Protonemura bifida Martynov, 1928

(Figs. 1-6)

Protonemura bifida Martynov, 1928:22.

Holotype ♂ (Zoological Institute, Russian Academy of Science, St. Petersburg), Caucasus, Gvilety.

Material examined. North Ossetia, river Kharves basin (Uruch basin), 17 VII 2006, 4 larvae of male, 3 larvae of female (L. Haseeva leg); North Ossetia, river Unaldon (Ardon basin), 25 V 2000, 5 larvae (S. Cherchesova, M. Shioloshvili leg); Borshomy reservation, river Likanis - chevi; 7 V 1986, 3 larvae (L. Zhiltzova leg.).

Larva. Length of body (maximal) 7.5- 9 mm, length of cercus equal to length of abdomen and postnotum. Larva stocky, blackish – brown, mat, head darker than pronotum. Pronotum slightly wider than head; temporal part of head slightly projecting behind eyes and bearing a cluster of setae (Fig. 1).

Pronotum trapezoid, slightly narrowed backwards, with rounded angles; margins with dense row of rather long sharp setae (Figs. 3-4); setae longer and more numerous on angles; some setae shorter and more blunt on anterior margin.

Pronotal gills rather long, with contraction in apical part.

Legs: femur margined with coarse setae along upper border; tibia with dense strong bristles along upper and lower edge.

Abdominal segments 1–4 (or 1–5) divided on tergite and sternite (division unclear).

Setae on tergal surface are very short, dense (Fig. 5). Two long setae protrude on hind margin of abdominal tergites; other setae are very short and dense.

Sternite 9 of mature nymph of male medially triangularly elongated. Male paraprocts elongated and narrowed apically.

Sternite 8 in female larvae with small arched excavation (Fig. 2). In mature larva, contour of subgenital plate is seen.

Cerci with 22 – 23 segments armed with dense short and stout apical setae (Fig. 6); surface of segments densely covered with clothing setae. Length of segments 5 – 7 equals their width. Basal segments of cerci very short and wide, distal segments slender and very elongated.

Diagnosis. The larva of P. bifida differs most conspicuously from the three European species described by Lillehammer (1988) in cercal setation. Each of those species [P. hrabei Rauser, P. intricata (Ris), P. meyeri (Pictet)] have mixed setal types in the terminal segmental whorls for basal cercal segments whereas these setae are rather uniform in length in P.bifida (Fig. 6).