CHEMICAL SOLVENT. 287 



feeble insect prisoner within is provided with 

 a peculiar chemical fluid, of greater powers of 

 solution than are requisite in the last instance. 

 The cocoon of the "pussmoth," in particular, is 

 so hard and dense, as to resist even the point 

 of a penknife; and the insect it holds confined 

 within it is a weak creature, totally unprovided 

 with any apparatus fit for penetrating walls so 

 hard and dense as these. What is it to do? 

 " Here," observe the writers last quoted, " the 

 eyes are clearly incompetent; nor could any 

 ordinary fluid assist their operations, for the gum 

 which unites the woody particles of the cocoon 

 is indissoluble in aqueous menstrua. What an 

 aqueous solvent cannot effect, an acid is competent 

 to ; and with a bag of such acid our moth is fur- 

 nished. The contents of this she pours out as 

 soon as she has forced her head through the skin 

 of the pupa, and upon the opposite end of the 

 cocoon. The acid instantly acts upon the gum, 

 loosens the cohesion of the grains of wood, and 

 a very gentle effort suffices to break down what 

 was, a minute ago, a strong barrier. How ad- 

 mirable and effectual a provision ! But there 

 is yet another marvel connected with it. Ask 



