ENTOMOLOGY. 89 



Tery difficult to say at what precise point of time 

 he transition from the one to the other takes 

 >lace ; and in such species as are perfectly apterous, 

 such as Cimex Lectularius and many Phasmidse,) 

 a like difficulty may be experienced in distinguishing 

 he pupa from the imago. 



The second division comprises the pupae of all the 

 >rders not enumerated above, and constitutes, there- 

 ore, by far the most extensive of the two. Although 

 hey agree in the general property of being wholly 

 unlike the larvae, and in being incapable of eating and 

 valking, they yet offer not unimportant distinctions 

 among themselves in several particulars. Some have 

 all the limbs encased in separate membranous en- 

 velopes, and therefore lie free, although closely ad- 

 iressed to the body ; others are covered with a hard 

 >kin or horny case, on which the different parts can 

 e traced by their forming projecting lines ; while in 

 ithers the integument is opaque and uniform, con- 

 cealing every thing within it. To the first of these 

 Belong the entire orders Coleoptera and Hymenoptera, 

 as well as certain tribes among the Neuroptera and 

 )iptera. These were called by Linnaeus incomplete 

 mpae, by Lamark mumice coarctatce, and by Bur- 

 tneister pupce exaratce. The second form the obtected 

 )upae of Linnaeus (pupce larvatce, Burm.J and com- 

 >rehend all those of the order Lepidoptera, which are 

 usually known by the term chrysalis. The third sub- 

 division includes the larger proportion of the order 

 Diptera, which were the pupce coosrctatce of Linn., 

 ihe case being nothing more than the dried skin of 



