Clastobasis subalternans sp.n.

Figures 1–4

Type material. Holotype male: RUSSIA, E Kunashir I., Filatovka River, 30–31.VII.2014, Y. Sundukov leg. (ZMUM).

Paratypes: 2 ♂♂, data as holotype (ZMUM).

Description. Male. Body length 5.3–5.5 mm. General colouration yellow.

Head. Yellowish brown. Three ocelli; with a black spot surrounding each lateral ocellus. Clypeus yellow. First palpomere and base of second palpomere brown, remainder of second palpomere yellow. Antenna bicoloured. Scape and pedicel yellow. Apical segments of flagellum brown. Sixth flagellomere two times as long as wide.

Thorax. Mesonotum yellow with three brownish stripes. Base of scutellum and mediotergite dark brown. Anepisternum and preepisternum 2 light brownish. Laterotergite with dark brown lower margin. Scutellum with 4 strong bristles. Laterotergite with long setae.

Wings. Faintly yellowish with yellow veins. Wing length 4.6–4.7 mm. Costa ends at tip of R5. Crossvein rm about 1.5 times as long as stem of median fork. Anterior branch of cubital fork interrupted at base. Halter yellow.

Legs. Yellow, hind femora with dark brown apical spots. Fore basitarsus as long as fore tibia. Middle tibia with 6–7 strong anterior setae, 1–3 shorter dorsal setae, 7–10 strong posterodorsal setae, 13–15 posterior setae, 10–12 ventral setae and 4–6 anteroventral setae. Hind tibia with 8–10 strong anterodorsal setae, 7–10 posterodorsal setae, 7–8 ventral setae, 5–6 anteroventral setae.

Abdomen. Yellow. Tergites I–V with dark brown bands. Tergite VI yellow. Tergites VII, VIII dark brown.

Terminalia. Brownish. Cerci yellow, long and narrow (fig. 1). Gonocoxites with deep narrow emargination in lateral view (fig. 2) and with small emargination ventrally (fig.3). Gonostylus broad basally (fig. 4).

Female. Unknown.

Biology. Unknown.

Etymology. The species’ name indicates the new species resemblance to C. alternans (Winnertz, 1863).

Comments. C. subalternans is most similar to C. alternans (Winnertz, 1863). The ventral appendage of the gonocoxite of the new species widens apically with a narrow emargination in lateral view (evenly tapering with broad emargination in C. alternans (Chandler, 2001: fig.17). Gonocoxites in ventral view with a small medial emargination (absent in C. alternans (Chandler, 2001: fig. 15).