NATHAN BANKS. 247 



6. Vein 6 simple, some apical short intercalary veins, margin not ciliated, eyes 



of % turbinate Bsetini. 



Vein 6 forked, no apical short intercalary veins, margin ciliated, eyes of male 

 not turbinate, widely separate, but two wings Csenini. 



The Baetiscini includes only one genus, Bcetisca. The genus is 

 remarkable on several accounts, which justify the tribe for it. It 

 is, I think, most nearly allied to Heptagenia. 



The Leptophebini includes two genera in our fauna, which are 

 separated as follows : 



Hind wings more or less angulate on costa near base; costal cross-veins usually 

 not very irregular at outer costal curve ; two setae ; eyes of % separate ; 

 hind tarsi 5-jointed Heptagenia. 



Hind wings not angulate on costa near base; costal cross-veins at outer costal 

 curve more numerous, curved and irregular; seta? three; eyes of % 

 contiguous, hind tarsi 4-jointed Leptophlebia . 



The Siphlurini also embraces two genera in our fauna ; possibly 

 Siphlurus can be divided on good characters, but I do not think 

 those previously used are of generic value. 

 Basal costal cross-veins none or extremely indistinct; three setae. 



Ephemerella. 

 Basal costal cross-veins distinct, at least some of them ; but two setae. 



Siphlurus. 



■ The Ephemerini are represented by three genera, which can be 

 separated as follows : 



1. A series of basal cross-veins from 9 ' to anal margin, vein 9 rarely connected 



to branches of 8 2. 



No series of basal cross-veins from 9 ' to margin, at most two or three, vein 9 

 usually connected to branches of 8; three setae, but the median one in 

 % is very rudimentary Peutagen ia. 



2. Three suhequal seta? ; wings often maculate Ephemera . 



But two setae, the median very rudimentary, wings not maculate. 



Hexagenia. 



The Polymitarcini includes only the genus Polymitarcys in our 

 country. The European Jolia probably belongs to the tribe. 



The Csenini includes in our country only Comix, other genera are 

 known in Asia. 



The Bsetini embraces four genera, separable as follows : 



1 With but two wings ( la im 



With four wings 2. 



2. No basal costal cross-veins 3. 



Basal costal cross-veins distinct < a 1 1 i l»a- 1 i s. 



3. Short apical intercalary veins in pairs Ba?l i*. 



Short apical intercalary veins single O'eiif ropt iliiin. 



TRANS. AM. KNT. SOC. XXVI. MAY, 1900. 



