348 INSECTA. 



of the wings, which are totally wanting. The nymph only differs 

 from the larva in possessing stumps or rudiments of wings, which 

 are developed at its final change of tegument, and render the animal 

 perfect. Such are the Cimices, Grylli, &,c. , Finally, the remain- 

 ing Insects provided with wings that are said to undergo a complete 

 metamorphosis, are at first larvce, resembling caterpillars or Worms, 

 and then become motionless nymphs, but presenting in that state all 

 the parts of the perfect insect contracted, and as if wrapped in a 

 bandage. 



Tn the nymph of the Coleoptera, Neuroptera, Hymenoptera, &c., 

 these parts, though closely approximated and in contact with the 

 body, are free; but they are not so in that of the Lepidoptera and of 

 many Diptera. An elastic or solid skin is moulded over the body 

 and its external parts, forming a kind of case for it. 



That of the chrysalides of the Lepidoptera merely consisting of a 

 simple pellicle applied to the external organs, following their con- 

 tour in every direction, and forming, for each of them, so many 

 moulds, like the envelope of a mummy, allows us to recognize and 

 distinguish them; but those of Flies and Syrphi, formed of the dried 

 skin of the larva, resemble an egg-like shell. It is a species of cap- 

 sule or case in which the animal is shut up. 



Many larvae, before they pass into their pupa state, prepare a co- 

 coon in which they enclose themselves, either with silk which they 

 draw from the interior of their bodies by means of the spinning ap- 

 paratus of their lip, or other materials which they collect. The 

 perfect Insect issues from the nymph through a fissure or slit which 

 opens on the back of the thorax. In the pupae of Flies one of the 

 extremities is detached, like a cap, to allow the egress of the 

 animal. 



The larvae and pupae of those Insects which experience a semi- 

 metamorphosis only differ from the same in a perfect state, in thte 

 absence of wings. The other external organs are precisely alike. 

 But in such as undergo a complete metamorphosis, the form of the 

 body of the larva has no constant relation with that it is to possess 

 in its perfect state. It is usually more elongated; the head is fre- 

 quently very different, as well in its consistence as in its figure, hav- 

 ing mere rudiments of antennae or perhaps none at all; there are 

 never any compound eyes. 



There is also a great disparity in the organs of manducation, as 



