244 STATES OF INSECTS. (Pupa.) 
the last skin of the larvee with this hard covering. At 
the moment of this change the envelope is nearly as soft 
and membranous as in the order first mentioned. But 
they are besides covered with a viscous fluid, which ap- 
pears to ooze out, chiefly from under the wings, and 
which very soon drying, forms the exterior hard shell *. 
At first the antenn, wings, and legs, like those of Coleo- 
ptera and Hymenoptera, can be each separated from the 
body; and it is only after these parts have been glued to- 
gether by the fluid just mentioned, which takes place in 
less than twenty-four hours>, that they are immoveably 
attached to the body of the pupa, as we usually see them. 
In fact, the essential difference between incomplete and 
obtected pupae seems to be, that in the former the limbs 
and body are only covered each with a single membranous 
integument, whereas in the latter they are besides glued 
together by a substance which forms an additional and 
harder envelope. It is not easy to explain the alteration 
that takes place in the texture of the skin of such dipte-- 
vous pup as retain the skin of the larva. In the latter 
this is generally a transparent and very fine membrane : 
yet the very same integument becomes to the pupa an 
opaque and rigid case. 
The surface of the skin of the greater number of pupze 
is smooth, but in those of many Papilionide it is rugose 
and warty: this you may see, particularly in that of Pa- 
pilio Machaon. In many of the hawk-moths it is covered 
with impressed puncta. In Aglia Jo the upper side of 
the channels that separate the intermediate segments of 
the abdomen are curiously striated with transverse striz, 
* Reaum, i. 355. » N. Dict. d’ Hist. Nat, ubi sup. 59. 
