STATES Of JNSECTS. 245 



the last skin of the larvae 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 a . 

 At first the antennae, wings, and legs, like those of Coleo- 

 ptera and Hymenoplera, 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 b , 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- 

 rous pupae 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 pupae 

 is smooth, but in those of many Papilionidce it is rugose 

 and warty : this you may see, particularly in that of Pa~ 

 pilio Machaon. In many of the hawkmoths (Sphinx L.) 

 it is covered with impressed puncta. In Attacus Io the 

 upper side of the channels that separate the intermediate 

 segments of the abdomen are curiously striated with trans- 



' Reaum, i. 355. h N. Diet. a" Hist. Nat. ubi sup. 59. 



