AQUATIC INSECTS 



Their flattened bodies with thin, downcurved edges, their 

 knife-blade legs, and grappling claws are all adjustments to 

 life amid the constant pressure of moving water. Their 

 gills are platelike and together form a suction disk which 

 makes an efficient holdfast. 



In Iron the first and last pairs of gills are incurved so that 

 their tips come closely together; in Epeorus there is a space 

 between every pair and the oval which they make is not 

 complete. In Epeorus the body is wider, more flaring than 

 in Iron, 



Occurrence. — Adults emerge through May and July. Both 

 genera are widely distributed. 



Dragonfiies and Damselflies — Odonata 



Form and habits of adults. — The adults of this order are 

 the swift- winged dragonflies or devil's darning needles which 

 fly about the midsummer ponds on regular beats, round and 

 round, stopping on the same reeds like watchmen at their 

 time clocks. They are in pursuit of midges and such small 

 insect game which they capture on the wing. The damsel- 

 flies are leisurely, as they flit and loiter along the stream banks 

 while the dragonflies cut through the air like arrows. Both 

 groups of the Odonata have four wings with finely netted 

 veins ; when resting, dragonflies hold their wings straight out 

 horizontall}' from the body (Fig. 162); most damselflies fold 

 theirs close together vertically over their backs (Fig. 166). 

 Both have strong biting mouth parts and long bodies, very 

 slender, and often brilliantly colored in damselflies, stouter 

 and usually more somber in dragonflies. In all of the damsel- 

 flies and some of the dragonflies the female has an ovipositor 

 with which the eggs are placed within the leaves and stems 

 of water plants. IMany dragonflies skim the surface, dipping 

 repeatedly to drop the eggs into the water. Damselflies 

 sometimes go below the surface of the water to find a good 

 place for their eggs just as the little mayfly Bcetis goes under 



213 



Ja 



