Kl'IIEMERID/E OF OTHER RlVERS. 17 



as is abundantly proved by the fact that the male spinners are 

 only to be distinguished from the Great Bed Spinners by their 

 slightly smaller size. The dun is inclined to be- rather like 

 the dun of the Yellow Upright, Rhithrogena semicolorata, 

 which is itself described as resembling a large pale Olive. 



The Yellow Upright the duns of this fly are like a large 

 Pale Olive, but the spinners are identical with those of 

 the Little Yellow May Dun. The name Yellow Upright is 

 derived from the general colouring of the male spinner combined 

 with his habit during flight of ascending vertically with body 

 rigidly erect. It must not be associated in any way with the 

 appearance of the Dun, which is not yellow, nor does it assume 

 an upright position when on the wing. Of course the spinners 

 of the Little Yellow May Dun are also called Yellow Uprights. 

 They have the same habits in flight. 



Beware of the genus Cloeon. It contains three species 

 which inhabit still or very quiet water. You are apt to wonder 

 whether they are Olives or Pale Wateries, but you can very 

 easily prove that they are neither by observing that the small 

 hind-icings are absent. This is the only genus w 7 ith two wings 

 and two setae. 



The genus Siphlurus is represented by two species. S.armatus 

 is about the same size as a May-fly. The dun has wings of a 

 light brownish grey colour. 



The spinners are much alike in both sexes. Wings : clear, 

 tinted with greenish grey. Neuration : light brown. Thorax : 

 pitch brown. Abdomen : reddish brown above, yellower on 

 the underside. 



S.lacustris. About the same size as S.armatus, sometimes 

 a little smaller. The dun wings are light brownish grey. 



The imago is much alike in both sexes.. Wings : clear with 

 brown neuration. Thorax : jet black between the wings. 

 Abdomen : dingy brown above and dark greenish grey below. 



Ameletus inopinatus labours under grave suspicion of being 

 an alien. The Eev. A. E. Eaton confesses that he has never 

 seen a home-bred specimen, but the fly is included in Dale's list 



