FLAT-WINGED GROUP 



3135 



MALE OF COMMON MAY FLY, 



Ephemera vulgata. 

 (Natural size.) 



however, which do not live for even the proverbial day, but emerge one evening, 

 only to perish before the sun again appears. There is less truth in the supposition 

 that these insects appear only in May; May flies of one species or another being 

 seen on fine days throughout the summer and autumn. They are to be found in. 

 the neighborhood of rivers and lakes, some flying 

 only by night, and others during the cooler hours of 

 sunlight, or on favorable evenings until a little after 

 sunset. During the heat of the day they seek re- 

 pose, with their wings raised vertically. If the day 

 be cold and raw, they seldom fly, but remain under 

 shelter. In fine weather, however, they may some- 

 times be seen assembled together in swarms about 

 sundown, and engaged in their pastimes, which are 

 continued till some time after sunset. The peculiar 

 up-and-down movement, which marks the flight of 

 some species, has been often observed; and the mazy 

 dance of the May flies has been described by more 

 than one author. In these dancing assemblies the 

 male insects always greatly outnumber those of the 

 other sex. The larvae of the Ephemerida live in 

 water; a few kinds are carnivorous, but most feed 

 upon the minute vegetation scattered through the 

 mud or covering stones, and the larger aquatic plants. 



Many remain concealed in the banks or under stones, while others rove among 

 water weeds, and swim with celerity. The larvae of some genera are found only 



in large rivers. The eggs are, in some 



cases, 



deposited at the surface of the 

 water, and then sink to the bottom; but 

 in others the female creeps into the water 

 to lay her eggs in patches on the under 

 side of stones. The eggs are exceedingly 

 numerous, and vary in shape according- 

 to the genus. The larvae cast their skin 

 several times; they are at first without 

 special organs of respiration, but when 

 they are about eight or ten days old 

 tracheal gills begin to appear and ulti- 

 mately develop into forms, which vary 

 somewhat in the different genera. The 

 gills are attached in pairs to the sides of 

 some, or all, of the first seven segments of 

 the abdomen, in some species standing out 

 straight from the sides, and in others turned 

 over the back The mouth organs of the 

 larvae are better developed than in the 



A MAY FLY AT ITS FINAL MOLT, WITH THE 

 IMAGO ESCAPING FROM THE SKIN OF 

 THE SUBIMAGO. THE LARVA BELOW. 



