MAY-FLY. 415 



short-lived insects. The most familiar species is the ephemera 

 vulgata, or common May-fly, so plentiful in the early part of 

 summer, about the brinks of rivulets and stagnant waters. It is 

 of a greenish brown colour, with transparent wings, elegantly 

 mottled with brown, and is furnished at the extremity of the body 

 with three very long black bristles. It flutters during the evening 

 about the surface of the water, but during the day is generally- 

 seen in a quiescent posture, with the wings closed, and applied to 

 each other in an upright position. The larva is of a lengthened 

 shape, about an inch in length, furnished along each side of the 

 body with several finny plumes, and at the tail with three long 

 feathered processes : it has also a pair of moderately long antennae, 

 though those of the complete insect are extremely short. When 

 arrived at its full size, as above-described, it exhibits the rudi- 

 ments of wings on the back, in the form of a pair of obiong 

 sheaths or scales : its colour is a pale yellowish or whitish brown. 

 It is supposed to continue two years in this state of larve before it 

 changes into the complete insect. This change takes place in the 

 evening, when the larva rises to the surface of the water, and 

 soon divesting itself of its skin, flies to some neighbouring object; 

 and after having remained some time longer, again casts its pelli- 

 cle, and appears in its ultimate or perfect form, in which, as well 

 as in its larva state, it is a favourite food of several kinds of fishes, 

 and particularly of the trout. In some seasons it is extremely 

 plentiful, the air in the immediate neighbourhood of its natal 

 waters being frequently blackened by its numbers during the even- 

 ing hours. We are assured by Scopoli, that such swarms are pro- 

 duced every season, in the neighbourhood of some particular spots 

 in the neighbourhood of Carniola, that the countrymen think they 

 obtain but a small portion, unless every farmer can carry off about 

 twenty cart-loads of them into his fields, for the purpose of a 

 manure. 



But, of all the European ephemera?, that which has been most 

 celebrated, and of which almost every reader must recollect the 

 general and superficial account, so often detailed in works of 

 natural history, is the species described by Swammerdam *. It is 

 of a white colour, with the anterior rib of the upper wings black, 



* Ephemera horaria?? Linn, 



