Palzxarctic Nemoure. 569 
may bea good species but more material is required. On 
account of the immaturity of the ¢ the figures are not 
satisfactory. 
Nemoura marginata. 
N. marginata, Pictet, Mém. Soc. Phys., tom. vii., 
p. 181, No. 7; and Perlides, p. 397 (?). 
N. humeralis, Pictet, Mém. Soc. Phys., tom. vii., 
p. 184, No. 11; and Perlides, p. 399 (°?). 
Head and pronotum shining blackish, mixed with brown especi- 
ally on the hind-head. Pronotum slightly narrower than head ; 
borders not well defined, usually paler, the lateral margins recede 
very slightly posteriorly. Legs pale brown. Wings usually 
brownish, sometimes suffused, in other examples nearly hyaline, 
neuration darker especially in the region of the pterostigma and 
x nervures. The structure of the genitalia is complicated ; the 
paired sheaths are in this species much as in N. J/eyeri, but instead 
of ending in a simple acute point the apex is crowned by two short 
spines, and there appears to be another spine at some distance from 
the apex. The strong upright pieces are flanked by a chitinous 
sheath which is deeply pectinate, although the pectinations may 
sometimes be so closely appressed that they are difficult to see. 
Exp., 18-22 mm. 
In applying to this species the name of marginata, 
Pictet, I have been guided chiefly by the fig. of that 
author which agrees tolerably well with a common 
brownish Swiss insect. The limits of the species are, 
however, difficult to define, and there is a certain con- 
fusion regarding it and N. humeralis, a species not yet 
elucidated to my satisfaction. Professor Klapalek sent 
me a ¢ agreeing very well with Pictet’s description of 
N. humeralis, and also forwarded drawings of what he 
considered the ¢, but in the great number of examples 
examined by me I have not yet seen a ¢ which agreed 
with Klapalek’s ¢, and I am inclined to consider the 
latter as a condition of the species under review. In the 
rich materials forwarded by Dr, Ris, I found three forms 
which I have in the meantime referred here; the first 
series is from Glarus, in October, headed by a ¢, from 
which figs. 1 and 2 are taken; the females of this series 
have the wings comparatively transparent with rather 
strong neuration. ‘The second series mainly from the 
Ziirichberg in June have the wings more suffused and 
TRANS. ENT, SOC. LOND. 1894.—paRtiv. (DEC.) 20 
