MAY FLIES AND MIDGES OF NEW YORK 23 



c Between the first and second anal veins is a bunch of 3-4 long, 

 straight intercalaries, conjoined basally before their attachment 

 to the principal veins ; the second anal vein nearly straight and 



unbranched Polymitarcys 



cc Between the first and second anal veins are only shorter, sinuate, 



and sometimes forking intercalaries, attached directly to the 



first anal ; the second anal vein sinuate and often branched 



(fig.S) 



d The median vein forked % to % its length ; vein CUo not more 



strongly bent at base than the first anal Euthyplocia 



dd The fork of the median vein occupying not more than half its 



length ; vein Cuo more strongly bent at base than is the first 



anal (fig.3) 



e The third anal vein simple, but attached to the hind margin by 



a number of crossveins ; in the narrow first fork of the 



median vein there are one or more crossveins before the 



origin of the vein Mo ; male forceps four-jointed 



f Caudal setae 3, (^ and $ ; fore tarsus of female imago % as 



long as the tibia Ephemera 



ff Oaudal setae 2 in c? and 3 in 9 ; fore tarsus of $ % as long 



as the tibia Pentagenia 



fff Caudal setae 2, (^ and 5 ; fore tarsus of $ as long as the 



tibia Hexagenia 



ee The third anal vein with a simple terminal fork and unattached 

 to the hind margin, although a few isolated short intercala- 

 ries lie between ; in the wider first fork of the median vein 

 there is no crossvein before the origin of vein Mo ; male for- 

 ceps 3-joiuted Potamanthus 



aa The cubital and first anal veins parallel at base (in a few forms with 

 reduced and scanty venation, appearing a little divergent) 

 1) Eyes of the male simple and remote; hind tarsi with 5 freely movable 

 segments ; venation never greatly reduced ; intercalary veins be- 

 tween the first and second anal veins unattached basally and in 

 two pairs, of which the pair nearer the hind angle is the longer 



(pl.4, figs. 3 and 4) , Heptageninae 



c Basal segment of the male fore tarsus not surpassed in length by any 

 of the succeeding segments 

 d Second segment about as long as the first and longer than the 



third E p e o r u s 



dd Second segment shorter than the first and about equal to the 



third Iron 



cc Basal segment of the male fore tarsus shorter than some of the 

 succeeding segments 

 d Basal segment of the male fore tarsus longer than the fifth seg- 

 ment, the second and third segments of unequal length 



e The second segment longer than the third E c d y u r u s 



ee The second segment shorter than the third C y n i g m a 



dd The basal segment of the male fore tarsus shorter than the fifth 

 segment, and the second and third segments of about equal 

 length 



