107 



16. — Notes on the May Fly. 



By Peter Hood, M.D. 



[Read 13th June, 1878.] 



Plate I. 



Perhaps the most interesting of all our aquatic insects — to the 

 fly-fisherman more especially — is the green drake or May fly — 

 Ephemera vulgata — which belongs to the order Neuroptera, and the 

 family JEpJiemeridce. 



This fly proceeds from a water nympha and lives as the green 

 drake (the sub-imago state) for one or two days ; then the female 

 changes to the grey drake, and the male to the black drake. The 

 green drake cannot be said to be in season quite three weeks on an 

 average. Its season depends greatly on the state of the weather ; 

 and it will be found earlier on the slowly running pai'ts of a stream 

 (such as mill dams) than on the rapid places. The grey drake 

 lives three or four days after her metamorphosis from the female 

 green drake, and is caught by the fish whilst laying her eggs on 

 the water. The term of existence of the black drake is about the 

 same as that of the female. He is smaller than the female, and is 

 erroneously supposed by some, who call him the death drake, to 

 kill her. 



It has been asserted by those who have devoted attention to the 

 observation of the May fly, that exactly one year elapses, almost to 

 a day, from the time the eggs are laid by her to the appearance of 

 the flies on the water. That they do appear within a few days of 

 this period there is no doubt, but the evolution from the larva 

 state to that of the beautiful fly is much dependent upon the 

 weather, and more especially also on the temperature of the water. 

 I have not been able to ascei'tain at what period after the egg has 

 been deposited by the female (Avhich sinks like a shot to the bottom 

 of the water) it is hatched, to form the larva, or maggot-like 

 looking object, and I am afraid it may be long before such in- 

 formation reaches us. I extract the following from Ronald's 

 ' Fly-fisher's Entomology ' (p. 92), it being the most detailed 

 account I have been able to obtain: — "The egg of this fly ... . 

 sinks to the bottom of the water, and is there, in a few days, 

 hatched into a white grig ; this larva undergoes several transmuta- 

 tions before it becomes a nympha, which, rising to the surface at 

 its appointed season, bursts the case or skin which encloses it (at 

 the shoulders), displays beautiful wings, quits its old husk, and, 

 after the lapse of a second or two, generally flies to the nearest terra 

 firma, where it remains in solitude and shelter (from the wind and 

 sun-beams) for about two days. It then undergoes its last 

 metamorphosis, and enters upon its imago or perfect state, 

 changing the whole of its envelopes, even those of its fine tails and 

 legs. The tails and the two fore-legs of the male increase to about 

 double their former length, those of the female receive an accession 



