338 



Aquatic Societies 



Here belong the hosts of minute spring-tails that gathe: 

 in the edges in sheltered places, often in such number: 

 as to blacken the surface as with deposits of soot. 

 Minute as these are they are readily recognized b> 

 their habits of making relatively enormous leaps from 

 place to place. 



(2). Those that lie prone upon the surface. Besi 

 known of these because everywhere conspicuous on stil] 



Fig. 198. Two fallen stems enveloped with a rich growth 

 of the alga, Chcetophora incrassata. 



waters, are the whirl-i-gig beetles. Less common and 

 much less conspicuous are the pupae of the soldier-flies 

 (Stratiomyia, etc.) and the larvae of the Dixa midges. 



(3). Those that hang as if suspended at the surface, 

 with only that part of the body that has^to do with 

 intake of air breaking through the surface film. Here 

 belong by far the larger number of aquatic insects. 

 Here are the bugs and the adult beetles, alertly poised, 



