MAY FLIES AND MIDGES OF NEW YORK 



49 



covers part of the 8tli segment ; in d i m i n n t a it does not wholly 

 cover the 7th segment. 



Were it not that these differences of structure of the nymph 

 are so slight I should have thought a separate genus necesisary 

 for this new species; for the differences in venation and in the 

 genitalia are certainly as great as usually serve for generic 

 separation. These principal differences may be tabulated as 

 follows: 



Character 



Caenis diminuta, 

 hilar is, etc. 



C. allecta 



Anal veins 



disconnected 



absent 



conjoined basally 



present 



pluriserial 



three-jointed 



bilobed at sides and emarginate 



Vein M2 



Crossveins 



uniserial 



Forceps of male .... 

 Basis 



one-jointed 



straight edged 





in the middle 



Among some mayflies that were kindly collected for me b^ 

 Mrs Mary Kogers Miller at Thousand Island Park, on the St 

 Lawrence river, are a number of typical specimens of our two 

 previously described species, 0. diminuta Walker and 

 0. h i 1 a r i s Say, that fit the descriptions exactly. In ordet 

 to promote accuracy in the deitermination of the most difficult 

 forms, I have prepared the drawings herewith presented (pl.ll, 

 figs.3-6) of the wings and male genitalia of these species. It 

 will be observed by comparing the wings with Eaton's figures 

 that in venational characters ? C. allecta agrees better with 

 the Europaean genus Trsicorythuis and the South Ameri- 

 can genus L e p t o p h y e s , than with O a e n i s . But there 

 are disiagreements also with these, and the J^ genitalia and 

 nymphs of these are as yet not certainly known. 



Leptophlebia praepedita Etn. ? 



This species, hitherto known only from ^N'ew Hampshire and 

 not yet reported from New York State, is common about Lake 

 Forest, Illinois, where 1 have found it in three quite diverse 

 situations: 1) in the Skokie (north branch of Chicago river), a 

 sluggish creek flowing through open meadows and marshes; 



