ilFilEMKIUD.E. EPilE.MKllA. 55 



and which is rolled vxp into a mass on each side of the thorax : in 

 the first three states these insects inhabit the water, and upon their 

 emersion from the pupa they become inhabitants of the air ; their 

 life is of short duration, but nevertheless some of the species exist 

 for a considerable period, as noticed under Cloeon dipterum : the 

 larvaj vary slightly in structure, according to the genera, those of the 

 true Ephemerae and of Baetis having exserted respiratory organs 

 along both sides of the body. 



The indigenous genera may be thus distinguished : — 



Alie quatuor, posticis distinctis : 



C'«?///a triseta : . . . . .3. Ephemera. 



biseta : . . . . .5. Baetis. 



duse, posticis nullis, aut vix coiispicuis : 



Cauda triseta : . . . . .4. C^enis. 



biseta: . . . . . (J. CLoiioN. 



Genus III.— EPHEMERA Auctorum. 



Head small, emarginate in front ; eyes rather large, ovate, united on the 

 crown in the males, somewhat remote in the females ; thorax not very stout, 

 elongate-ovate ; wings four, anterior much longer than the abdomen, some- 

 what lanceolate, more or less reticulated, the costa slightly waved, posterior 

 very small, ovate-triangidar ; abdcmitn as long again as the thorax, slightly 

 tapering at the apex, and terminated by three very long filaments, of which 

 the central one is shortest in the males ; Itgs rather long and slender. 



The species of this genus ai*e probably more numerous than I 

 have indicated, as the account of them is entirely made up from 

 tliose that are contained in my own cabinets, other collections 

 thereof not being named or divided into species : it is therefore fair 

 to conclude, that if among the more conspicuous long genera I 

 occasionally lack specimens, such is the case in this genus, which 

 may be known by having four wings and three filaments, or setae, at 

 the apex of the abdomen. 



A. The transverse uervures of the wings very distinct, giving the wings a 

 strongly reticulated appearance. 



Sp. 1. vulgata. Obscui'e-fusca, abdomine lutescente, alls fuscescentlbus, ftisco 

 rrticuhitis ci macidatis, costa anticar'um palUdefusca, pedibus pallidis obscure 

 7iebidosis. (Exp. Alar. 1 unc. 2-4 lin.: — Long. corp. 6 — 7^ lin.; 1. setarum 

 1 unc. 3 — t lin.) 



V.[). vulgata. Linnc.— U'uod, v. ii, pL 47. — Slcjfh. Calal. 30j. xVo. 336D. 



