VI 



EPHEMERIDA 



Mayflies 



This is a small group of aquatic insects, very unique in 

 form and habits. The nymphs live in the water — in all fresh 

 waters — and are everywhere available. Adults are on the 

 wing for a brief season,* and are seen in flight only on certain 

 hours of the day. They are, therefore, little noticed by most 

 persons. Certain large species that emerge from the water 

 all at one time and swarm for a few days by the lake or 

 riverside are well enough known; for they fly to lights in 

 city streets and cover the lamp posts and sidewalks. The 

 cast skins they leave behind on emergence from the water 

 float on the surface and drift in windrows upon the shores. 



Being weak flyers and easy to catch, there is no difficulty 

 about obtaining specimens in any number at swarming time. 

 They are best preserved in alcohol. 



The most remarkable thing about this group is perhaps 

 the brevity of the life of the aerial adult f as compared with 

 the long life of the aquatic nymph. The longest lived adult 

 mayflies live several days, but their nymphs live several 

 years. The shortest lived among them live as adults but a 

 few hours. Mouthparts are lost at transformation, and hence 

 there is no more feeding after that, but only swarming and 



* Whence the name of the order: ephemeros, living but a day. 

 t Read in this connection Benjamin Franklin's Soliloquy of a Venerable 

 Mayfly, that had lived 420 minutes. 



60 



