AQUATIC INSECTS 



Season: Emerging through late spring and midsummer. 



Distribution: Widely distributed throughout North America. 



Ephemera. — The rostrum of the nymph, the shelflike piece 

 on the front of its head, is divided by a deep round notch 

 into two spines (Fig. 154). The Ephemeras are smaller than 

 the Hexagenias but very similar to them in appearance and 

 habits (PI. XIII). 



Habitat. — They frequent smaller ponds, pools, and slow 

 streams where Hexagenias are not apt to be found. Outside 

 the large lake regions they are the commoner of the two 

 genera and even in some large lakes this is the case. 



Season. — Nymphs are emerging throughout the summer 

 season but the maximum swarming of the adults occurs in the 

 July twilights. Nymphs can be found at any time of the 

 year; during a recent mild winter in New England they were 

 collected each month from October to April. They were 

 found in considerable numbers beneath muddy banks along 

 with hibernating Hemiptera and spotted newts. 



^=*^ 



Pig. 156. — Nymph of Potomanthus, a mayfly 

 which sprawls on the mud. 



Potomanthus. — Nymphs of Potomanthus sprawl on the mud 

 but they are not burro wers (Fig. 156). Their tusks (mandibles) 

 are short, not extending beyond the head as they do in the 

 burrowers, Ephemera and Hexagenia (PI. XIII). They live 

 in the side waters of streams, not far from the swift- water 

 haunts of Chirotenetes. Length, nymph, three quarters of an 

 inch. The conspicuous adults have broad, pure white wings, 

 and at first glance appear more like moths than mayflies. 



Occurrence. — Adults, July-August. Northern New York, 

 Connecticut, Alassachusetts. 



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