SYNOPSIS OF THE BRITISH EPHEMERID.E. 5 



side, exjDlains the use or rather the necessity of the double 

 penis, since each side requires to be separately fertilized. 



The other genera appear to live longer ; especially those 

 females which meet with no opportunity of copulation can 

 live a long while, and Stephens notices a female of C. dip- 

 terum which continued ahve for three weeks. The imago 

 takes no food, indeed its undeveloped maxillary organs are 

 quite unserviceable ; its sole object is the propagation of the 

 species, hence speedy copulation. For the accomplishment 

 of this the males perform in great numbers the well-known 

 dancing flight ; only very rarely is there a female in such a 

 swarm, for directly she appears she receives proposals from 

 one of the numerous males, and disappears with her consort 

 immediately from the swarm. Generally the female is found 

 sitting sideways in the grass, and probably requires a longer 

 time to prepare her for her more important mission. The 

 species of the genus Palingenia^ which, by their appearance 

 in such numbers, hke falling snowflakes, have long attracted 

 the attention of observers, are wanting in England. But 

 even the English species of Ccenls sometimes appear in 

 Prussia in such quantities, that objects near the water, such 

 as tables or windows of houses, are covered an inch thick, 

 and on the Cuiische-Nehrung they are used to feed the pigs. 



The best time for capturing EphemeridcE is evening and 

 night, especially on sultry, thundery days, but yet some 

 species of Potamanthus and Ej^hemera are also to be found 

 swarming in the air in great numbers in the morning and at 

 mid-day, but then they are almost all males. The free- 

 swimming larvje and pupse are easily netted in the water, 

 and these are not difficult to rear in ordinary aquariums in 

 which water plants are growing. The burrowing larvas (at 

 least Eph. vulgata) are easily found when one presses the 

 net along the side of the steep clay banks of ditches. I 



