September, 1942 
outer posterior corner of the submentum 
Is suggestive of an atrophied submental 
gill. No true submental gill. 
Nymphal and exuvial records are as fol- 
OWS. 
NorTH CAROLINA.—BALsAM: Same datteas 
for holotype, 4 nymphs, 9 exuviae. WILLETTs: 
March 23, 1940, T. H. Frison, C. O. Mohr & 
A. S. Hawkins, 6 nymphs. 
TENNESSEE.—ELKMONT, Little River: May 
14, 1939, Tl. H. Frison & H. H. Ross, 9 exuviae. 
GATLINBURG, Le Conte Creek: May 14, 1939, 
T. H. Frison & H. H. Ross, 2 exuviae. 
I have been able to associate the nymph 
of this species with its adult because of a 
mature male nymph which clearly shows 
the distinctive structural features of the 
adult about to emerge and which was col- 
lected at the same time and place as the 
holotype. The terminal abdominal struc- 
tures of the male are much different from 
those of any other species of this genus 
known to me. Among the Diploperla 
(s.J.), as 1 am now recognizing this genus, 
this new species differs from duplicata 
(Banks) and bilobata (Needham & Claas- 
Fig. 84—Nymph of Diploperla ee 
Frison: NortH AMERICAN PLECOPTERA 311 
sen) in the male in lacking the lobes on 
terminal abdominal sternites. It differs 
from another complex of species, including 
verticalis (Banks), in lacking the heavily 
sclerotized lateral  stylets flanking the 
supra-anal process. 
ISOPERLIDAE 
The family placement of the genus 
Isoperla presents several problems. Need- 
ham & Claassen (1925), following many 
other workers, have placed this genus in 
the family Perlidae, and there are several 
reasons for so doing. In my 1935a paper 
on Illinois stoneflies, I placed Isoperla in 
the family Chloroperlidae, chiefly because 
of its lack of gills in nymphs or of gill 
remnants in adults. In addition to having 
characters in common with the Perlidae, 
theseenusmisoperize (sd \ehasy characters 
also in common with the Perlodidae. 
It now seems desirable to me to erect 
a special family for this genus, rather than 
place it in existing families, Therefore, 
I propose the family name of Isoperlidae 
for the species now recorded under Tsoper- 
la (s.1.) and consider bilineata (Say), the 
type of the genus Isoperla Banks, as its 
most typical species. 
Isoperla holochlora (Klapalek) 
eras holochlora Klapalek (1923.05 p; 
LE 
Probably because of its late date of de- 
scription, holochlora was not included by 
Needham & Claassen (1925) in their 
Monograph; it was omitted by Claassen 
(1928) when additions and corrections to 
the Monograph were published. It is 
listed, however, in Claassen’s (1940) post- 
humously published Catalogue. 
Ricker (1938) in reporting upon his 
studies of the four cotypic series in the 
Musée Royal d’Histoire Naturelle, Brus- 
sels, Belgium, stated that one of these co- 
typic specimens is probably different from 
the others and selected a female as a lecto- 
type. In 1938, through the kindness of 
Dr. Victor Van Straelen, Director of this 
Museum, one of the male cotypes, which 
Ricker assumed to be of the same species 
as the lectotypic female, was sent to me 
for study. This male agrees well with 
Ricker’s description of the general features 
of the lectotypic female and was found to 
