MAY PLIES AND MIDGES OF NEW YORK 



49 



covers part of the 8tli segment ; in d i in i n ii 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. h 11 a r i s 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 (pi. 11, 

 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 Tricorythus and the South Ameri- 

 can genus Leptophyes, than with Caenis . 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; 



