THE HARLEQUIN-FLY iig 



suggested the natne Chironomus, which may be translated 

 Harlequin-fly. 



On summer evenings the male flies gather in great swarms, 

 often containing several thousands of individuals, in the 

 neighbourhood of the streams or pools in which the larval 

 stage is passed. Here they perform an aerial dance, rising 

 continually to the top of the swarm, and then slowly subsiding. 



Fig. 66.— Egg-masses of Chironomus. A, egg-rope of C. dorsalis, divided into 

 sections, to show both sides ; B, twisted fibres, which traverse the egg-rope ; C, egg- 

 mass of another species of Chironomus ; D, egg-mass of a third species ; E, part of egg- 

 mass, more highly magnified ; F, developing eggs, two stages. 



Females are rarely seen in the swarms, and the purpose of 

 these singular gyrations was long obscure. But it has been 

 recently observed by Mr T. H. Taylor that on windy evenings, 

 when the swarm is blown hither and thither, a certain propor- 

 tion of females may be found among the males. A female fly, 

 immediately after emerging from the water, joins the nearest 

 swarm, and in still weather is mated at once. Then she flies 



