VIII MAY-FLIES 315 



take wing. I found that when Ephemerae fell upon a 

 napkin spread over my knees, they could only rise 

 into the air with the help of their long tail-iilaments, 

 which gave a momentary support to the body. 



" The male fly of Polymitarcys has the middle 

 tail-filament much shorter than the two others, and 

 only from one-sixth to one-eighth of their length. 

 Two pairs of appendages project from the under side 

 of the extremity of the abdomen of the male, which 

 seem to correspond to the clasping organs of other 

 male Insects. 



" The eggs produced by the female fly are intended 

 to be laid in the water of the river, but as if in 

 ignorance she often deposits them on any object on 

 which she may happen to alight. The eggs are 

 grouped in two oval masses, from one-third to a 

 quarter of an inch in length. I counted 350 eggs in 

 one such mass. The short life of the winged female 

 compels her to deposit her 700 or 800 eggs at once, 

 without much discrimination of likely and unlikely 

 places. When the bucket containing a lantern and 

 covered with a cloth attracted Ephemera; from a 

 distance, many of these laid their eggs on the cloth. 

 The female turns up the extremity of the abdomen 

 nearly at a right angle, and the orifices of the two 

 oviducts, which open behind the sixth [the figure 

 seems to indicate the seventh] abdominal segment, 

 are exposed ; from these the tv 'o clusters of eggs are 

 passed out at the same time. When the eggs have 

 been discharged, two vesicles, apparently filled with 

 air, project from the orifices of the oviducts ; these 

 are probably either principal or subsidiary aids in the 



