MAY PLIES AND MIDGES OP NEW YORK 29 



of pl.27 of Eaton's Monograph with those of iny pi. 5 and^6 will 

 show the close agreement of it with Oh. alboinanlcatus, 

 and demonstrate its generic position. The adult which Joly 

 furnished Eaton as having been bred from this species of nymph 

 was doubtless a poor specimen of Polymitarcys virgo 

 Oliv. This was suspected by Eaton and yet he allowed the adult 

 to determine the position of the species in his system. Doubt- 

 less the nymph J o 1 i a furnished a reason for including 

 Oligoneuria and its allies in the Ephemerinae also. 

 The nymph of Oligoneuria is certainly nearest C h i r o- 

 t e n e t e s of all forms hitherto described; and it has not yet 

 been shown that the very degenerate images may not as well 

 have descended from this part of the series, and belong in the 

 B a e t i n a e as here understood. My present ideas of the 

 major natural complexes of the order may be expressed as fol- 

 lows: 



1 Subfamily Ephemeriiiae;a fairly homogeneous series.^ 



2 Subfamily Heptageninae; a very homogeneous series. 



3 Subfamily Baetinae; a very heterogeneous series, only 

 definable as lacking the characteristics of the other two, and in- 

 cluding five fairly distinct groups, some of which may be found 

 worthy to rank as equivalents of 1 and 2 above : 



a) The group of Oligoneuria (Oligoneuria to Homeoneuria 

 of Eaton; pis. 3 and 26 of his monograph); five genera, represented 

 in tropical America and in the old world 



&) The group of B a e t i s , including all our genera of Baetinae 

 except B a e t i s c a , and many exotic genera 



c) The group of Baetisca, including B a e t i s c a only 



d) The group of Prosopistoma, including the exotic Prosopis- 



t m a only 



e) Tlie group of the nameless Chilean nymph figured on pi. 53 of Eaton's 



Monograph 



^ These three subfamilies, which I indicated parenthetically in my key to 

 nymphs published in bulletin 47, I had already recognized in 1897. Shortly 

 afterward my friend Mr C. A. Hart, of the Illinois State Laboratory of 

 Natural History, sent me a manuscript key in which these major divisions 

 were plainly indicated, and also a number of minor divisions, including the 

 tribes B a e t i n i and Caenini of Banks (Trans. Amer. Ent. Soc. 

 26:247. 1900). This key was then already in use by entomological stu- 

 dents at the University of Illinois, the basis for these divisions having 

 been recognized independently and, perhaps, prior to my own recognition 

 of them. 



