MOTIONS OF INSrX'TS. 297 



therefore consider pupa? as of two kinds — aclive pupaj 

 and quiescent piipas. 



The motions of most insects whose pupaB are active^ 

 are so similar in all their states, except where the 

 wings are concerned, as not to need any separate ac- 

 count. I shall tlierefore request you to wait for what 

 I have to say upon them, till I enter upon those of (lie 

 imago. One insect, however, of this kind, moving dif- 

 ferently in its preparatory states, is entitled to notice 

 under the present head. — In a late letter, 1 mentioned 

 to you a bug (Rcduvius persomdus, F.) which usually 

 covers itself with a mask of dust, and fragments of 

 various kinds, cutting a very grotesque figured Its 

 awkward motions add not Ji little to the effect of its 

 appearance. When so disposed, it can move as well 

 and as fast as its congeners ; yet this does not usually 

 answer its purpose, which is to assume tlie appearance 

 of an inanimate substance. It tlierefore hitciies alono: 

 in the most leisurely manner possible, as if it was 

 counting its steps. Having set one foot forward (for 

 it moves only one leg at a time), it stops a little before 

 it brings up its fellow^, and so on Avith the second and 

 third legs. It moves its antennaj in a similar y/ay, 

 striking, as it were, first with one, and then, after an 

 interval of repose, with the other"*. — The pups of gnats 

 also, as v»^ell as those of many other aquatic Diptera, 

 retain their locomotive powers, not however the free 

 motion of their limbs. When not engaged in action, 

 they ascend to the surface by the natural levity of their 

 bodies, and are there suspended by two auriform re- 

 spiratory organs in the anterior part of the trunk, 



^ See above, p. 259. " Dc Geer, iii. 2S4. 



