14 SYNOPSIS OF THE EPHEMERIDJE 



Hinder tarsi five-jointed. Eyes of the male 



evenly contoured and undivided; their 

 lower and lesser facets sometimes different 

 in colour from the upper and larger facets. 

 Fly usually large . . . . .10 



8. Hind wings minute ..... 9 



Hind wings completely absent . . CLOEON. 



9.- -Hind wings broad, obtuse . . . BAETIS. 



Hing wings minute, very narrow. 



CENTROPTILUM. 



to. Tarsus in the hinder legs shorter than the 

 tibia, even when subequal in length 

 thereto ; its first joint hardly perceptibly 

 shorter than the second ; the claws 

 mutually dissimilar, one blunt, the other 

 hooked ..... AMELETUS. 



Hind tarsus longer than the tibia ; its first 



joint distinctly longer than the second ; 

 tarsal claws all narrow and hooked. SIPHLURUS. 



Hinder tarsi shorter than the tibiae . .11 



1 1 . Lobes of the male intromittent organ narrow. 



Femora usually marked in the middle 

 with a dark spot or elongate streak. 



RHITHROGENA. 



Penis lobes broad. Femora in some cases 



dark-banded in the middle, not spotted . 12 

 12. First joint of the hind tarsus shorter than the 

 second joint. Flies yellowish in their 

 general colouring ; the wings of the 

 sub-imago especially so . . HEPTAGENIA. 



First joint of the hind tarsus as long as 



or longer than the second joint. Flies 

 brownish, varied with black ; wings of the 

 sub-imago greyish, and in some species 

 (e.g. venosus) are crossed by dark bands 

 before the moult .... ECDYURUS. 



Let us suppose that the angler has caught his 

 fly, and being anxious to identify it, refers to 

 the above table. The fly, we will assume, is a 



