CECOXOMY OF INSECTS. 41 



presses the body like a wedge into this opening, by which means it is 

 soon torn down from the first to the fourth ring : this renders it large 

 enough for the caterpillar to pass through. 



The caterpillar generally fasts a whole day after each moulting ; for 

 it is necessary that the parts should acquire a certain degree of con- 

 sistency before its organs can perform their ordinary functions. Many 

 perish under this operation. The caterpillar always appears much 

 larger after it has quitted the exuviee than before; for the body had 

 grown under the old skin till it had become too large for it, and the 

 parts being soft they were much compressed; but as soon as this skin is 

 cast oft', the parts distend, and with them the new skin, which is yet of 

 a flexible and tender texture, so that their increase in size at each 

 moulting is considerable. Some caterpillars in changing their skin alter 

 very much in colour and ap[)earance; sometimes the skin from being 

 smooth becomes covered with hair, spines, or tubercles ; and others that 

 are in one stage hairy, have the skin smooth in the next. No sex is de- 

 veloped in the caterpillar state. 



Of the PUPA state. By this term, as understood in the very exten- 

 sive sense Linne proposes, is signified that state of an insect which suc- 

 ceeds the larva, without any regard to the particular appearance it as- 

 sumes in this stage of transformation. From this latitude of meaning it 

 includes therefore, with equal precision and no less propriety, states of 

 the most discordant character. It alike imi)lies the uncouth grub in- 

 cased in its shelly repository and immured in the earth, sluggish, al- 

 most destitiite of motion or the appearance of any animal function, 

 with the lively half-winged locust, or the Cicada, animals sporting in 

 the full enjoyment of life. The hot imprisoned in its oval covering, 

 M ithout the least external sign of animation, is termed a pupa. The 

 moth, quiescent and absent for months, concealed in its shelly cover- 

 ing in the earth, or suspended aloft in its silky envelope to the branch 

 of a tree, is a pupa; and we denominate those pHyja- also which have 

 the vv-ings only hah' expanded ; though, like the nimble-footed Cimex, 

 they are perpetually roving, and deriving sustenance from the blood of 

 other animals; and so also the restless Libe/lulu, which is continually 

 traversing the watery element with the facility of fishes in search of 

 prej'. Modern writers have therefore considered this state as essential 

 in the formation of Orders, and have even laid down certain rules, 

 which taken in conjunction with the characters of the perfect insect, 

 are otten of great use in ascertaining the order to which any genus be- 

 longs. In my account of the Larval have given that of the lepido- 

 pterous order, and shall therefore describe - he Pupa of the same. 



The length of time an insect remains in this form varies much in dif- 

 ferent species. As soon as the inclosed animal acquires sufficient strength 

 to break the bonds of its coufineraent, it makes a powerful eftbrt to escape. 



