Diamesa praecipua Saether et Willassen

Makarchenko, Eugenyi A., Semenchenko, Alexander A. & Palatov, Dmitry M., 2022, Taxonomy of Diamesa steinboecki group (Diptera: Chironomidae: Diamesinae) with description and DNA barcoding of new species. I. Subgroups steinboecki and longipes, Zootaxa 5125 (5), pp. 483-512 : 504-508

Diamesa praecipua Saether et Willassen

( Figs. 58–67 , 78 )

Diamesa praecipua Saether et Willassen, 1987: 200 ; Ashe & O’Connor 2009: 283.

Material examined. 7 adult males, INDIA: Himalayas, Uttarakhand Province, Chamoli District, Rishi Ganga River, right tributary of the Alaknanda River near of Badrinath Town , altitude 3128 m above sea level, N 30.740733, E 79.48875, 12.V.2018, leg. D. Palatov.

Description

Adult male (n = 5, except when otherwise stated). Total length 1.8–1.9 mm. Total length/wing length 5.79– 8.49.

Coloration. Head, thorax and abdomen dark brown. Legs brown to light brown. Wings grey or brownish grey ( Fig. 58 ).

Head ( Fig. 60 ). Eyes haired, reniform. Temporal setae including 0 frontals, 2–5 orbitals, 4–5 verticals and 7 postorbitals. Clypeus with 3–4 setae. Antenna with 7 flagellomeres and reduced plume of setae ( Fig. 59 ); number and length of these setae on 1–6 flagellomeres respectively: 4 (28–32 μm), 2 (24–26 μm), 2 (24–40 μm), 0, 0, 0; terminal flagellomere with 2 setae, 24–28 μm long in subapical and apical area. Length of 1–7 flagellomeres (μm): 92–96, 36, 32–36, 28–32, 28, 26–28, 104–108; AR 0.41–0.43. Antennal length/palpal length 1.33–1.35. Palpomere length (μm): 28–36, 40–44, 72–84, 50–52, 56–72. Palpomere 3 in distal part with sensilla capitata with diameter 16–20 μm. Palpomeres 1–5 length/head width 0.80–0.82.

Thorax ( Fig. 62 ). Strongly reduced. Scutellum fused with scutum. Antepronotum with 10–15 ventrolateral setae, 40–60 μm long. Dorsocentrals 4–5, 60–64 μm long in anterior half of mesonotum; prealars 2–3, 40–56 μm long. Scutellum with 8–11 setae.

Wing ( Figs. 61–62 ). Strongly reduced, speckled and without venation. Length 212–328 μm, width 100–104 μm. Wing membrane with 2–3 setae, 16–28 µm long.

Legs. Spur of front tibia 34–40 µm long. Spurs of mid tibia 36–40 µm and 36–44 µm long. Spurs of hind tibia 56–60 µm and 40–52 µm long. Hind tibial comb with 18–22 setae. Fore leg without pseudospurs on ta 1; mid leg with 10–11 pseudospurs on ta 1, hind legs with 12–14 pseudospurs on ta 1. Length (μm) and proportions of leg segments are as in Table 11.

Hypopygium ( Figs. 63–67 ). Tergite IX without anal point, with 7–16 pale setae from one side, 13–20 µm long; anal tergal bands Y– type ( Fig. 63 ); median tergal band 84–92 µm long. Laterosternite IX with 5–8 setae, 24–32 µm long. Transverse sternapodeme trapezoidal ( Fig. 65 ), length 52–64 µm and 144–208 µm wide in basal part. Aedeagal lobe weakly sclerotized, shape as in Fig. 66 . Gonocoxite 260–304 µm long, with grey rectangular superior volsellae covered by short setae ( Fig. 63 ); inferior volsellae absent. Gonostylus triangular, 168–176 µm long, along outer edge in middle with keel ( Fig. 67 ); megaseta in form of wide terminal spine 12–14 μm long, next to it there is tooth and two setae of approximately same length ( Fig. 64 ).HR 1.50–1.81.

Adult female was described by Saether & Willassen (1987).

Pupa and larva unknown.

Remarks. Adult male from our material collected in the Indian Himalayas at an altitude of 3128 m above sea level differs from the males of this species described by Saether & Willassen (1987) from an altitude of 5100–5600 m above sea level in small body sizes (1.8–1.9 mm), longer wings (212–328 µm), the presence of antenna with 7 flagellomeres, a smaller number of setae (7–9) on tergite IX, and a trapezoidal shape of the transverse sternapodeme. Total length of male D. praecipua from the original description 2.84–3.26 mm, wing length 169–195 µm, antenna with 6 flagellomeres, tergite IX with 55–69 setae, transverse sternapodeme triangular.

We consider differences in the structure of the males of these two populations as a result of individual variability associated with living at different altitude, although it is possible that these are different species and a new species is present in our material. To confirm this, it is necessary to compare these two populations at the molecular genetics level in future.

Ecology. Adult males were collected from stones and bowlders near water in mountain river and near waterfall, located at an altitude of 3128 m, at a flow rate of 0.1–0.8 m /s, with water temperatures 11°C. Previously, this species was known only from the original description of adults collected in Nepal Himalaya at an altitude 5100–5600 m above sea level, where imagines with vestigial wings walked on the surface of the glacier and in small cavities beneath it. The larvae lived in meltwater drainage channels beneath the ice and fed on blue-green algae and bacteria. Insects were active at temperatures as low as -16°C ( Koshima 1984, 1985; Saether & WIllassen 1987).

Distribution. Known only from high altitude of Himalayas ( Fig. 78 ).

Figures

FIGURES 58–67. Diamesa praecipua Saether et Willassen, male. 58, total view; 59, antenna; 60, head; 61, wing; 62, thorax; 63, hypopygium in dorsal view; 64, apex of gonostylus; 65, transverse sternapodeme; 66, aedeagal lobe; 67, gonostylus.

FIGURES 75–78. Type localities of Diamesa moubayedi sp. nov. (75), Diamesa zagrosica sp. nov. (76), D. steinboecki Goetghebuer (77) and D. praecipua Saether et Willassen (78). 75, glacial karstic spring, Sannyn Mount, alt. 2000 m a. sea l., Central Lebanon (photo by J. Moubayed); 76, Dare Daei River, Zagros Mountains, alt. 2244 m a. sea l., Lorestan Province, Iran (photo by D.M. Palatov); 77, Muttbach Stream, Valais Canton, Swiss Alps (photo by Jean–Louis Lods); 78, Rishi Ganga River, right tributary of the Alaknanda River near town of Badrinath, alt. 3128 m a. s. l., Himalayas, India (photo by D.M. Palatov).