ADAPTATIONS OF AQUATIC INSECTS 185 
and larvee of mosquitoes and black-flies on microscopic organ- 
isms near the surface, while larvee of Chironomus 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 
/ 
Backswimmer, Notonecta insulata, Water-skater, Gerris remigis, natural size. 
natural size. 
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 
Fic. 2206. 
kill small fishes by their poisonous punc- 
tures. Some other kinds, as the water- 
skaters (Gerride, Fig. 225), depend on 
dead or disabled insects. The species of 
Hydrophilus (Fig. 226) are to some ex- 
tent carnivorous as larve but phytopha- 
gous as imagines, while Dytiscidz 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 
mom the attacks of parasitic species. A  2»drophlus sriangularss, 
natural size. 
few Hymenoptera actually enter the 
water to find their victims, for example, the ichneumon A grio- 
typus, which lays its eggs on the larvee of caddis flies. 
