MOULTING OF GRUBS. 177 



grow dry and shrivelled, and the stature grows shorter 

 and more diminutive. Even in youth similar changes 

 are in progress, a system of absorbent vessels being 

 provided for removing' worn materials from all parts 

 of the body, and carrying at least one portion of these 

 along with the blood into the lungs, whence it goes 

 off in minute particles with the breath. No similar 

 process of removing worn materials has, so far as we 

 know, been discovered in caterpillars ; and it is, 

 indeed, improbable, as the successive changes of the 

 skin accomplish all that is wanted in this respect. 

 That the worn materials, however, of the cast skins 

 are not altogether useless, appears from the singular 

 circumstance of the new-clothed caterpillar often 

 devouring them, as that of the hawthorn-butterfly 

 {Pieris Cratcegi^ Stephens) does the shell of the 

 egg it has just been hatched from*. It may be 

 remarked, that it is chiefly the larger caterpillars of 

 the puss and some of the hawk-moths which have 

 been observed to eat their skins ; none of the spinous 

 or hairy ones seem to relish this strange sort of food. 

 In the case of the warty-eft {Triton palustris, 

 Flem.), which frequently casts its outer skin, we 

 have observed that it is frequently eaten by the animal 

 itselff. 



The grubs of some two-winged flies {Muscidce)^ 

 and of wasps, bees, ants, and ichneumon-flies, do 

 not change their skins like the larva? we have just 

 been considering; but spiders and other allied tribes 

 {Arach?iid(E), though they exhibit no other appear- 

 ance of larvae, moult frequently during their growth. 

 Goldsmith, amongst other curious mistatements re- 

 specting a house-spider which he himself observed, 

 asserts that it " lived three years, every year it 

 changed its skin, and got a new set of legs : I 

 have sometimes plucked otf a limb, which grew 

 * Bonnet, (Euvies, vol. ii. p, 18. f .).R, 



