Nixe rusticalis

Nixe rusticalis (McDunnough, 1931)

Larvae: Body length 6.0–8.5 mm; caudal filaments slightly shorter than body. General color brown with pale markings (Figs. 11–13). Head: Head capsule brown with two pale markings on anterior margin separated by distance less than distance between antennae bases, narrow pale streak extending from eyes to lateral margin of head capsule and occasionally another pair of pale markings directly posterior to marginal pale markings and small black spots often present near anterior margin; ocelli black with pale spot anterior to median ocellus and pale spot laterad of lateral ocellus. Mouthparts: Labrum (Fig. 14) ventrally with single row of 5–6 stout setae on either side of midline, anterolaterally with two rows of long, robust setae. Mandible with 4 setae at base of incisors. Hypopharynx with long setae on distal part of superlingua. Maxilla (Fig.15) with 16–18 comb setae apically, numerous scattered fimbriate setae on ventral surface of galealacinia; maxillary palp with numerous fine setae on base (Fig. 15), inner margin of first segment with numerous long setae. Thorax: Brown with pale markings. Forefemur pale with two chevron shaped bands, proximal band divided medially, with dorsal row of long setae, with ventral row of sharp robust setae and numerous spatulate setae approximately 3X longer than wide on anterior surface (Fig. 18); foretibia uniformly brown, with sparse row of fine setae on posterior margin and sparse fine setae on lateral ridge, 14-16 relatively long robust setae on anterior margin, 10-12 robust setae and scattered fine setae on inner surface; foretarsus brown, slightly darker apically, with row of long fine setae on posterior margin, sparse row of fine setae on lateral ridge, and 10 robust setae on inner surface; tarsal claws with single row of denticles (Fig. 17). Midleg similar to hindleg but with less numerous setae and no robust setae on lateral ridge of tibiae. Hindfemur similar to forefemur; hindtibiae (Fig. 16) with row of long fine setae and 4 long robust setae on posterior margin, with row of short fine setae and 6 long robust setae on lateral ridge, with 28 long sharp robust setae on anterior margin, and with 23 short-long robust setae on inner surface (distal robust setae fimbriate); hindtarsus with 15 fimbriate robust setae on inner surface, with row of fine setae on posterior margin, and with scattered fine setae on lateral surface; hindtarsal claw with single row of denticles. Abdomen: Terga 2-7 brown with pair of submedian pale marks, single posteromedian pale mark, one pair of sublateral pale marks, and pair of lateral pale marks (Figs. 11–12). Sterna (Fig. 13) 2–5 pale with lateral brown longitudinal streaks becoming larger on posterior segments, sterna 6–9 mostly brown. Gills cream, present on segments 1-7 and with fibrils present on gills 1–6. Caudal filaments brown with spines at articulations and numerous fine intersegmental setae.

Diagnosis and discussion. Larvae of N. rusticalis are identified by the combination of a single pair of pale sublateral spots on the abdominal terga (Figs. 11–12), long spatulate robust setae on the anterior face of the femora (Fig. 18),>15 comb setae on anterior margin of the maxillae (Fig. 15), and the large number of robust setae on the anterior margin of the tibiae (Fig. 16). The pale abdominal spotting is generally more conspicuous on female larvae than on males. Larvae were collected from small, high-gradient streams along the Manitoba Escarpment in eastern Saskatchewan. They were often sympatric with Ecdyonurus simplicioides (McDunnough, 1924a).

Material examined. CANADA:SK: 7 larvae, 3 reared males with exuviae (two on slides), 8 reared females (exuviae of one on slide), Creek around Km 65 of Hwy 9, 53°22'12”N 102°05'17”W, 23-VII-2001, JM Webb; 4 larvae (mouthparts of one on slide), Otosquen Creek at Hwy 9, 52°18'04”N 102°05'50”W, 9-VII-2001, JM Webb; 1 larva, Waskwei River at Hwy 9, 53°25'8”N 102°4'26”W, JM Webb, 23-VII-2001; 75 larvae (parts of 1 on slide), Waskwei River at Hwy 9, 53°25'8”N 102°4'26”W, ER Whiting, 8-VII-1980; 5 larvae (parts of one on slide), Rice River at Hwy 163, ER Whiting, 23-VI-1980. All material in JMW's personal collection.