STATES OF INSECTS. 283 



moistened end is probably sufficient : and hence we find 

 in so many newly disclosed moths the hair in that part 

 wet, and closely pressed down a . If it be apparently 

 difficult for the silkworm-moth to effect an opening in its 

 cocoon, how much harder must seem the task of the 

 puss-moth (Centra Vinula) to pierce the solid walls of its 

 wood- thickened case? Here the eyes are clearly incom- 

 petent ; nor could any ordinary fluid assist their opera- 

 tion, for the gum which unites the ligneous particles is 

 indissoluble in aqueous menstrua. You begin to tremble 

 for the fate of the moth incarcerated in such an imper- 

 vious dungeon — but without cause : what an aqueous sol- 

 vent cannot effect, an acid is competent to ; and with a 

 bag of such acid our moth is furnished. The contents of 

 this she pours out as soon as she has forced her head 

 through the skin of the chrysalis, and upon the opposite 

 end of the cocoon. The acid instantly acts upon the 

 gum, loosens the cohesiozi of the grains of wood, and a 

 very gentle effort suffices to push down what was a mi- 

 nute ago so strong a barrier. How admirable and effec- 

 tual a provision ! But there is yet another marvel con- 

 nected with it. Ask a chemist, of what materials a vessel 

 ought to be to contain so potent an acid : he will reply, 

 — of glass. Yet our moth has no glass recipient: her 

 bottle is a membranous bag ; but of so wonderful a fabric 

 as not to be acted upon by a menstruum which a gum, 

 apparently of a resinous nature, is unable to resist ! This 

 fact can only be explained by the analogous insensibi- 

 lity of the stomach to the gastric juice, which in some 

 animals can dissolve bone, — and it is equally worthy of 



* Pczold. 171, 



