STATES OF INSECTS. 277 



falls down, and leaves a free passage for its exit. A 

 contrivance almost similar is adopted by a caterpillar 

 which feeds in the interior of the heads of a species of 

 teazel (Dipsacus L.), for a minute and interesting history 

 of which we are indebted to Bonnet. This caterpillar 

 previously to its metamorphosis actually cuts a circular 

 opening in the head, sufficiently large for the egress of the 

 future moth ; but to secure this sally-port during its long 

 sleep, it artfully closes it with fibres of the teazel, closely 

 but not strongly glued together a . Another small cater- 

 pillar described by the same author, resides in the leaf of 

 an ash curiously rolled up into a cone, and then assumes 

 the pupa, which is inclosed in a silken cocoon, ingeni- 

 ously suspended by two threads like a hammock in the 

 middle of its habitation, and of so slight a texture that 

 it presents no obstacle to the extrication of the moth. 

 It is the closely-joined sides of its leafy dwelling that form 

 a barrier, which, were it not for the precaution of the 

 larva, would be impenetrable to so small and weak an 

 animal. The little provident creature, before its change 

 to a pupa, gnaws in the leaf a round opening, taking 

 care not to cut through the exterior epidermis. This 

 door is to serve the moth for its exit, like that formed by 

 the wheat-caterpillar. But in proportion to its bulk its 

 verdant apartment is of considerable size. How then 

 shall the mothk now the exact place where its outlet has 

 been traced ? How, without a clue, shall it discover in 

 its dark abode the precise circle which requires only a 

 push to throw it down ? Even this is foreseen and pro- 

 vided against. Out of twenty positions in which its ham- 



J Bonnet, CEuv. ii. 169. 



