Comprehensive Description

provided by Memoirs of the American Entomological Society
Isoperla sordida Banks
lsoperla sordida, Banks, 1906a, 38:337. Holotype $ ; Los Angeles Co., California, USA (MCZ #11,338) (male vesicle). Isoperla sordida, Banks, 1907a: 13.
hoperla sordida, Claassen, 1940, 232:206.
Isoperla sordida, lilies, 1966:420.
Isoperla sordida, Zwick, 1973:251.
Additional references: Isoperla sordida, Needham and Claassen, 1925 (male and female genitalia); Hoppe, 1938; Jewett, 1956, 1959, and 1960 (male and female genitalia); Gaufin, 1946b (in part); Knight et al., 1965b (ova); Gaufin et al., 1966 (in part, male and female genitalia); Newell, 1970; Gaufin et al., 1972 (in part, male and female genitalia); Ricker and Scudder, 1975; Baumann et al., 1977 (in part, male and female genitalia).
Male. — Macropterous. Length of forewings 9.0-10.4 mm; length of body 9.010.0 mm. General body color dark brown. Interocellar space of head dark brown, forming equilateral triangle between ocelli, 2 hook-shaped, narrow, dark brown bands extending toward clypeus; medium brown triangular band connecting lateral ocelli to occiput; light brown band extending from interocellar triangle to base of antennae and front of eyes (Fig. 220). Pronotum light brown, median yellow stripe, numerous vermiform, dark brown rugosities (Fig. 220). Wings flavescent, veins dark brown. Abdominal terga with 8 faint rows of longitudinal dots, 2 mesal, and 3 each laterally. Paraprocts thin, elongate, tapering to long, fine points apically; small, fine hairs scattered on upper surface, recurving over 1/4 10th tergum (Fig. 223). Cerci with one long, fine ventral hair at posterior margin of each segment. Vesicle elongate, narrow at base, rounded at apex, lighter than rest of segment (Fig. 221). Aedeagus with large dorsal lobe void of spinulae (Fig. 225D), with stout sclerotized process; dorsal arm bifurcate at tip, apex of each arm rounded and bearing row of small, stout spines (Figs. 222, 225E, & 226); anterodorsal margin produced into large lobe with dorsal patch of small, stout spinulae (Fig. 225C), smaller ventral lobe void of spinulae (Fig. 225 A), small median posterior lobe covered with small, stout spinulae (Fig. 225B); large patch of small, stout spinulae covering posterior and lateral aedeagus surfaces, extending along top half anterior lobe (Fig. 225C).
Female. — Macropterous. Length of forewings 10.5-13.1 mm; length of body 10.4-13.0 mm. General body color and head-pronotal pigment patterns similar to male. Subgenital plate indistinct, broad at base, evenly rounded posteriorly, with median shallow emargination, produced 1/4 length of 9th sternum (Fig. 224).
Nymph (described from female nymphal exuviae). — Length of mature female nymph 15-16 mm. Ocelli of head connected by band of dark brown pigmentation, band forming dark, equilateral triangle between ocelli, small light interocellar spot; wide, dark brown band extending from top of compound eyes and base of antennae to ocellar triangle; large "U"-shaped light area in front of anterior ocellus; occipital ridge bearing small, stout spinulae. Pronotum medium brown, median yellow stripe, 1 wide medium brown band, with variable light areas, bordering median stripe, margin fringe with short, stout setae, occasional long hairs interspersed at lower angles. Femora, tibiae, and tarsi with dorsal fringe of long, fine hairs, outer surface of femora with scattered spine-like setae, tibiae with ventral row of spine-like setae. Abdominal terga with 3 longitudinal stripes, 2 lateral and one mesal, and 8 faint rows of longitudinal dots, 2 mesal, and 3 each laterally. Posterior margin of cereal segments with whorl of small, stout hairs and one long ventral hair.
Ova. — General shape oval, cross section circular (Fig. 201). Color light brown. Length .32 mm; width .23 mm. Collar developed, expanded slightly at apex
with elevated ridges (Figs. 201 & 203). Chorionic ridges elevated, forming hexagonal cells, each with numerous, evenly spaced, small punctations (Figs. 201-203). Micropyles arranged 2 or 4 on top of distinct, elevated, transverse polar ridge, extending through hexagonal cells near bottom 1/3, on one side; raised, elongate sperm guides below each micropyle (Fig. 202).
Material examined. — TYPES: I. sordida, Holotype S, USA, CALIFORNIA: Los Angeles Co., Date ?, Hutchinson (MCZ #11,338). Additional specimens — USA — CALIFORNIA: Los Angeles Co., L. Elizabeth Can., 26/IV/1950, Collector ?, 1 3,1 9 (LCMNH); Trinity Co., E. C. Van Dyke, 2 J, 2 5 (CAS). MONTANA: Carbon Co., Rock Crk., Hell Roaring Crk., 29/VII/1966, J. R. Grierson, 1 $ (RWB); Glacier Co., Glacier Park, Siyeh Crk., 9/VIII/1963, Collector ?, 2 $ (RWB), Glacier Park, Siyeh Crk., 13/VIII/1963, Collector ?, 1 $, 1 9 (RWB), Waterton R., 23/VII/1970, C. Yarmoloy, 1 $ (RWB); Ravalli Co., 4.3 mi. above Hwy. 93, Chaffin Crk., 6/VII/1965, J. R. Grierson, 2 2 (UU), 1 mi. above Cameron Crk., Hart Crk., 23/VI/1965, J. R. Grierson, 1 $ (UU). OREGON: Deschutes Co., Fall R., 7/VI/1949, S. G. lewett and Morton, 13,19 (LCMNH), Fall R., 13/VII/1948, S. G. Jewett, 15 2, 10 nymphs (SJ); Jefferson Co., Wizard Falls, Metolius R., 19/LX/1949, L. E. Perry, 13,1? (RWB), Wizard Falls, Metolius R., bridge near clear lake, 7/IX/1965, S. G. Jewett, 1 9 (USNM); Sherman Co., Sheep Bridge, Deschutes R., 16/IX/1948, S. G. Jewett, 6 2,2 exuviae (CAS); Wallowa Co., Wallowa Mts., Lost Lake, 18/VIII/1952, K. M. Fender, 2 $, 2 9 (CAS), Crawfish Lake, trail above Anthony Lake, 12/VIII/1972, K. M. Fender, 13,29 (CAS), Lake Crk. Camp, Lastine R., 19/VIII/1952, K. M. Fender, 3 $ Distribution. — CANADA: British Columbia; USA: California, Montana, Oregon and Washington (Fig. 152).
bibliographic citation
Szczytko, S.W., Stewart, K.W. 1979. The genus Isoperla (Plecoptera) of Western North America; Holomorphology and Systematics, and a new Stonefly genus Cascadoperla. Memoirs of the American Entomological Society vol. 32. Philadelphia, USA