Diamesa saetheri Willassen, 1985

Makarchenko, Eugenyi A., Semenchenko, Alexander A. & Palatov, Dmitry M., 2022, Taxonomy of Diamesa steinboecki group (Diptera: Chironomidae: Diamesinae) with description and DNA barcoding of known species. II. Subgroups davisi, leona and loeffleri, Zootaxa 5190 (3), pp. 361-392 : 366-369

Diamesa saetheri Willassen

( Figs. 12–15 )

Diamesa saetheri Willassen, 1986: 120 ; Ashe & O’Connor 2009: 283.

Diamesa davisi auct., nec Edwards 1933. Pagast 1947: 477, 525, Figs. 37 , 79; Saether 1968: 441–444; Makarchenko 1980: 80, Figs. 1–2 .

Material examined. RUSSIA: 5 adult males, Chukotka Peninsula, The Gilmimliveem River in the area of thermal mineral springs of the Ioni Lake basin., 4.VIII.1973, leg. I. Levanidova ; 5 adult males, the same data, except for the surroundings of the Uelen Village, Nevidimka Stream , 12.VIII.1973, leg. I. Levanidova ; 5 adult males, Chukotka, Wrangel Island, Somnitelnaya River , 23.VII.1978, leg. E. Makarchenko ; 5 adult males, Magadan Region, Tenkinsky District, neighborhood of Sibit-Tyellakh Village, spurs of the peak Vlastny , Olen’ Stream ( Kolyma River basin), alt. 1300–1400 m a.s.l., 12–17. VI.1978, leg. Е. Makarchenko.

Description

Adult male (n = 20). Total length 2.60–3.25 mm. Total length/wing length 1.04–1.49.

Coloration. Dark brown to black; wing grayish, veins yellowish brown.

Head. Eyes hairy. Temporal setae including 0–1 orbitals, 9–15 verticals and 2–6 postorbitals. Clypeus with 4–8 setae. Antenna with 8 flagellomeres and reduced plume of setae 20–50 μm long. Flagellomeres 1–8 length (μm): 88–126, 34–50, 29–46, 29–36, 25–38, 25–34, 34–42, 88–126; terminal flagellomere with 1–2 subapical setae, 12–20 μm long and with 3–4 setae basally, 36–40 μm long; AR 0.28–0.38. Palpomeres lengths (in μm): 32–40; 46–76; 80–109; 71–101; 113–143. Palpomere 3 in distal part with sensilla capitata with diameter 14–16 μm. Antennal length/palpal length 1.12–1.46.

Thorax. Antepronotum with 8–11 ventrolateral setae. Dorsocentrals 7–12, prealars 2–6, scutellars 11–24.

Wing. Length 2.34–2.91 mm, width 0.72–0.93 mm. R and R 1 with 6–16 setae; R 4+5 with 2–7 setae in distal part. RM/MCu 2.0–3.2. Anal lobe rounded, often reduced. Squama with 19–21 setae.

Legs. Spur of front tibia 20–38 μm long; spurs of mid tibia 29–50 μm and 27–50 μm long; of hind tibia 20–63 μm and 51–126 μm long. Hind tibial comb with 14–21 setae. Lengths and proportions of leg segments as in Table 4 .

Hypopygium ( Figs. 12–15 ). Laterosternites well extended beyond posterior margin of tergite IX. Tergite IX with weak setae along gently rounded posterior margin; tergite bands Y-shaped ( Figs. 12–13 ); anal point reduced, not visible in dorsal view, angled downwards, without microtrichia ( Fig.14 ), 11–25 μm long; ratio of anal point length to gonostylus length 0.07–0.12. Gonocoxite massive, inner side densely covered with microtrichia and short setae, superior volsella with microtrichia and some short setae. Gonostylus weakly curved with 3–5 apical teeth and megaseta which in form of wide terminal spine ( Fig. 15 ). HR 1.77–2.50.

Pupa and larva were described by Saether (1968).

Remarks. Before the revision of the Diamesa davisi group by Willassen (1986) we identified this species as D. davisi Edwards. D. saetheri and D. davisi are very close related morphologically and possibly belong to the same species. To clarify the relationship of these two species, it is necessary in the future to obtain molecular genetic data for D. davisi from the type locality. Before this we adhere to Willassen’s position on taxonomy of these species. Males from Wrangel Island and the Kolyma River basin are slightly larger than those from other regions, but the leg indices and other data are similar for all populations ( Table 5 ). The most interesting specimens are from the highlands of the Kolyma River basin. In two out of five males the wings were noticeably reduced. The ratio of total length to wing length is 1.32–1.49, anal lobe reduced, and wing veins are indistinct. A similar reduction was noted earlier for D. steinboecki Goetghebuer ( Serra-Tosio 1974) and D. serratosioi Willassen ( Willassen 1986) .

Distribution. Known from Norway and Russian Far East (Chukotka Peninsula, Wrangel Island and Kolyma River basin).

Figures

FIGURES 8–15.Adult males of Diamesa amplexivirilia Hansen from Chukotka Region (8–11) and Diamesa saetheri Willassen from Chukotka Region (12–15). 8–9, 12–13, hypopygium in dorsal view; 10, 14, anal point in lateral view; 11, 15, apical part of gonostylus. Figs. 9–11, 13–15 after Makarchenko (1980).

FIGURES 29–38.Adult male of Diamesa leona Roback from Sakhalin Island (macropterous form) (29–31), Primorye Territory (brachypterous form) (32, 35–36), Chukotka (macropterous form) (33, 38) and Kamchatka (macropterous form) (34, 37). 29, typical normal hypopygium in dorsal view; 31, abnormal hypopygium in dorsal view; 30, 36, 37–38, gonostylus; 32–34, tergite IX (bent out on slide); 35, anal point in lateral view. Figs. 32–38 after Makarchenko (1981).

FIGURES 1–7. Adult male of Diamesa alpina Tokunaga from Sakhalin Island (1–2), Magadan Region (3), Chukotka (4), Khakassia (5), Alaska (6) and Canada (7). 1, anal point in lateral view; 2–3, 6–7, hypopygium in dorsal view; 4, antenna; 5, transverse sternapodeme and superior volsellae. Figs. 1–2 after Makarchenko (1980).