ENTOMOLOGY. 
89 
very difficult to say at what precise point of time 
the transition from the one to the other talces 
place ; and in such species as are perfectly apterous, 
(such as Cimex Lectularius and many Phasmid®,) 
a like difficulty may be experienced in distinguishing 
the pupa from the imago. 
The second division comprises the pup® of all the 
orders not enumerated above, and constitutes, there- 
fore, by far the most extensive of the two. Although 
they agree in the general property of being wholly 
unlike the larvae, and in being incapable of eating and 
walking, 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- 
pressed to the body ; others are covered with a hard 
skin or horny case, on which the different parts can 
be traced by their forming projecting lines ; while in 
others 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 
Diptera. These were called by Linn® us incomplete 
pup®, by Lamark mumice coarctatce , and by Bur- 
meister pupce exaratce. The second form the obtected 
pup® of Linn® us ( pupce larvatce , Bunn.) and com- 
prehend 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 coarctatce of Linn., 
the case being nothing more than the dried skin of 
