1924] Male of the Partheno genetic May-Fly, Ameletus ludens 309 
curiously sculptured egg (Ann. Ent. Soc. Amer. 6: 400, PL 52, 
fig. 59, 1913); and she continued to rear the nymphs without 
finding a single male. I have myself, also, reared scores of 
nymphs — all females. Clemens examined hundreds of nymphs 
and found them all females. He demonstrated parthenogenesis 
by taking the eggs of these females, reared in isolation from 
males and unmated, and hatching them. He found the period of 
incubation to be five months (1. c., p. 78). 
I have recently come upon this same marked tendency 
toward parthogenesis in the genus Ephemerella. In the course 
of a biological survey of the Lloyd-Cornell Reservation near 
McLean, N. Y., made during the past summer, two species of 
this genus were collected, and the commoner one was represented 
only by females. Hundreds of nymphs were collected by Mr. C. 
K. Sibley and myself, and scores of these were reared in cages, 
and only females were found. As a nymph this species has long 
been known. I described and figured it in 1905 (as Ephemerella 
sp. N. Y. State Museum Bull. 86:45, PI. 10). It is widely dis- 
tributed in New York State. Since no males are to be had and 
there is no present prospect of obtaining materials for more 
adequately characterizing the species, it might as well bear a 
name, so I propose the name Ephemerella feyninina for it. I note 
that Dodds, in describing a similar Ephemerella nymph from 
Colorado (Trans. Amer. Ent. Soc. 49:99, 1923), says of it ‘^About 
thirty nymphs of this species in our collection include no males. 
Little is known as yet concerning unusual life cycles in the 
Ephemerida. The ovo-viviparous habit of the European 
Chloeon dipterum has long been known (See Lestage, Larves 
aquatiques des Insectes d’Europe, Yol. I, p. 250, 1921). Recently 
Miss Helen E. Murphy, on dissecting out the eggs from the 
ovaries of a female of a South American Callibaetis, discovered 
them to contain well grown embryos; wherefore, we named this 
new species Callihcetis viviparus (Lloyd Library Bull. 24: 50, 
PL XII, fig. 154, 1924). It is probable than much remains to be 
discovered on more complete studies of the life histories of the 
group. 
Cytologists. who gather females of Ameletus ludens for the 
study of chromosome behavior in development need to be re- 
