuffed the interstices between its bottom and 

 the irregular surface on which it rested with a linen cloth. This cloth, 

 the bees, finding themselves in a situation where no moss was to be had, 

 tore thread from thread, carded it with their feet into a felted mass, and 

 applied it to the same purpose as moss, for which it was nearly as well 

 adapted. Some other humble-bees tore the cover of a book with which 

 he had closed the top of the box that contained them, and made use of 

 the detached morsels in covering their nest. 8 



The larva of Cossus ligniperda, which feeds in the interior of trees, pre- 

 viously to fabricating a cocoon and assuming the pupa state, forms for the 

 egress of the future moth a cylindrical orifice, except when it finds a suit- 

 able hole ready made. When the moth is about to appear, the chrysalis 

 with its anterior end forces an opening in the cocoon. If the orifice in 

 the tree has been formed by itself, in which case it exactly fits its body, 

 it entirely quits the cocoon, and pushes itself half way out of the hole, 

 where it remains secure from falling until the moth is disclosed. But if 

 the orifice, having been adopted, be larger than it ought to have been, and 

 thus not capable of supporting the pupa in this position, the provident 

 insect pushes itself only halfway out of the cocoon, which thus serves for 

 the support which in the former case the wood itself afforded. 4 



The variations in the procedures of the larva of a little moth described 

 by Reaumur, whose habitation has been before noticed one of those 

 which constantly reside in a sub-cylindrical case are still more remarkable. 

 This little caterpillar feeds upon the elm, the leaves of which serve it at 

 once for food and clothing. It eats the parenchyma or inner pulp, bur- 

 rowing between the upper and under membranes ; of portions of which 

 cut out, and properly sewed together, it forms its case. Its usual plan is 

 to insinuate itself between the epidermal membranes of the leaf, close to 

 one of the edges. Parallel with this it excavates a cavity of suitable form 

 and dimensions, gnawing the pulp even out of every projection of the 

 serratures, but carefully avoiding to separate the membranes at the very 

 edge, which with a wise saving of labour it intends should form one of the 



1 (Euvres, ii. 238. See above, p. 211. 3 Apis, * *. e. 2. K. 



8 Linn. Trans, vi. 254. * Lyonet, Traite Anatomiyue t &c. 16> 



