Diamesa caucasica Kownacki et Kownacka

Makarchenko, Eugenyi A., Semenchenko, Alexander A. & Palatov, Dmitry M., 2022, Redescription of the Caucasian endemic Diamesa caucasica Kownacki et Kownacka (Diptera: Chironomidae: Diamesinae), Zootaxa 5159 (3), pp. 445-450 : 446-449

Diamesa caucasica Kownacki et Kownacka

( Figs. 1–6 )

Diamesa caucasica Kownacki et Kownacka, 1973: 131 ; Ashe & O’Connor 2009: 272.

Material examined. RUSSIA: 3 adult males, Republic of North Ossetia — Alania, Irafsky District, North Caucasus , Urukh River , about 12 km from Mastocete Glacier , 03.I.2018, alt. 1829 m a.s.l., N 42.900183, E 43.585233 ; 5 adult males, the same locality, except Tanandon River, about 8 km from Tanancete Glacier , 03.I.2018, alt. 1718 m a.s.l., N 42.89535, E 43.604733 ; 3 adult males, the same locality, except Alagirsky District, Skazdon River, about 3.5 km from Skazsky Glacier , 27.VII.2019, alt. 1943 m a.s.l., N 42.784167, E 43.903667 ; 6 adult males, the same locality, except Tseydon River near Vertical Hotel , about 7.5 km from Tseysky Glacier, 07. V.2022, N 42.79266, E 43.92005 .

Description

Adult male (n = 6, except when otherwise stated). Total length 2.9–3.5 mm. Wing length

3.4–3.6 mm. Total length/wing length 0.83–0.92.

Coloration. Head, thorax and abdomen dark brown; legs brown to light brown; wings greyish, with brownish venation.

Head. Eyes bare and not extended dorsomedially. Temporal setae including 4–6 preoculars, 12–15 verticals and 11–12 postorbitals. Clypeus with 7–10 setae. Antenna with 13 flagellomeres and developed plume; terminal flagellomere without subapical setae; AR 1.0–1.22. Palpomere lengths (in μm) (n=2): 44–48; 80–84; 128–140; 144–152; 176–196. Palpomere 3 distally with sensilla capitata (diameter 16 μm). Palpomeres 1–5 length/head width 0.94–1.0.

Thorax. Antepronotum with 4–7 lateral setae. Acrostichals absent, dorsocentrals 7–12, prealars 4–6, scutellars 19– 29.

Wing. Length 3.4–3.6 mm; width 1.0– 1.08 mm. R and R 1 with 20–25 setae, R 4+5 with 2–3 setae. Costa extension 115–131 μm long. RM length/MCu length 3.0–3.6. Anal lobe developed, outline rounded. Squama with 21–26 setae, in 1–2 rows. VR 0.90.

Legs. Spur of fore tibia 64–72 μm long; spurs of mid tibia 60–64 μm and 52–60 μm; of hind tibia 44–52 μm and 84–88 μm long. Hind tibial comb with 14–15 setae. Length (μm) and proportions of leg segments are as in Table 1 .

Hypopygium ( Figs. 1–6 ). Tergite IX with 14–19 setae (32–56 µm long) from one side of anal point and located on protuberance ( Figs. 1, 3, 6 ). Anal point short (40–48 µm long) and naked, in lateral view slightly curved upwards ( Figs. 3–4 ). Laterosternite IX with 5–7 setae, 40–48 µm long.Transverse sternopodeme (TSA) trapezoidal ( Fig. 2 ), 56 µm high, 100 µm wide; TSA height/TSA width 0.56. Aedeagal lobe as in Fig. 2 , 140 μm long, weakly chitinized; phallapodeme sclerotized, 140–144 µm long. Gonocoxite 340–420 µm long; superior volsellae double, covered with setae, 28–36 μm long ( Fig. 2 ). Gonostylus 376–412 μm long, in basal third or half widened along inner margin and with wedge-shaped appendage directed at angle backwards, densely covered with long and fine setae; distal half or two thirds of gonostylus narrow and of the same width, covered with fine setae 28–40 μm long and ending in short megaseta, 8 μm long ( Fig. 5–6 ). HR 0.90–1.02.

Pupa described by Kownacki & Kownacka (1973) who recorded some information on larva too.

Ecology. Adult males were collected from snow, stones and bowlders near mountain rivers and springs located at 1402–1943 m a.s.l., with flow rate of 0.2–1.0 m/s, water temperatures 0.8–11°C, and mineralization of 37–65 ppm.

Remarks. D. caucasica belongs to the latitarsis group, from the representatives of which adult males differ in the structure of the hypopygium, namely, in the shape of the gonostylus and presence of a basal wedge-shaped appendage, as well as in the arrangement of setae of tergite IX on protuberances and in a short naked anal point at angle directed downwards.

In general, adult males from North Ossetia are similar to those of the original description (Kovnacki & Kownacka 1973), but specimens from our material have total length 2.9–3.5 mm, AR 1.0–1.22, dorsocentrals 7–12, while in males from Georgia total length 6 mm, AR 0.96, dorsocentrals 10–12. It should be noted that our redescription has been supplemented with a number of features which were absent in the original description.

Distribution. Known only from glacial streams of Terek River basin in Caucasus ( Figs. 7–10 ).

Figures

FIGURES 1–6. Adult male of Diamesa caucasica Kownacki et Kownacka. 1, hypopygium in dorsal view; 2, transverse sternapodeme, aedeagal lobes and superior volsellae; 3, tergite IX; 4, anal point in lateral view; 5, gonostylus; 6, hypopygium in lateral view.

FIGURES 7–10. Localities of Diamesa caucasica Kownacki et Kownacka. 7, Greater Caucasus, Urukh River, about 12 km from Mastocete Glacier; 8, Greater Caucasus, Tanandon River, about 8 km from Tanancete Glacier; 9, Greater Caucasus, Skazdon River, about 3.5 km from Skazsky Glacier; 10, Tseydon River, about 7.5 km from Tseysky Glacier (Photos by D.M. Palatov).