246 
Few records of the various described spe- 
cies occur in literature, and the general 
taxonomy of the group is far from satis- 
factory because of the lack of reared ma- 
NYMPHAL MANDIBLES 
NyMPHAL 
MAXILLA 
NyMPHAL 
HEAD AND 
THORACIC STERNITES 
Fig. 4.—Peltoperla brevis. 
terial and series of associated males and 
females, and because of certain weaknesses 
in existing specific descriptions. 
The character, number and location of 
the gills in the nymphs, and remnants of 
these in the adults, are certain to prove of 
ereat value in future work of identifica- 
tion. Claassen (1931) has given a good 
description of Peltoperla arcuata Need- 
ham nymphs based upon reared material. 
This nymph has five pairs of filamentous 
gills, one pair each side near upper point 
of attachment of each mesothoracic leg, 
one pair each side near upper point of 
attachment of each metathoracic leg, and 
one pair on the underside of the meta- 
sternum. Nymphs in the Illinois Natural 
History Survey collection which certainly 
belong to P. brevis (Banks), fig. 3, have 
Iutino1is NATURAL History SURVEY BULLETIN 
Vol. 22, Aria 
six pairs of gills, one pair near upper point 
of attachment of each leg and none be- 
neath the metasternum, fig. 4. These 
differences in number and arrangement of 
gills indicate the taxonomic value of these 
characters, and they need to be carefully 
observed in all species. Dorsal view of the 
nymph is illustrated in fig. 3. 
As in other adults whose nymphs have 
gills, the adults of Peltoperla show gill 
remnants when examined closely. I have 
noted, however, that adults of Peltoperla 
have membranous filaments on the dorsal 
thoracic segments which cannot be associ- 
ated with gills in the nymphs. ‘These false 
gill-like appendages appear to be rem- 
nants of membranous tissue, an appearance 
occasioned by the peculiar shieldlike tho- 
racic segments of the nymphs. 
Peltoperla arcuata Needham 
Peltoperla arcuata Needham (1905, p. 108). 
Original description, 2. 
Peltoperla arcuata Needham & Claassen 
(1925, p. 170). Description, ¢. 
This species was originally described 
from a female; the description of the male 
appeared later. Since the description of 
the male of this species by Needham & 
Claassen (1925) does not mention the 
peculiar shape of the anal cerci, | present 
three illustrations, fig. 5, which show their 
shape. ‘These illustrations are based upon 
a specimen from Ithaca, N. Y., in the 
Cornell University collection, recorded by 
Needham & Claassen (1925). The figure 
presented by these authors for the male 
ES 
Fig. 5.—Peltoperla arcuata. 
