CH. III.J INSECTS WHICH FORM COCOONS 73 



fore refer the extrication to the effect of some 

 liquid with which the insect is furnished, sufficient 

 to dissolve the gummy matter of its cocoon. This 

 liquid Reaumur ascertained by experiment was 

 neitlier of an aqueous nor an inflammable nature, like 

 spirits of wine. Messrs. Kirby and Spence con- 

 sider that it must essentially be of an acid nature, 

 so powerful as immediately to dissolve the gum, 

 and yet so harmless to the moth as not to injure it 

 by its action, a supposition which may be consid- 

 ered analogous to the action of the gastric juice. 

 This caterpillar, notwithstanding its remarkable 

 shape, and the singular fork at the extremity of its 

 body, is unable to guard itself from the attacks of 

 the ichneumon flies. One of these {Ophion luteum) 

 attacks it, and deposites her eggs in its body, in 

 which the grubs of the ichneumons feed in the 

 manner stated in our former volume, a fact recorded 

 by every naturalist since the days of Gcedart. Wc 

 notice this circumstance, because it has been stated 

 in a popular work (Insect Architecture, p. 95, 325) 

 that the ichneumon fly contrives to deposite its eggs 

 in the case of the puss moth ; but no instance has 

 ever yet been recorded of such a fact. When we 

 consider how difficult a thing it must be even for 

 this large moth to efl'ect its escape through the walls 

 of its cocoon, how much more so must it be for its 

 delicately-formed parasites, which have not only to 

 bore through it, but their own individual cocoons 

 also which are enclosed within it. It is true that 

 they are furnished with jaws, but may they not like- 

 wise be provided with some fluid analogous to that 

 of the moth 1 It is remarkable that occasionally 

 several of these parasites, of which four or five 

 prey upon a single caterpillar, are found dead in 

 their cocoons, while one or two only have contrived 

 to escape. This we should consider a sufficient rea- 

 son for doubting the supposition that these parasite 

 grubs, knowing that it would require all the 'united 

 Vol. II.— G 



