INSECTA. 423 



Sub-genera : Lestes, Galepteryx, Agrion LEACH, Mecistogaster 

 RAMBUR, and some others of this author, 1. 1. p. 217. 



Family XXXII. Ephemerince. Parts of mouth soft. Antennas 

 very short, subulate, triarticulate. Tarsi quinquearticulate, with 

 i first joint mostly very short, scarcely distinguishable. Posterior 

 wings less than anterior, sometimes none. Abdomen terminated by 

 two or three filaments. 



Ephemera L. (Characters of the family.) 



May-Flies, bank-bait. The larvae and nymphs live at the bottom 

 of the water between stones, or in the ooze ; some dig horizontal 

 passages, in which they move very rapidly. In these two states 

 they live two or three years before changing into perfect insects j 

 they proceed from very small eggs. The larva has always three 

 threads at the abdomen, of which the middle one in many species 

 disappears after the metamorphosis \ it is distinguished especially 

 from the perfect insect by longer antennae, by stronger upper jaws, 

 and by external respiratory organs at the first six rings of the abdo- 

 men ; the air-tubes appear as free threads or little plumes, or are 

 united by membrane to form a foliated lamina. Some larvae have 

 on each side of every ring two such plates. The change from 

 nymph to perfect insect occurs in JEphemera Swammerdamii (Palin- 

 genia longicauda BURM.) so suddenly that there is almost at the 

 same moment a creeping and a flying creature. In other species, as 

 in those observed by RCESEL, the change takes place more slowly. 

 They moult once again in their perfect condition ; and if we be 

 walking by the banks of the water over which they are flying we 

 often see this moulting performed on our clothes. 



In the middle of summer the May-Fly takes wing towards even- 

 ing. The time of flight differs in different species. That which 

 SWAMMERDAM described shews itself nearly three days in succession, 

 about St John's day, in the month of May, and often in such quan- 

 tities that it is as difficult to count these little creatures as falling 

 snow-flakes. A great many^fall into the water a prey to fishes, and 

 at that time, especially at Dordrecht, the roach is noted as being 

 peculiarly fat and good. Hence the name bank-bait, oeveraas (in 

 some parts of France la manne). According to the relation of 

 SCOPOLI they are collected by the country-people in Carniola to 

 manure the land (Entomol. Carniol. p. 264). 



