Diamesa kolyma Makarchenko, 2025

Makarchenko, E. A., 2025, DESCRIPTION OF DIAMESA KOLYMA SP. N. (DIPTERA: CHIRONOMIDAE: DIAMESINAE) FROM THE KOLYMA RIVER BASIN, RUSSIA, Far Eastern Entomologist 520, pp. 1-7 : 2-6

Diamesa kolyma Makarchenko , sp. n.

https://zoobank.org/NomenclaturalActs/ BD7A2D0F-1E06-4081-A8D5-171F854A0ADF

Figs 1–13

TYPE MATERIAL. Holotype – 1 pharate adult ♂ extracted from mature pupa, Russia: Magadan Region, Tenkinsky District, Natalkinskyi GOK, Geologicheskyi Stream ( Kolyma River basin), 61.6659°N, 147.8541°E, h= 838 m, 04.VIII. 2024, leg. A. Krasheninnikov. Paratypes: 2 pharate adult males, 4 mature pupae, 6 larvae, the same data as holotype .

DESCRIPTION. Pharate adult male (n=2). Total coloration brown to darkbrown; head, thorax, legs, and abdomen brown to dark brown; antennae light brown.

Head. Eyes bare and not extended dorsomedially. Temporal setae including 3 preoculars, 14 verticals, 10–11 postorbitals. Clypeus with 15 setae. Antenna with 13 flagellomeres and developed plume of setae; terminal flagellomere with 1 subapical setae, 40 μm long; AR 2.0–2.04. Palpomere length (μm): 40, 68, 88, 92, 140. Palpomere 3 in distal part with sensilla capitata with diameter ca 16 μm. Head width/ palpal length 1.57.

Thorax. Antepronotum with 7 ventrolateral setae. Dorsocentrals 8–9 (in 1 row), prealars 6–9, scutellars 36 (in 2–3 rows).

Wings and legs absent.

Hypopygium ( Figs 1–3 ). Tergite IX with 8–11 setae on each side and with anal point 196–200 μm long, 8 μm wide, with rounded apex ( Figs 1–2 ). Laterosternite IX with 9–10 setae. Transverse sternapodeme narrow, arcuate, 252 μm long. Phallapodeme 112 μm long. Gonocoxite 208 μm long; inferior volsellae large and wide, tapering slightly distally, covered with short setae, the longest subapically ( Figs 1–2 );

basimedial setae cluster absent. Gonostylus 160 μm long, slightly curved, covered with short setae, apical part angular-rounded, with megaseta 10 μm long ( Figs 1–3 ). HR 1.3.

Pupa (n=2). Total length 4.0– 4.2 mm.

Coloration. Сephalothorax dark brown, thoracic horn yellow, abdomen yellowish brown. Exuviae yellow.

Cephalothorax. Frontal apotoma with 2 setae 256–276 μm long. Thorax wrinkled, in anterodorsal and lateral parts granulated. Thoracic horn 361–416 μm long, filiform, with small spinules at the top. Precorneal setae lengths (μm): Pc 1 – 200–262, Pc 2 – 128–164 ( Fig. 4 ). Antepronotum with 2 median and 2 lateral antepronotals, 104–108 μm long. Mesonotum with 2 dorsocentrals: Dc 1 strong, 249 μm long, Dc 2 hair-like, 40 μm long.

Abdomen. Tergite I without shagreen and teeth. Tergites II–VII with shagreen in anterior third or half, tergite VIII almost all with shagreen. Sternites I–II without shagreen, sternites III–VIII with rare shagreen and IX without shagreen. Tergite I and sternites I–II without posterior transverse row of spines. Tergites II—VIII with spines of sternites III–VIII respectively – 10–11: 10: 12: 12: 8–9: 8–9 ( Figs 5–7 ). Segments I–2 with 2 pairs of lateral setae, 52–136 μm long; segments III–VII posterior transverse row spines, number of these spines on tergites respectively – 10–11: 10: 12: 12–13: 10: 8: 6 ( Figs 5–7 ). Number of posterior transverse row with 3 pairs of strong lateral setae, 112–148 μm long (L 1 –L 3) and 1 pair of hair-like setae, 52 μm long (L 4). Segments II –VIII with spine-like process on posterolateral corner. Anal lobe with 3 yellow anal macrosetae, 280–304 μm long, slightly curved in distal part and pointed. Male genital sac little extended beyond anal lobe ( Fig. 7 ).

Fourth instar larva ( n = 4). Total length 7.8–9.8 mm. Head capsule yellow, with brown or dark brown spots in basal half dorsally ( Fig. 8 ), 574–623 µm long and 377–410 µm width; postoccipital margin black and wide. SI and SII short and simple, SIII befurcate, hair-like. Labral lamellae consisting of 5 lobes. Premandible broad, apically with 7–8 teeth ( Fig. 12 ). Antenna with 5 segments, length of antennal segments (µm): 64, 16, 10, 3, 4. Lauterborn organs small; style reaches base of fourth segment; longest branch of antennal blade reaches the apex of the fourth segment; ring organ ca 6 µm diameter located in basal quarter of first segment ( Fig. 10 ); AR 1.77–1.94. Mandible dark brown to black, with apical tooth and 4 inner teeth; apical tooth slightly longer than the first inner tooth; seta subdentalis minute; seta interna with 24–26 simple branches ( Fig. 11 ). Mentum with 1 median and 9 pairs of lateral teeth; median tooth about the same size as the first and second lateral teeth or little wider and together with them below third pair of lateral teeth; ventromental plate small ( Fig. 9 ). Procercus dark brown, in the form of incompletely sclerotized ring, bearing 4 dark brown strong anal setae, 228–236 µm long and 1 hair-like lateral seta which is on the body, 64–68 µm long ( Fig. 13 ). Posterior parapods in 1.4 times as long as last body segment. Dorsal and ventral pairs of anal tubulus 136–172 µm long.

DIAGNOSIS. The male of new species is closely related to Diamesa bertrami Edwards but differs well from it in the shape of the gonostylus, size and shape of anal point and superior volsellae. Also, eyes of D. bertrami hairy and AR 1.53, while D. kolyma sp. n. with not hairy eyes and AR 2.0–2.04. The larva is most closely related to D. vernalis Makarchenko but the latter has yellow head without dark brown spots, like a new species. A similar spotting of the head is typical for the larvae of D. tsutsuii Tokunaga , but it has dark triangular spot in the clypeal region, while D. kolyma sp. n. without spot in this area.

DISTRIBUTION. Known only from type locality.

ETYMOLOGY. The species is named as kolyma after the type locality in the Kolyma River basin. The name is a noun in apposition.

Figures

Figs 1–2. Adult male hypopygium of Diamesa kolyma sp. n. in dorsal view.

Figs 3–7. Adult male (3) and pupa (4–7) of Diamesa kolyma sp. n. 3 – gonocoxite and gonostylus; 4 – thoracic horn and precorneal setae; 5 – tergite III; 6 – tergite V; 7 – tergite IX and anal segment. 4

Figs 8–13. Larva of fourth instar of Diamesa kolyma sp. n. 8 – head; 9 – mentum; 10 – antenna; 11 – distal part of mandible; 12 – distal part of premandible; 13 – procercus. Scale bars: 20 µm. 5