CHAPTER XV 



AQUATIC INSECTS 



Insecta 



Water insects and water plants have several points in com- 

 mon. Both groups are very limited when compared with the 

 number of their terrestrial relatives and neither of them to any 

 extent inhabits deep water nor lives far from shore. In most 

 aquatic seed plants pollination occurs above the water; most 

 aquatic insects mate in the air or upon the surface of the water. 

 Aquatic insects live in the water mainly during their immature 

 stages and even these show many marks of terrestrial origin. 

 In aquatic insects, virtually all the adults breathe air and 

 many of them fly away from the water, returning only to lay 

 their eggs. 



The insects commonly known as aquatic are the stoneflies 

 or Plecoptera; the mayflies or Ephemerida; the dragonflies and 

 damselflies or Odonata; the water-bugs or Hemiptera; the net- 

 winged insects or Neuroptera; the caddis flies^ or Trichoptera; 

 the moths or Lepidoptera; the beetles or Coleoptera; and the 

 flies or Diptera. In addition to these there are the spring- 

 tails, Collembola, which gatherabout the pond-margins, spring- 

 ing up from the surface film, and a few species of very small 

 wasplike forms belonging to the order Hymenoptera, not in- 

 cluded in this book. All of these aquatic forms have the 

 typical insect structure and during their growth and life 

 history they go through the same changes of form as their 

 nearest land relatives. 



179 



