September, 1942 
notum with a broad, median, longitudinal, 
yellow stripe, fig. 110; areas each side of 
stripe with brown to fuscous raised rugosi- 
ties. Mesonotum and metanotum brown 
with median dorsal area palest. Abdomen 
creamy yellow with sides brown to fus- 
cous. Legs, antennae and anal cercj brown 
to fuscous. 
Head wider through compound eyes 
than pronotum; ocelli forming an almost 
equilateral triangle, lateral ocellj much 
farther distant from one another than each 
is from inner margin of compound eye. 
Pronotum broader than long, approxi- 
mately quadrangular in shape, a distinct 
pattern of raised rugosities each side of 
median stripe, fig. 110. 
Legs with first and second tarsal seg- 
ments together shorter than third; first 
tarsal segment longer than second. 
Wings faintly tinged with brown; veins 
uniformly dark brown in forewings but 
some veins in anal area of hindwing very 
pale. 
Abdomen, fig. 110, with tenth tergite 
not cleft; subanal lobes weakly developed 
and not recurved over tenth tergite; ninth 
sternite produced backwards; eighth ster- 
nite with a prominent, rather broad lobe 
on middle of posterior margin, fig. 110. 
Length to tip of wings 11 mm.; length 
to tip of abdomen 9 mm. 
FEMALE.—Head, thorax, basal abdom- 
inal segments and appendages in general 
similar to those of male but slightly larger 
in size. Important differences are as fol- 
lows: eighth abdominal sternite, fig. 110, 
with subgenital plate well produced back- 
wards over ninth sternite and with tip 
slightly indented ; as viewed from the side 
the subgenital plate tends to extend down- 
wards away from abdomen. } 
Holotype, male. — Eddyville, Lusk Creek, 
Pope County, III: May 1, 1940, reared from 
nymph, B. D. Burks & C. O. Mohr. 
Allotype, female—Same data as for holo- 
type. 
Paratypes. — ILLINoIs, — EDDYVILLE: Same 
data as for holotype, 16. Same data as for 
holotype except dates of rearing as follows: 
May 5, 1940,1¢; May 7, 1940,28,19; May 
13, 1940, 19; May 15, 1940, 19; May 14, 
1940, 18, 39. 
NymPH.—General color pale creamy 
yellow with some pale brownish markings 
as in fig. 111. Legs, antennae and anal 
cerci pale yellow. 
Head with ocelli forming an almost 
Frison: NorrH AMERICAN PLECOPTERA 
333 
equilateral triangle, basal segments of 
mouthparts somewhat extending out be- 
yond sides of head. Labium, mandibles 
and maxillae as in fig, 110; second hook- 
like tooth at tip of each maxilla very 
strongly developed and extending at least 
two-thirds as far as primary or first tooth. 
Pronotum broader than long, with 
markings as in fig. 111. 
Abdominal tergites mostly pale creamy 
yellow with a narrow, fuscous, transverse 
band on posterior margin of each tergite 
NyYMPHAL 
MANDIBLES 
ADULT HEAD 
AND PRONOTUM 
Q SUBGENITAL PLATE 
as Bvene beh fe t= beds cf 4 
BS ABDOMINAL STERNI ES 5 OR a 
3 Asbo 
o' ABDOMINAL SEGMENTS 
Fig. 110.—Isoperla burksi. 
