MAY PLIES AND MIDGES OP NEW YORK 



49 



covers part of the 8th segment ; in d i m i n u 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 necessary 

 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 : 



Among some mayflies that were kindly collected for me bj 

 Mrs Mary Rogers Miller at Thousand Isdand Park, on the St 

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

 previously described species, C. diminuta Walker and 

 C. hilaris Say, that fit the descriptions exactly. In ordet 

 to promote accuracy in the determination 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 Tracorythus and the South Ameri- 

 can genus Leptophyes, than with O a e n i s . But there 

 are disagreements also with these, and the <$ genitalia and 

 nymphs of these are as yet not certainly known. 



Leptophlebia praepedita Etn. ? 



This species, hitherto known only from New Hampshire and 

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

 Forest, Illinois, where I 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; 



