68 METAMORPHOSES. 



I have said that most insects eat no food in the pupa 

 state. This qualification is necessary, because in the 

 metamorphoses of insects, as in all her other opera- 

 tions, nature proceeds by measured steps, and a very 

 considerable number (the tribe of locusts, cockroaches, 

 bugs, spiders, &c.) not only greatly resemble the per- 

 fect insect in form, but are equally capable with it of 

 eating and moving. As these insects, however, cast 

 their skins at stated periods, and undergo changes, 

 though slight, in their external and internal conforma- 

 tion, they are regarded also as being subject to meta- 

 morphoses. These piipje may be subdivided into two 

 classes : first, those comprised, with some exceptions, 

 under the Linnean Aptera^ which in almost every re- 

 spect resemble the perfect insect, and were called by 

 Linne complete pupae ; and secondly, those of the Lin- 

 nean order Memiptera, which resemble the perfect in- 

 sect, except in having only the rudiments of wings, and 

 to which the name of semi-complete pupae was applied 

 by Linne, and that of semi-nymphs by some other au- 

 thors^. There is still a fifth kind of pupEP, which are 

 not, as in other instances, excluded from the skin of the 

 larva, but remain concealed under it^ and were hence 

 called by Linne coarctate pupae. These, which are 

 peculiar to flies and some other dipterous genera, may 

 be termed cased-nj/mphs^. 



When, therefore, we employ the tervn pupa, we may 

 refer indifferejitly to the third state of any insect, the 

 particular order being indicated by the context, or an 

 explanatory epithet. The terms chri/salis, (dropping 

 aurelia, which is superfluous), ni/mph, semi-ni/mph, and 



» Plate XVI. Fig. 4. 5. " Plate XVII. Fig. 1—4. 



