324 INSECT TRANSFORMATIONS. 



to the shell of the chrysalis, and to loosen the folds 

 of the abdomen. In taking this exercise, it can 

 only move the abdomen in various directions ; as 

 one side of the rings is moved forward, the hooks in 

 the serrated lines take hold of the silk and prevent 

 their sliding back ; the next flexure brings forward 

 the opposite side of the rings, which are prevented 

 by the points on that side from slipping back in the 

 same manner, and the chrysalis is forced out of the 

 slightly-woven extremity of the cocoon, and through 

 the silk-lined cavity, till it is protruded for about one- 

 third of its length out of the opening in the bark and 

 into the air."* 



A no less ingenious contrivance for escape was 

 observed by Bonnet in one of the leaf-rollers, which 

 feeds on the leaves of young ash-trees. It rolls up the 

 leaf into a cone, and is transformed into a small pupa, 

 resembling a grain of oats. The chamber w^hich it 

 forms is not only extensive in proportion to the size 

 of the insect, but is so very compact, that it does not 

 appear in what manner it is to effect its escape. 

 Within the capacious chamber of the leaf it hangs 

 itself up by two lines, after the manner of a sailor's 

 hammock. But, previous to this, it gnaws a cir- 

 cular piece half through the leaf, taking care not to 

 injure the exterior membrane. In order to render 

 this little door easy to be found, the caterpillar, as if 

 foreseeing that the blind pupa could not otherwise 

 discover it, fixes one of the suspensory threads near 

 its margin, guided by which the insect makes its 

 exit with the utmost ease, for the head is uniformly 

 swung up by the door thread.f 



A very similar proceeding is recorded of the mi 

 nute granary-moth {Tinea granelld), which we 

 have before mentioned as destructive to grain. The 



* Peck, quoted by Kirby and Spence. 

 f Bonnet, CEuvres, vol. ii. p. 207. 



