58 KEUROPTERA. 



genera Baetis, Chloe\ and Coenis, are exquisitely 

 beautiful and delicate in form. 



The genus Ephemera is characterized by the posses 

 sion of three nearly equal hair-like appendages at the 

 end of the tail ; they are longer in the male insect, 

 which is further distinguished by two curved clasping 

 organs at the end of the abdomen. The May-fly 

 deposits her eggs by little packets at a time, first in one 

 place, now in another, in the water ; they soon sink 

 and become attached to submerged weeds and stones ; 

 soon they change into larv?e, very curious creatures 

 indeed ; in their larval stage they are believed to live 

 for two or three years, during the whole period of which 

 they are active eaters. I have found the intestinal 

 canal of the Lvva to contain the spores of numerous 

 algae, small crasfcacea, rotifera, etc. Both larvae and 

 nymphse are often found in holes in river banks, and 

 frequently in the sand or mud at the bottom of the 

 water. The only difference between larva and nympha 

 is that the latter has sheaths for the wdngs, which are 

 rolled or crumpled up inside. The banks of rivers may 

 often be seen to be riddled by these larvae, which tunnel 

 for themselves tubular galleries in the mud to the depth 

 of four and five inches. The larvae of some other 

 members of the May-fly family, instead of living in 

 sand or in tubular galleries, swim from place to place, 

 resting on the leaves and stems of water plants. The 

 abdomen of the larva and nympha of Ephemera vulgata 

 is bordered on either side by a row of gills, which, by 

 their constant motion, serve to draw fresh currents of 

 water to oxygenate the blood. Eacli gill consists of two 

 large trachial trunks, in which small air vessels ramify in 



