302 
species languida 1s morphologically per- 
haps the closest representative of the genus 
Perla as now—but probably erroneously— 
used in Europe (sense of Klapalek 
1923a) ; (2) the recognition of Togoperla 
and Neophasganophora as valid North 
American genera (Frison 1935a) removed 
immarginata (Say), media (Walker) and 
capitata (Pictet) from the lists (3) othe 
erection of the genus Hydroperla (Frison 
1935a) removed the names of crosby1 
(Needham & Claassen) and varians 
(Walsh); (4) the placement (Frison 
1935a) of duplicata (Banks) in the genus 
Isoperla; and (5) the placement of kan- 
sensis (Banks) in Togoperla (Frison 
1937) removed an additional species. 
In this paper the list is further reduced 
as follows: (1) Perla sabulosa Banks is 
placed in the genus Acroneuria, and A. 
depressa Needham & Claassen is shown to 
be a synonym of it; (2) Perla postica 
Walker is considered to be unrecognizable 
at present and subvarians (Banks), be- 
longing to the genus Hydroperla, is the 
name to be associated with some at least 
of the Needham & Claassen records given 
under the name postica. 
It is quite evident from my studies to 
date that the species now left in Perla, 
some of which may later fall in synonymy, 
constitute several complexes or species 
groups, represented by such divergent 
forms as modesta Banks, luctuosa Banks 
and bilobata Needham & Claassen. It is 
highly probable also that one or two of 
these species will in the future be shifted 
to such genera as Isoperla or Hydroperla, 
since their generic relationships are some- 
what obscured now because of the poor 
condition of the types and the lack of other 
material which can be definitely associated 
with these names. Until these species are 
better known, however, it seems advisable 
to record them all under a single generic 
name. 
In view of the fact that it now seems 
unwise to use the generic name of Perla 
for these species, and for the two new 
species described in this article, the prob- 
lem of selecting a generic name is present- 
ed. It is now my belief that the species 
duplicata placed by Banks in Perla should 
not be included in Isoperla, as I proposed 
in 1935, and that it is more closely related 
to the species group represented by modes- 
ta Banks. This realignment of duplicata 
Itttrnois NaturAL Hisrory SURVEY BULLETIN 
Vol. 22, Arta 
with such species as modesta, and my pres- 
ent belief that the species now under dis- 
cussion should be grouped as a unit until 
they are better known, make possible the 
use of the name Diploperla Needham & 
Claassen (1925) for these species, since 
Diploperla was proposed for the species 
duplicata and bilobata. This action is ad- 
vantageous in that it makes possible the 
use of a name already in literature and 
removes the controversial name of Perla. 
Therefore, until additional information 
warrants other generic treatment, I pro- 
pose to group under the generic name of 
Diploperla Needham & Claassen (si 
the species described under the following 
names: Perla innubila Needham & Claas- 
sen, Perla alameda N. & C., Perla expansa 
Banks, Isogenus hastatus Banks, Perla 
fugitans N. & C., Perla nona N. Oot 
Perla aestivalis N. & C., Perla modesta 
Banks, Perla verticalis Banks, Perla tine- 
tata Claassen (nom. nov. for tincta N. & 
C.), Perla sorpta N. & C., Dictyogenus ? 
phaleratus Smith, Perla misnoma Clsn. 
(nom. nov. for obscura N. & C.), Perla 
errata Clsn. (nom. nov. for venosa N. & 
C.), Perla bilobata N. & C., Perla dupli- 
cata Banks, Perla luctuosa Banks and 
Perla ramosa N. & C. I am also assigning 
to this genus three new species described 
in this article. 
Since Needham & Claassen (1925) did 
not select a genotype for Diploperla, I 
designate the species hitherto known as 
Perla bilobata Needham & Claassen as 
the genotype because it is one of the two 
originally included species. 
The proper family placing of this genus 
has many puzzling aspects. The cleft 
tenth abdominal tergite, supra-anal proc- 
ess and associated structures in the male, 
as well as the wing venation and other 
features of both sexes, suggest a close re- 
lationship with Hydroperla. Lack of dis- 
tinct submental gills is annoying from 
the standpoint of a family key character, 
but there is a suggestion of these sub- 
mental gills in the small nipple-like pro- 
tuberance where a long submental gill is 
present in other genera of this family. 
Diploperla bilobata 
(Needham & Claassen) 
| 
Perla bilobata Needham & Claassen (1925, 
p. 95). Original description, 6, @. 
