Stenochironomus paraokialbus Song & Qi, 2025

Stenochironomus paraokialbus Song & Qi sp. nov. ( Figs. 2–3 View FIGURE 2 View FIGURE 3 , GenBank accession: PV842226– PV842230)

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Diagnostic characters. The male imago can be distinguished from known species in this genus by the following combination of characters: Wing with two rather faint dark areas, one around r-m and FCu, the other in the apical portion. superior volsella short and small, a palmate structure bearing four finger-like branches each bearing a single long seta; inferior volsella elongate, with three long setae and a slender terminal spine, posterior margin of tergite IX with 8–10 setae and eight spines.

Description.

Male (n = 6).

Total length 3.71–5.09, 4.41 mm. Wing length 1.93–2.73, 2.25 mm. Total length/wing length 1.86–2.17, 1.95. Wing length/length of profemur 1.6–1.93, 1.77.

Coloration of the preserved specimen ( Fig. 2 View FIGURE 2 ). Head yellow, antenna brown; thorax pale yellow, postnotum and scutum with brown spots ( Fig. 3A View FIGURE 3 ); abdominal tergites I–III pale yellow, tergites IV–VIII and hypopygium brown ( Fig. 3B View FIGURE 3 ); leg segments largely pale yellow, but all femora with a narrow apical brown ring, all fourth tarsomeres (ta 4) with a brown ring on apical 1/2, fifth tarsomeres (ta 5) entirely brown; front tibia brown, first tarsomere (ta 1) with basal half brown and an apical brown, second and third tarsomeres (ta 2-3) each with an apical brown; hind tibia brown on basal half and apex, other leg portions pale yellow ( Fig. 3C View FIGURE 3 ).

Head. AR 0.55–0.67, 0.59. Temporal setae 10–14, 11. Clypeus with 16–25, 19. setae. Tentorium 165–226, 201 μm long, 34–53, 44 μm wide. Palpomere lengths (in μm): 34–46, 41; 43–58, 51; 196–240, 210; 98–154, 125; 127–244, 193. L: 5 th /3 rd: 0.65–1.05, 0.92.

Wing. Wing with two rather faint dark areas, one around r-m and FCu, the other in the apical portion ( Fig. 3D View FIGURE 3 ). VR 1.02–1.07, 1.03. R with 27–41, 32 setae, R 1 with 26–42, 33 setae, and R 4+5 with 45–59, 49 setae. Squama with 12–13, 12 setae.

Thorax. Dorsocentrals 13–32, 22. acrostichals 7–19, 14. prealars 5–9, 6. Scutellum with 6–12, 9 setae.

Legs. Scale of front tibia 34–61, 46 μm long, with 3 strong setae. Mid tibiae with fused combs, 52–66, 59. μm long. hind tibiae with fused combs, 73–97, 89 μm long. Spurs on mid tibiae 30–41, 34 μm and 38–49, 44 μm long; spurs on hind tibia 21–39, 30 μm and 32–40, 34 μm long. Width at apex of front tibia 62–70, 68 μm, of mid tibia 70–81, 74 μm, of hind tibia 71–88, 80 μm. Lengths (in μm) and proportions for legs in Table 2.

Hypopygium ( Fig. 3E View FIGURE 3 ). Anal point 105–147, 127 μm long, 58–78, 64 µm wide at base, 8–12, 9 µm wide at apex, apex of anal point rounded. Tergite IX with 14–23, 16 long setae medially, posterior margin of tergite IX with 8–10 setae and 8 spines. Phallapodeme 90–114, 105 μm long; transverse sternapodeme 23–35, 29 μm long. Gonocoxite 166–188, 168 μm long. Superior volsella short and small, a palmate structure bearing four finger-like branches each bearing a single long seta, 17–40, 32 μm long, 14–33, 21 μm wide, with 4 long setae ( Fig. 3F View FIGURE 3 ). Inferior volsella elongate, 187–255, 223 μm long, with 3 long setae and a slender terminal spine. Gonostylus slender, inner margin concave, and with 3 long setae on inner margin of apical portion, 214–254, 227 μm long, with 8–13, 10 setae along inner margin in distal 1/2. HR 0.69–0.79, 0.74, HV 1.73–2.2, 1.93.

Type material. Holotype. ♂ (TZU: WZWC338 ), China, Zhejiang Province, Wenzhou City, Wencheng county , 27.6489°N, 120.0514°E, 9-V-2023, light trap, leg. C. SONG GoogleMaps . Paratypes. 3♂♂, same data as holotypes GoogleMaps ; 2♂♂, China, Fujian province, Wuyi mountain national park, 27.6020°N, 117.7890°E, 17-IV-2021 light trap, leg. KH. ZHONG GoogleMaps .

Etymology. From the Latin, ‘ para ’ meaning similar, referring to the new species resemblance to S. okialbus Sasa, 1990 .

Remarks. Morphologically, S. paraokialbus shows similarities to S. okialbus Sasa, 1990 and S. gibbus (Fabricius, 1805) based on the following characters: Wing with two rather faint dark areas, one around r-m and FCu, the other in the apical portion; inferior volsella elongate; the superior volsella short and small, a palmate structure bearing four finger-like branches, each bearing a single long seta. The three aforementioned species can be separated by the AR, pattern of the legs’ rings, thorax, and the abdominal tergites coloration ( Table 3). S. okialbus Sasa has an AR of 1.23–1.6, while S. paraokialbus has a significantly lower AR of 0.55–0.67 0.59.

In terms of leg coloration, the tibiae and tarsomeres of S. okialbus Sasa lack distinct coloration, S. gibbus (Fabricius, 1805) exhibits more extensive leg pigmentation with the front femur having a brown spot on its apical half, the mid and hind femur being pigmented over their apical 0.47 to the entire length, the fore and mid tibiae bearing slight pigmentation on their basal 0–0.34, the hind tibia being pigmented on its basal 0.60 to the entire length, and all ta 5 are brown. In S. paraokialbus all femurs bear a brown ring apically; the fourth tarsomeres (ta 4) each display a brown ring occupying the apical half of the segment, while the fifth tarsomeres (ta 5) are uniformly brown. Specifically, the front tibia is uniformly brown, and its first tarsomere (ta 1) has a brown basal half and an apical brown, the second and third tarsomeres (ta 2-3) each with an apical brown; hind tibia brown on basal half and apex, with the remaining leg portions retaining the pale-yellow coloration. Furthermore, compared with the other two species, S. gibbus (Fabricius, 1805) median vitta and pleural region are without dark pigmentation. The abdominal tergites IV–VI of S. okialbus Sasa and S. gibbus (Fabricius, 1805) are uniformly pale yellow, contrasting with the brown coloration of the same tergites in S. paraokialbus .