MAY FLIES AND MIDGES OF NEW YORK 25 



ii In the hind wing the subcostal vein terminates in the 

 costa at hardly more than half the length of the 

 wing, just beyond the obtuse angulation having a 

 thickened margin ; forceps of male more or less dis- 

 tinctly four-jointed Choroterpes 



hit Vein M 2 and the bisector of the cubital fork both tending 

 to attach themselves to the posterior branch of their 

 respective forks; between the latter and vein Cu a 

 are generally some short intercalaries (the cubital 

 region thus being better developed than in group h) ; 

 caudal setae about as long as the body; penulti- 

 mate segment of the male forceps longer than the 

 antepenultimate 



i Veins Cu 2 and 1st A separate to base. .Ephmerella 

 ii Veins Cu 2 and 1st A fused toward the base 



D r u n e 1 1 a gen. nov. 



gg Hind wings absent Caenis 



if The intercalaries between the first and second anal veins repre- 

 sented by a series of veinlets, often sinuous or forking, 

 extending directly from the first anal to the wing margin ; 

 costal angulation of hind wing close to the base ; but two 

 well-developed caudal setae, the median one being rudi- 

 mentary or wanting ; basal joint of hind tarsi evident but 

 not well developed 



g Median caudal seta a distinctly segmented rudiment (pl.6, 

 fig.l); forceps of male three-jointed; posterior pro- 

 longation of sternum of ninth segment of abdomen of 

 female bifid at tip 



h Basal segment of fore tarsus of male shortest ; claws of 

 each tarsus unlike each to each ; hind wing with the- 

 costal angulation acute, and the fork of the median 

 vein occupying two thirds the length of that vein 



Coloburus 



hh Basal segment of fore tarsus of the male longest ; claws 

 of each tarsus alike ; hind wing with the costal angula- 

 tion obtuse, and the median vein forked through one 



third its length Chirotenetes 



gg Median caudal seta more rudimentary or wanting; forceps 

 of the male distinctly four-jointed; posterior prolonga- 

 tion of the sternum of the ninth abdominal segment in 

 the female entire at tip 

 h Claws of each tarsus alike ; caudal setae at least one 



half longer than the body Siphlurus 



Tih Claws of each tarsus unlike; caudal setae about as 



long as the body in both sexes Ameletus 



dd Median vein apparently simple, its posterior fork (M 3 ) being 

 detached and appearing as an intercalary ; hind wings when 

 present at least twice as long as wide, and provided with 

 but 1-3 longitudinal veins 



