MAY-FLIES 35 



greatly reduced and quite functionless, no food being 

 taken. Thus the final stage of the May-fly's life- 

 history is little, more than an expedient to secure the 

 perpetuation of the species. The wings, which are 

 traversed by a complex network of veins, are not 

 folded when at rest, but are brought together and 

 held erect above the back. The fore-wings are much 

 larger than the hind-wings the latter, indeed, being 

 quite absent in some species. The antennae are short 

 and inconspicuous, but the fore-legs are often very 

 long, and are extended beyond the head in a manner 

 suggestive of " feelers." The hindmost segment of 

 the abdomen bears at least two, often three, long 

 thread-like cerci. The eyes of adult May-flies are 

 remarkably developed, especially in the males. The 

 compound eyes of this sex in certain species are 

 divided, so that each part becomes virtually a separate 

 organ one portion being supported upon a kind of 

 horn or pillar, while the other occupies a more usual 

 position at the side of the head. Male May-flies 

 appear to rely chiefly upon sight to secure mates 

 during their brief twilight dances. 



So far as the writer is aware, the complete life-story 

 of a May-fly, from egg to imago, has not yet been told. 

 It is known, however, that the eggs are dropped into 

 the water by the female, and that the early stages of 

 development extend over a considerable period, in 

 some species perhaps as much as three years. The 

 nymphs vary greatly in form according to their habits, 

 but are always very unlike their parents, being rela- 

 tively robust, with well developed mandibulate mouth- 

 parts. They are entirely aquatic, and for the most 

 part feed on water-weeds, though some also devour 

 creatures smaller and weaker than themselves. Breath- 



