Acnemia sibirica Ostroverkhova, 1979

Subbotina, Elena, Maksimova, Yulia & Polevoi, Alexei, 2024, The return of the forgotten: redescription and new data on the distribution of Acnemia sibirica Ostroverkhova, 1979 (Diptera: Mycetophilidae), Zootaxa 5432 (1), pp. 133-138 : 134-137

Acnemia sibirica Ostroverkhova, 1979

( Figs. 3–14 )

Acnemia sibirica Ostroverkhova, 1979: 93 , fig. 20: 4

Lectotype. Slide 610 ( Fig. 3 ): 1 ♂, Russia, Tomsk Province, lower River Tom’, near the Orlovka village , 28.VIII.1968, leg. S. Yuzhakova ( TSU).

Paralectotypes. Slide 611 ( Fig. 4 ): 1 ♂, same data as for lectotype ( TSU). Slide 883: 1 ♂, Russia, Irkutsk region, near the Bodaibo village , 28.VIII.1971, leg. O. Shimina ( TSU) .

Other material. 1 ♂, Russia, Tyva Republic, Todzhinsky district, Toora-Khem , 52.472°N, 96.109°E, 30.VIII.2017, leg. Sh. Dongak ( TSU) . 1 ♂, Russia Tyva Republic, Todzhinsky district, Ii , 52.548°N, 96.049°E, 6.IX.2018, leg. Sh. Dongak ( TSU) . 1 ♂, Russia, Sakhalin, Nevelsk District, Shebunino , 46.42°N, 141.87°E, Malaise trap, 21–24.VII.2009, leg. A. Humala ( FRIP) .

Diagnostic characters. Acnemia sibirica is most similar to A. longipalpis Zaitzev, 2006 , but distinguished by a longer outer lobe of the gonostylus as well as characters of the aedeagal complex, especially parameres, which are characteristically bent and irregularly serrated apically (clavate, with a brush of denticles in A. longipalpis ). Acnemia sibirica also resembles A. amoena Winnertz, 1864 , and A. ussuriensis Zaitzev, 1982 , by the shape of tergite 9, but clearly differs by other characters of male terminalia.

Description. Male.

Head. Frons and vertex yellowish brown; ovate patch around ocelli dark brown. Face and clypeus yellow. Three ocelli almost in line; lateral ocellus placed ca. 3x its diameter from eye margin. Postocular setae black. Palpus yellow, four segmented, about as long as antenna; fourth segment significantly elongated, almost twice as long as segments 1–3. Antenna yellow; middle flagellomeres about as long as wide.

Thorax. Scutum yellow with three dark longitudinal stripes and yellow setae. Pleural sclerites yellowish brown; laterotergite and mediotergite slightly darkened, with yellow setae. In specimen from Sakhalin scutum and pleural sclerites entirely yellow. Scutellum yellow with four yellow marginal setae.

Wings. Length 2.75–2.85 mm. Membrane with micro and macrotrichia. Sc ending in C (in one wing of paralectotype, slide 883, Sc not reaching C); cross-vein sc–r proximal to Rs. Costa produced beyond apex of R5 for about 1/4 of the distance between R5 and M1. Anterior fork long, divergent (in one wing of paralectotype, slide 883, base of vein M2 not developed). Stem of anterior fork 1.5x longer than r-m. M4 not developed. All veins, except sc-r and Rs with macrotrichia. Halter yellow.

Legs yellow. Fore coxa darkened at base (completely yellow in specimen from Sakhalin), mid and hind coxae darkened on extreme apex; trochanters darkened ventrally. Ratio of basitarsus to tibia for fore, mid and hind leg: 0.86–0.88; 0.65–0.70; 0.52. Fore tibia with av spur, mid and hind tibiae with av and pv spurs. Fore tibia with 0–2 p and 1–3 pd; mid tibia with 4–5 ad, 2–3 pd, 3 p, 4 pv; hind tibia with 8–9 ad, 4–6 d, 5–6 pd, 6 p.

Abdomen yellow. Tergites 2–5 with brown preapical transverse patches. Abdominal setae yellow.

Terminalia ( Figs. 5–14 ) yellowish brown. Dorsomedial part of gonocoxites shaped as rounded projection ( Fig. 5 ). Gonocoxites separated ventrally, with wide projections, suddenly narrowed into sharp apex, and bearing group of short setae on inner surface ( Figs. 6; 7 ). Tergite 9 rectangular, about twice wider than long, with two widely separated apical setae placed on slightly projecting outgrowths ( Fig. 8 ). Outer branch of gonostylus long, arcuate apically, ( Figs. 5 ; 9; 10 ); inner branch hammer shaped, with longer, hairy dorsal lobe and short membranous ventral lobe ( Fig. 10 ). Aedeagus bifid; parameres long, dorsally with two medially directed projections, at base and in the middle; strongly curved above upper projection; apices widened and irregularly serrated ( Figs. 11–14 ).

Taxonomic remarks. The identity of the species can be reliably established based on the illustrations by G.P. Ostroverkhova and on preserved slides with male terminalia. We could not locate a type specimen of Acnemia longipalpis in the collection where it was supposed to be stored, so a direct comparison was not possible. Though A. Zaitzev does not mention A. sibirica in the diagnosis, differences in the aedeagal complex are well visible in the original figure ( Zaitzev 2006, p. 2, Fig. 2 ).

Distribution. East Palaearctic: West Siberia and Sakhalin.

Habitat and biology. Mixed forest ( Ostroverkhova, 1979), mixed Larix and Betula forest, mixed Larix and Picea forest on the river bank (Tyva), young deciduous forest (Sakhalin). Larval microhabitat unknown.

Figures

FIGURES 1–4. Acnemia sibirica; 1, original material on slides (syntype specimens designated by red arrows); 2, original illustration by G.P. Ostroverkhova on card; 3, male terminalia, ventral view (lectotype, slide 610); 4, male terminalia, dorsal view (paralectotype, slide 611).

FIGURES 5–8. Acnemia sibirica, male terminalia; 5, dorsal view; 6, ventral view; 7, caudal view; 8, tergite 9. Scale bars: 0.2 mm. Abbreviations: dmp—dorso medial projection of gonocoxite, vp—ventral projection of gonocoxite, obg—outer branch of gonostylus.

FIGURES 9–14. Acnemia sibirica, male terminalia; 9, gonostylus, internal view; 10, gonostylus, caudal view; 11, aedeagus, dorsal view; 12, aedeagus, lateral view; 13, aedeagus, ventral view; 14, apex of paramere. Scale bars: 0.2 mm (Figs. 9–13), 0.1 mm (Fig. 14). Abbreviations: obg—outer branch of gonostylus; ibg—inner branch of gonostylus; par—paramere.