AQUATIC INSECTS 



It is a rich chocolate brown color with a light median stripe 

 extending from the mouth and running over the head onto 

 the thorax ; the front tarsi are white. Chirotenetes is a mayfly 

 that has the habit, rare among mayflies, of taking a mixed 

 djet of alg« and midge larvae. Fullgrown nymphs are an 

 inch long. 



Occurrence. — May-July. Generally distributed through 

 North America. 



Family Heptageninae, Heptagenia. — The HeptagenincE are 

 flattened nymphs which live in rapid streams or on wave- 

 beaten shores (PI. XV). 



In most regions the Heptagenias are the commonest mayflies 

 of running water and they are by far the most generally 

 distributed of the flattened, clinging nymphs. Their hardi- 

 ness and their ability to endure changes in temperature and 

 differences in current is probably responsible for their pres- 

 ence in so many varieties of streams. They avoid the light, 

 staying on the under surfaces of the stones, and a brook 

 which looks utterly deserted may shelter hundreds of them. 

 They can be found all the year; in January the caddis worms, 

 Hydropsyche, are with them by hundreds. 



When fullgrown they migrate into quiet waters to emerge. 

 Dr. W. A. Clemens calculated that Heptagenias take a year 

 to complete their life cycle, spending all but four or five days 

 of this time in the water. About two months after their 

 mating and egg-laying season he began to find the small 

 nymphs. 



Occurrence. — Adults emerge through June and July. 



Epeorus, Iron. — These nymphs have flattened bodies but 

 only two tail filaments (PI. XV). Nymphs of both these 

 genera live in the most rapid currents, swift eddies, torrents 

 and water-falls. The members of both groups are very 

 beautiful insects, exceedingly delicate, susceptible to changes 

 in temperature, and able to live only a very short time in still 

 water. 



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