MAY PLIES AND MIDGES OP NEW YORK 41 



Naturalist vol. 37, pp.27-29, 1903. It will be at once distin- 

 guished from all other genera by the form of the gill lamellae, 



Fig. 7 Gill lamellae of the nymph of Blast ur us cupidus Say; e, from the 1st 

 segment ; f , from the 4th segment ; Tg, from the Jthjsegment 



a figure of which is herewith given (fig.7). There are well-de- 

 veloped lateral spines present on abdominal segments 8 and 9 

 only. 



Ephemerella 



This is one of the genera of Ephemeridae that shows 

 great nymphal specialization independently of adult life. The 

 nymphs are obviously very diverse in form and structure; the 

 imagos very much alike, or else their differences are easily over- 

 looked. Eaton pointed out in his Monograph the remarkable 

 differences between the nymph which I have since bred and 

 shown in bulletin 47 to be that of E. excrucians, and that 

 of the European E. i g n i t a , the only bred species with which 

 he was acquainted. He referred to this nymph a a new un- 

 named genus allied to Ephemerella; but it is the nymph 

 of the typical species. I describe herein the nymphs of two 

 native species closely allied to E. i g n i t a . I have compared 

 both nymphs and adults with E. excrucians. I have not 

 found differences that would seem to justify the generic separa- 

 tion of the imagos; and notwithstanding the evident differences 

 of the nyniphs, I think they may as well, for the present, at 

 least, remain associated together under the one name. The 

 nymphal differences are chiefly in the number and arrangement 

 of the gill lamellae, and these things are perhaps most subject 

 to the influence of environment. 



