68 THE VICTORIAN NATURALIST. 



what Kirby and Spence say on the subject. Here is the passage: — 

 " I am next to give you some account of the second mode in 

 which the release of the perfect insect from its cocoon is effected 

 — that, namely, wherein its own exertions chiefly accomplish the 

 work. The texture of the cocoon of the silkworm moth is 

 uniform in every part, and the layers of silk are equally thick at 

 both ends. The moth makes its way out by cutting or breaking 

 these threads at the end opposite to its head. The question is, 

 what instruments does the moth employ to effect this ? Malpighi 

 asserts that the animal first wets the silk with a liquid calculated 

 to dissolve the gum that connects the threads, and then employs 

 its lengthened head to push them aside and make an opening. 

 But, as Reaumur has observed, we find the threads not merely 

 pushed to each side but actually cut asunder. He therefore 

 infers that the eyes, which are the only hard organs of the head, 

 are the instruments by which the threads are divided, their 

 numerous minute facets serving the purpose of a fine file. 

 Reaumur's correctness cannot be suspected, and he affirms that 

 from observation there can scarcely be a doubt that most of the 

 threads are broken. We are, however, informed by Dr. Rox- 

 burgh that Attacus paphia, when prepared to assume the imago, 

 discharges from its mouth a large quantity of liquid, with which 

 the upper end of the case is so perfectly softened as to enable the 

 moth to work its way out in a very short space of time — 

 an operation which, he says, is always performed in the night. 

 Perhaps the two opinions may be reconciled by supposing the 

 silkworm first to moisten and then break the threads of its cocoon. 

 In those that are of a slighter texture, a mere push against the 

 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. 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, Dicranula vinula, to pierce the solid walls 

 of its wood-thickened case ? Here the eyes are clearly incompe- 

 tent ; nor could any ordinary fluid assist their operation, for the 

 gum which unites the ligneous particles is indissoluble in aqueous 

 menstrua. You begin to tremble for the fate of the moth incar- 

 cerated in such an impervious dungeon — but without cause : what 

 an aqueous solvent 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 cohesion of the 

 grains of wood, and a very gentle effort suffices to push down 

 what was a minute ago so strong a barrier. How admirable and 

 effectual a provision ! " 



The foregoing somewhat lengthy extract shows the conclusions 



