24 NEW YORK STATE MUSEUM 



e Basal segment of the male hind tarsus longer than the third 



segment Rhithrogena 



ee Basal segment of the male hind tarsus shorter than the third 



segment Heptagenia 



6& Hind tarsi usually with but four freely movable segments, the basal 

 segment being more or less completely consolidated with the 

 tibia ; eyes of the male enlarged, often approximated on the dorsal 

 side and divided into superior and lateral portions with corneal 

 facets of different size; venation various, sometimes greatly re- 

 duced ; intercalary veins between the first and second anal never 



as in ft above Baetinae 



c The three anal veins nearly parallel to the hind margin of the wing 

 and to each other, ending in the outer margin ; in the hind wing 

 the branches of the radial A'ein are strongly unilateral on the an- 

 terior side Baetisca 



cc Anal veins strongly divergent distally, usually both the second and 

 the third ending in the hind margin ; forks of the radial vein in 

 the hind wing more symmetrical 

 d The median vein with a normal fork ; hind wings, when present, 

 usually but little longer than broad and with a copious 

 venation 

 f The intercalaries between the first and second anal veins 

 variable, but usually more or less independent, and not 

 directly dependent from the first anal ; three well-devel- 

 oped caudal setae (except in Bias turns, in our 

 fauna) 

 g Hind wings present 



h Vein ^L and bisector of the cubital fork independent; 

 between the latter and vein CU; no intercalaries ; vein 

 CUj in the hind wing rarely preserved ; caudal setae 

 generally much longer than the body ; penultimate 

 segment of the male forceps shorter than the ante- 

 penultimate 

 / In the hind wing the subcostal vein reaches nearly to 

 tlio wing apex ; male forceps threo-.iointed 

 / Hind wing with a slight concavity at the niitMlo ot 

 costal margin ; 5-0 longitudinal veins between 

 Rj and Ro; veinlets numerous about the wing 

 margins and crossvoins nuniorous in tlie hind 

 wings 

 Tc Third anal vein of the hind wing wanting; caudal 

 setae of about equal length . . . . L e p t o p h 1 e b i a 

 klc Third anal vein of the hind wing present, and often 

 followed by one or twD additional intercalaries; 

 median caudal seta distinctly shorter than the 



others B 1 a s t u r u s 



// Hind wing with an angular Inlie projecting forward 

 from the middle of (he costal margin ; 4 longitud- 

 inal veins between R. and R^; wing margins free 

 from veinlets, and few crossveins in hind wing 



IT a b r p h 1 e b 1 a 



