INSECTS IN GENERAL. 81 



In proportion as the larvae increase, they change their skin. 

 This may be termed their moulting, and one envelope is often 

 succeeded by another of a totally different colour. The time 

 of moulting is a serious crisis for the larvae, and its periods 

 are hastened or retarded, according to the elevation or de- 

 pression of temperature, the abundance or deficiency of nutri- 

 ment. In the larva state, insects are engaged only in their 

 preservation and growth. 



The nymphs, or pupae, to which other names have been 

 given, according to the differences which the species of the 

 various orders, established in the insect class, present in their 

 forms, are individuals passing from the larva state to that of 

 the perfect insect or imago. Under this form, the animal's 

 growth usually ceases. It may still sometimes take nutri- 

 ment, but it participates much of the form which it is to 

 assume in the sequel. It exhibits as it were the outline, or 

 rough sketch with all its parts, but most generally crowded 

 together, and as it were, swaddled up. Those pupae which 

 can feed themselves, are, as might be supposed, more or less 

 agile, and pretty nearly conformed in the same manner as 

 the perfect insect. The majority resemble the larvae, with 

 this difference, that they very frequently exhibit the rudi- 

 ments of wings. Such is the case with all the orthoptera, 

 and in particular with the locusts. It is also the case with 

 all the hemiptera, as the cigalae, &c. Similar dispositions 

 are observable in some neuroptera, as the ephemera, and the 

 libellulae ; but in that order there are other species, such as 

 the antlions, the hemerobiae, Sec, which proceed from nymphs 

 altogether different from the larvae. 



It is chiefly according to the modifications which insects 

 undergo at the period when they assume this form of nymphs, 

 that the various modes of their metamorphoses have received 

 their different denominations. Some of these denominations 

 are any thing but happy, yet still it is not perhaps very 



VOL. XIV. a 



