MAY FJAFjH and MIDOKS OF NF'IW YORK 



41 



NaturaliHt vol. ^7, i)p.27-29, HKK',. Jl will he at once distin- 

 guished from all other genera by llie form of (he gill lamellae, 



Fl(f. 7 Oil) larnolliu; of the nymph of UlusturuH c; u p i d u 3 Hay; e, from tho Ist 

 aegment; i\ Ironi the 4tli .scKiriorit; K,'l«orri thcJtli.sc-Krneiit 



a figure of wlii'Ii is herewith given (fig.Tj. There are well-de- 

 V(,'loped lateral sj)ineH preH<?nt on ;ibdoniinal segments 8 and U 

 only. 



Ephemerella 



This is one of tlu* genera of 1] j> h (mh e i' i d a e that shows 

 grejit nymplial s[)ecijilization independently of adult life. The 

 nymphs are obviously very diverse in form and structure; the 

 iniagos vary much alike, or else their ditferences are easily over- 

 looked. Katon pointed out in his Monograph tlie remarkable 

 differences between the nynii»h which I have since bred and 

 shown in bulletin 47 to be that of E. e x c r u c i an s , and that 

 of the Pi]uro[>ean E. i gn i t a, the only bred sjKicies with which 

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

 named genus allied to E p h e m e r e 1 1 a; but it is the nymph 

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

 native species closely alJir-d to 1-]. i g n i t ii . I have compared 

 both nymphs and adults with E. e x c r u c i a n s . I have not 

 found differences that would seem to justify the generic wejiara- 

 tion of the images; and notwithstanding the evident differences 

 of the nymplis, T think they may as well, for the present, at 

 least, remain associated together under the one name. The 

 nymplijil differences are chiefly in the number and arrangement 

 of tlie gill lamellae, and these things are i>erhaps most subject 

 to tlie inflnenee of environment. 



