CHAPTEE XXI 



INSECTA (continued) 



Order V. : Neukoptera (continued) 

 Family 2 : Ephemeridae (the May-flies) 



The May-flies, like the Dragon-flies, have aquatic larvae, 

 and there is a gradual metamorphosis, the wings growing 

 rapidly at the last moult. The second pair of wings is always 

 much smaller than the first pair. The head bears short 

 antennae, and three ocelli, as well as a pair of large, some- 

 times subdivided, compound eyes. The mouth-parts are very 

 degenerate, for the imago does not feed during its short life. 



Type : The Common May-fly (Ephemera vulgata). 



The history of these insects is one that holds the imagina- 

 tion. For two or three years, the dingy little brown larvae 

 may live partially buried in the 

 mud or decaying vegetation at the 

 bottom of pond or river, swimming 

 actively, if disturbed, by whisking 

 their tails, but taking refuge as 

 soon as possible in the mud or 

 amongst the vegetation, remaining 

 very still with tail uplifted, as 

 shown in Fig. 230. Then, one 

 evening in summer, hundreds of 

 them rise together to the surface, 

 split their larval skins, and, in a 

 few brief moments, up dart the 

 winged flies, soon, however, to come to rest again in order to 



308 



Fig. 230. — Larva of the Com- 

 mon May-fly, resting on 

 a piece of Canadian Water- 

 weed. 



