MOTIONS OF INSECTS. 293 



little water. You will find that, while the animal moves 

 forward, a current of water is produced by this pump- 

 ing, in a contrary direction. As the larva, between 

 every stroke of its internal piston, has to draw in a fresh 

 supply of water, an interval must of course take place 

 between the strokes. Sometimes it will lift its anus out 

 of the water, when a long thread of water, if I may so 

 speak, issues from it*. 



II. I am next to say something upon the motions of 

 insects in their pupa state. This is usually to our little 

 favourites a state of perfect repose ; but, as I long since 

 observed 5 , there are several that, even when become 

 pupae, are as active and feed as rapaciously as they do 

 when they are either larvae or perfect insects. The 

 Dermaptera, Orthoptera, Hemiptera, many of the Neu- 

 roptcra, and the majority of the Aptera, are of this de- 

 scription. With respect to their motions, we may 

 therefore consider pupae as of two kinds active pupae, 

 and quiescent pupae. 



The motions of most insects whose pupae are active, 

 are so similar in all their states, except where the wings 

 are concerned, as not to need any separate account. I 

 shall therefore request you to wait for what I have to 

 say upon them, till I enter upon those of the imago. 

 One insect, however, of this kind, moving differently in 

 its preparatory states, is entitled to notice under the pre- 

 sent head. In a late letter, I mentioned to you a bug 

 (Reduvius personatus) which usually covers itself with a 

 mask of dust, and fragments of various kinds, cutting a 



3 De Geer, ii. 675 Compare Reaum. vi. 393. 

 b VOL. I, 66. 



