LUCY WRIGHT SMITH 
475 
Six immature specimens from Goat Creek, Ashford, Washing- 
ton, (Miss Hortense Butler), XI, 12, 1905, in the entomological 
collection at Cornell University, Ithaca, New York. 
ARCYNOPTERYX Klapdlek 
1904. Arcynopleryx Klapdlek, Bull. Intern. Acad. Scien. Bohdme, no. 17: 7. 
1912. Arcynopleryx Klapdlek, Coll. Selys, 4: 13. 
In making a general statement concerning this genus, Klapdlek 
says that it is closely related in the character of the venation to 
Perlodes Banks, but is totallj' different from it in the structure 
of the genitalia. In the American species the apical network of 
cross-veins is irregular and restricted to the anterior part of the 
wing, it extends chiefly between costa and the branches of the 
radial sector; the costal margin shows a slight concavity at the 
humeral cross-vein; with the exception of Arcynopleryx aurea, at 
least the first third (often considerably more) of the area beyond 
the humeral cross-vein free from cross-veins; except in Arcynop- 
teryx vagans and aurea subcosta passes into radius before the 
level of the cord; the length of the inner, inter-radial cell at least 
twice as great as its base. 
In the male the ninth sternite forms a subgenital plate; the 
tenth tergite is bifid, the posterior inner margin of each lobe is 
prolonged into an appendage-like process which is directed dorsal- 
ward; the supra-anal plate consists of a pair of para-genital plates, 
and median and lateral stylets. In Arcynopleryx vagans, the only 
species of which we have a male, the para-genital plates are the 
only parts that are visible without dissection. 
Adults of some species of this genus are gill-bearing. 
With one exception, the new species which I am including in 
this genus are based on venational characters and are repre- 
sented only by females. 
Key lo Species of Arcynopleryx^ 
Adults 
a. Without tracheal gills. 
b. An apical network of cross-veins in the area between costa and the 
branches of the radial sector inornata 
bb. An apical network of cross-veins in the area between costa and media. 
Ignota 
* Arcynopleryx minor Klapdlek, from Arctic America, is omitted in this key, 
since it is unknown to me and since Klapdlek does not figure it. 
TRANS. .\M. ENT. SOC., XLIII. 
