V L 1 E S F K J r N E. 



No. 31. DARK MACKEREL. 



This is the name given to the insect represented 

 by the figure on the right hand side of the plate, 

 after it has changed from a dark kind of Green 

 Drake shewn on the left side. Both the male and 

 female change to the dark brown, but the former 

 is the smallest and darkest fly. Their habits are 

 similar in every respect to the Green and the Grey 

 Drake, (Nos. 28 and 29). Sir H. Davy says, that 

 " the Green Ephemera, or May Fly, lays her eggs 

 sitting on the water." (Salmonia, p. 249.) My 

 observations lead to the conviction that neither the 

 dark nor light Green Ephemera lay eggs, (being 

 imperfect insects,) but that their metamorphoses, 

 the Grey Drake and the Dark Mackerel, lay eggs 

 (whilst rising and falling, &c.)* This fly continues 



* The egg of this fly and that of all the last metamorphoses of the 

 Ephemeridae, here spoken of, sinks to the bottom of the water, and is 

 there, in a few days, hatched into a white grig; this larva undergoes 

 several transmutations before it becomes a nympha, which, rising to the 

 surface at its appointed season, bursts the case or skin which incloses 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, (see fig. 22, plate 11.) It then undergoes its last 

 metamorphosis, and enters upon its imago or perfect state, (see fig. 23), 

 changing the whole of its envelopes, even those of its line tails and legs. 

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



