Plesioaxymyia imprevista Polevoi 2025, sp. nov.

Plesioaxymyia imprevista Polevoi sp. nov. Figs 2 A – C, 3 A – C Specimens examined. Holotype. Russia • ♀; Karelia, Paanajarvi National Park, Vartolambina; 66.246°N, 30.555°E; 80 m a. s. l.; 1–27 Jun. 2021; A. Protasova leg.; Malaise trap; GenBank: accession numbers PV 036313, PV 036316, PV 036319, PV 036317, PV 035246, PV 037681; ZISP, INS_DIP_0001011. Differential diagnosis. Medium-sized, dark brown species (Fig. 2 A); wings hyaline with dark elongated pterostigma, covering apical half of vein R 1; legs yellowish-brown with darkened tarsi, femora and tibiae darkened apically. Similar to Plesioaxymyia vespertina, from which it is distinguished by details of female terminalia: sternite 8 with smoothly rounded dorsoapical margin (forming somewhat protruding dorsoapical corner in P. vespertina) and completely reduced basal segment of cerci (distinct in P. vespertina). Description. Head. Head dark brown. Face sunken, clypeus convex, mouthparts brown. Palpus brown, 5 - segmented, with short (almost hidden) first segment and broadened third segment. Compound eye densely covered with short ommatrichia; divided by fine groove into upper and lower hemispheres of unequal size and with deep triangular excision opposite antennal base (Fig. 2 B). Three ocelli arranged in equilateral triangle, placed on elevated tubercle. Frons with a few brownish hairs above antennal bases and between ocellar triangle and compound eye. Posterior part of head with numerous brownish hairs. Antenna 16 - segmented, brown; pedicel yellowish apically; middle flagellomeres about twice as wide as long. Thorax. Mesonotum dark brown, thinly dusted, lacking any larger setae but covered with tiny yellowish hairs; a pair of narrow transverse shiny patches present along prescutal suture (Fig. 2 B); prescutum yellowish laterally. Scutellum yellowish-brown, strongly convex, with short hairs along posterior margin. Pleura brown. Wing. Wing length 4.08 mm. Wing hyaline with light brownish tinge (Fig. 2 C); brown elongated pterostigma occupies apical half of R 1. Costa hardly produced beyond R 4 + 5. Sc curved into costa proximally to Rs; Sc-r reduced. Rs with kink; R 2 + 3 forked well beyond apex of R 1, R 2 deviates in slightly obtuse angle. Crossvein r-m perpendicular to R 4 + 5. M 1 + 2 branching slightly before apex of R 1; section of M-stem distal to r-m about as long as M 1, longer than M 2 and about twice as long as its section proximal to r-m. M 4 straight; CuA distinctly sinuous. CuP short, scarcely reaching beyond posteromedial angle of wing. Anal lobe well-developed. Macrotrichia on wing veins not visible. Halter brown. Legs. Coxa, trochanters, femora and tibiae yellowish-brown; all femora and tibiae darkened apically; tarsi brownish. Hind tibia slightly curved in middle, with brush of bristly hairs posteroapically. Ratio of basitarsus to tibia: bt 1: t 1 – 0.45, bt 2: t 2 – 0.43, bt 3: t 3 – 0.30. Tibial spurs not developed. Abdomen. Abdomen brown. Tergites 1–7 with sparse hairs posteriorly. Terminalia (Fig. 3) brown. Tergite 8 approximately one-third length of sternite 8, rounded and setose apically; sternite 8 lengthened, tapered apically, with sparse short hairs. Cercus one-segmented; basal segment not developed; apical segment about 4 times longer than wide, bearing ca. 10 setae. Etymology. The species epithet is from the Latin imprevistus (unexpected, unforeseen), stressing that the finding of this species in Northwest Russia was a real surprise. Distribution. The species is currently known only from the type locality in Russian Karelia (Northwest Russia). Biology. The adult was collected with a Malaise trap set in Vaccinium myrtillus type pine- and spruce-dominated forest. The larval biology is unknown.