September, 1942 
from British Columbia which certainly 
belong to the genus Dictyopterygella. 
Since the only known western species of 
this genus is knowltoni, and since I am 
unable to separate these British Colum- 
bian females from ones here considered 
and described as the species knowltonti, 
I am identifying these specimens as of 
this species. The description of this pre- 
viously unknown nymph follows. 
NymMpPuH. — General color yellowish 
brown with black or fuscous areas as in 
fig. 73; labium, maxillae and mandibles 
asin fig. 72; bases of maxillae somewhat 
extending out from sides of head and visj- 
ble from above; subanal lobes prominent; 
no thoracic or anal gills; no distinct sub- 
mental gills present but at the point where 
such gills are present in Hydroperla or 
Isogenus there is a small, nipple-like pro- 
tuberance. Approximate length of mature 
nymph 18 mm. 
The nymphs upon which this descrip- 
tion is based were collected at “Shingle 
Creek, Penticton, British Columbia, April 
fe 733, ALN. (GG. and: ate -associated 
with two adult females from the same 
place collected on April 19, 1935, together 
with one adult female reared from nymph 
on May 1, 1935, and associated with jts 
exuvia. 
It is interesting to note that the first 
description of a nymph of Dictyoptery- 
gella, for the British species of bicaudata 
(Linnaeus), has only recently been pub- 
lished by Hynes (1941). The nymph of 
knowltoni agrees very closely with the 
nymph of bicaudata as described and 
figured by Hynes. 
Diploperla Needham & Claassen 
Diploperla Needham & Claassen (19252 Dp. 
286). New subgenus. 
In my paper on the Stoneflies, or Ple- 
coptera, of Illinois (1935a), I found it 
desirable to remove the genera Perlodes 
and Isogenus, and several species for which 
I proposed the generic name of Hydroper- 
la, from the family Perlidae and to place 
them in the family Perlodidae. This left 
a residue of North American species in 
the genus Perla (in the sense of Needham 
& Claassen 1925) which represented sey- 
eral distinct complexes of species, sub- 
genera or genera. The problem of the cor- 
rect use of the generic name of Perla and 
Frison: NortH AMERICAN PLECOPTERA 301 
the status of certain North American 
genera were not considered further in my 
1935 paper because that Paper was prima- 
rily a study of the Illinois species, not a 
monograph of the North American species. 
The description in this paper of new 
species of stoneflies from various parts of 
North America has now forced me to de- 
cide upon the use of certain generic names 
previously dodged. In my 19354 paper, I 
wrote, “Although Needham and Claassen 
#1925) thayem placed weeveral species of 
ieerias (ins thestbroad tsense as) used by 
them) in the subgenus Perla Geoffroy 
(s. str.) it is even doubtful whether the 
true Perla in the restricted sense as used 
by Klapalek (1923@) occurs in North 
America.” To get further data regarding 
thes status of Perla I wrote-in 1936 to 
Mr. D. E. Kimmons of the British Mu- 
seum requesting information about the 
genotype of Perla Geoffroy and its tax- 
onomic characters. Mr. Kimmons’ reply 
confirmed my previous suspicions and also 
added additional complicating data. Brief- 
ly, his report indicated (1) that the geno- 
type of Perla Geoffroy is Phryganea bi- 
caudata Linnaeus and not Perla bipunctata 
Pictet as selected by Klapalek (19232) or 
Perla maxima (Scopoli) as stated by 
Needham & Claassen Glee panda) 
that the name Perla probably should be 
associated with species now placed under 
another genus and family of stoneflies. 
Since this is a nomenclatorial problem 
primarily of concern to European ento- 
mologists, I am not assuming to settle the 
points involved at this time. 
However, in view of the probably er- 
roneous use of the generic name of Perla 
in European literature and the certainty 
that most, if not all, North American spe- 
cies placed in Perla in the past are not 
congeneric with the type of Perla, it is 
unwise to continue to describe new North 
American species under the generic name 
of Perla. 
Needham & Claassen (1925) listed 27 
species under the genus Perla in their tab- 
ulation of the North American stoneflies. 
Since then the number of species left 
standing unchallenged in Perla (sense of 
Needham & Claassen) has been reduced 
as follows: (1) a special genus Claas- 
senia Wu (1934) has been erected for 
languida (Needham & Claassen) notwith- 
standing that among the North American 
