194 
[October 
almost exclusively founded. The extreme tip of the front wing in my 
specimen is not hyaline, as Dr. Hagen supposes. By the words “ ter¬ 
minal one-third of the wings dusky, until a definite outline,” I intend¬ 
ed to specify that the dusky part did not shade off gradually into the 
hyaline part. 
As only the % of nehulosus is at present known, it may possibly be 
the case that my specimen, which is deprived of all sexual characters, 
may be the 9 of that species ; and that the tip of the front wingjs being 
hyaline may be a mere sexual distinction of the % . Similarly in Pla- 
theniis trimaculata (Libellulina) the tip of the S front wing is hyaline, 
and that of the 9 front wing brown. And if, as both Dr. Hagen and 
myself think, Psocus abruptm and Ps. corruptus are the sexes of one 
species, we here have a subterminal hyaline semi-fascia, accompanied 
by a large discal hyaline spot, in % , and in 9 merely a subterminal 
hyaline fascia. But on the above supposition we cannot refer to nehu¬ 
losus the 6 doubtful 9 9 from Saskatchawan, described by Dr. Hagen 
under P. cupidus^ which have immaculate wings. 
Note 14, p. 172. All my seven specimens of P. cupidus subimago 
have the four posterior tarsi brown-black, except two where they are 
rather dusky than brown-black. My unique specimen of P. cupidus % 
imago was evidently an unusually small one, as becomes manifest from 
comparing the dimensions which I have given of the % subimago. 
Note 15, p. 173. As the wings of these six 9 9 are said to be hya¬ 
line, it seems contrary to analogy that they should be identical with a 
S which has the terminal 4 of its front wing brown. Dr. Hagen does 
not state whether they agree with the 9 P- concinnus from Washing¬ 
ton. The descriptions agree tolerably well, but unfortunately the length 
of the intermediate seta of P. concinnus is not given in the Synopsis. 
The proportion of the exterior to the intermediate seta (15 to 8) in the 
six doubtful 9 9 dilfers greatly from the proportion in my 9 cupidus 
subimago, (10 to about 8); but it seems to be the general rule in Ephe- 
merina, that as a species progresses from larva through pupa and subi¬ 
mago to imago, the proportional length of the middle seta should gradu¬ 
ally diminish. For example, in Ephemera Walsh, the middle seta 
of the imago is to the other setae as 14 to 20 % and 10 to 12 9; while 
in the sub imago the three are almost exactly equal. And it is well 
known that the genera with only two setae developed in the imago 
