viii MAY-FLIES 321 



in the evening they all disappear, and rest upon 

 plants throughout the night and the following day. 

 The duration of the winged state was not determined 

 with certainty, but it is short. The flies continue to 

 emerge for fifteen days or more in succession. 



" I have often seen the union of the male and 

 female. Hio;h in the air I have seen a male out of 



o 



a swarm of Ephemerae seize a female, and remain 

 attached to her ; they flew away to the top of a wall 

 where they settled together. The wall was too high 

 for me to see distinctly, but I could make out that 

 one of the pair, no doubt the male, curved the 

 abdomen round as if to seek the female. Swammer- 

 dam was no doubt much in error in supposing that 

 the eggs of Ephemerae are fertilised in the water. 



"After publishing these imperfect observations, I 

 was several years later amusing myself by the con- 

 templation of the aerial dances of swarms of Ephe- 

 merae, composed of males only, as they usually arc, 

 when I perceived that if a female mixed in the swarm, 

 as often happened, two or three males pursued her, 

 until one of them succeeded in flying away with her. 

 The pair ordinarily sought the top of a wall or the 

 summit of a tree, but two or three couples placed 

 themselves conveniently for observation on the leaves 

 of a neighbouring bush. I could see that the male 

 placed himself beneath the female, and curved his 

 abdomen upwards to gain the orifice of the oviduct. 

 The affair was ended in a moment, and the male flew 

 away. I should have been glad to observe the use of 

 the long fore legs and of the claspers of the male, but 

 my attention was fixed upon the movements of the 



Y 



