ADAPTATIONS OF AQUATIC IN.SECTS 



i8 5 



and larvae of mosquitoes and black-flies on microscopic organ- 

 isms near the surface, while larvae of Ckironomits find food in 

 the sediment that accumulates at the bottom of a body of 

 water. 



Predaceous species abound in the water. Notonecta (Fig. 

 224) approaches its prey from beneath, clasps it with the front 



FIG. 224. 



FIG. 225. 



Backswimmer, Notonecta insulata, 

 natural size. 



Water-skater, Gerris remigis, natural size. 



FIG. 226. 



pair of legs and pierces it. Nepa and Ranatra likewise have 

 prehensile front legs along with powerful piercing organs. 

 Belostoma and Benacus (Fig. 22) even 

 kill small fishes by their poisonous punc- 

 tures. Some other kinds, as the water- 

 skaters (Gerridse, Fig. 225), depend on 

 dead or disabled insects. The species of 

 Hydrophilus (Fig. 226) are to some ex- 

 tent carnivorous as larvae but phytopha- 

 gous as imagines, while Dytiscidae are car- 

 nivorous throughout life. Aquatic insects 

 eat not only other insects, but also worms, 

 crustaceans, mollusks or any other avail- 

 able animal matter. 



Even aquatic insects are not exempt 

 from the attacks of parasitic species. A 

 few Hymenoptera actually enter the 

 water to find their victims, for example, the ichneumon Agrio- 

 typus, which lays its eggs on the larvae of caddis flies. 



Hydrophilus triangularis, 

 natural size. 



