324 INSECT TRANSFORMATIONS. 



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

 the abdomen. In taking tliis 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 ob- 

 served 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, re- 

 sembling a grain of oats. The chamber which it forms 

 is not only extensive in proportion to the size of the in- 

 sect, but is so very compact, that it does not appear in 

 what manner it is to effect its escape. Within the ca- 

 pacious 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 circular piece half through 

 the leaf, taking care not to injure the exterior mem- 

 brane. 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. t 



A very similar proceeding is recorded of the mi- 

 nute grinary moth {Tinea grcmella), which we 

 have before mentioned as destructive to grain. The 



* Peck, quoted by Kirby and Spence. 

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



