THE CATERPILLAR KIND. 167 



many occasions, seen to cast forth the internal coat of their in- 

 testines with their food, in the changes which they so frequently 

 undergo. But the intestines take up but a small part of the ani 

 mars body, if compared to the fatty substance in which they are 

 involved. This substance changes its colour when the insect's 

 metamorphosis begins to approach ; and from white it is usually 

 seen to become yellow. If to these parts we add the caterpillar's 

 implements for spinning (for all caterpillars spin at one time 

 or another,) we shall have a rude sketch of this animal's con- 

 formation. 



The life of a caterpillar seems one continued succession of 

 changes ; and it is seen to throw off one skin only to assume 

 another ; which also is divested in its turn : and thus for eight 

 or ten times successively. We must not, however, confound this 

 changing of the skin with the great metamorphosis which it is 

 afterwards to undergo. The throwing off one skin and assum- 

 ing another, seems, in comparison, but a slight operation among 

 these animals ; this is but the work of a day, the other is the 

 great adventure of their lives. Indeed, this faculty of changing 

 the skin is not peculiar to caterpillars only, but is common to all 

 the insect kind, and even to some animals that claim a higher 

 rank in nature. We have already seen the lobster and the crab 

 outgrowing their first shells, and then bursting from their con- 

 finement, in order to assume a covering more roomy and conve- 

 nient. It is probable that the louse, the flea, and the spider, 

 change their covering from the same necessity ; and growing 

 too large for the crust in which they have been for some time 

 inclosed, burst it for another. This period is probably that 

 of their growth ; for as soon as their new skin is hardened round 

 them, the animal's growth is necessarily circumscribed while it 

 remains within it. With respect to caterpillars, many of them 

 change their skins five or six times in a season ; and this cover- 

 ing when cast off, often seems so complete, that many might 

 mistake the empty skin for the real insect. Among the hairy 

 caterpillars, for instance, the cast skin is covered with hair; the 

 feet, as well gristly as membranous, remain fixed to it ; even the 

 parts which nothing but a microscope can discover are visible in 

 it : in short, all the parts of the head, not only the skull, but the 

 teeth. 



In proportion as the time approaches in which the caterpillar 

 is to cast its old skin, its colours become more feeble, the skin 

 seems to wither and grow dry, and in some measure resembles 

 a leaf when it is no longer supplied with moisture from the 

 stock. At that time the insect begins to iind itself under a 

 necessity of changing; and it is not effected without violent 

 labour, and perhaps pain. A day or two before the critical 



