Pseudexechia pectinacea ( Ostroverkhova, 1979 )

Kjaerandsen, Jostein, 2009, The genus Pseudexechia Tuomikoski re-characterized, with a review of European species (Diptera: Mycetophilidae), Zootaxa 2056, pp. 1-45 : 16-17

Pseudexechia pectinacea ( Ostroverkhova, 1979)

( Figs 4 E, 5B, 7A–D)

Rymosia pectinacea Ostroverkhova, 1979:178 , fig. 34,5

Pseudexechia parallela ; Krivosheina et al. 1986:155, figs 45,1 & 45,5 Pseudexechia trisignata ; Zaitzev 1999:188, figs 108,9 & 109,1 Pseudexechia trisignata ; Zaitzev 2003:193, figs 42,2 & 42,6

Diagnostic characters. Rather similar to P. trisignata and P. tuomikoskii , but can be distinguished by its distinctly bi-coloured pattern in dark greyish brown and yellow with a broad pale band along margin of mesonotum. Distinctive features of the male terminalia include a rectangular hypandrial lobe with sharp apices and corners; the ventral branch of gonostylus forming a small, round, symmetrical spatula; and the smooth whitish tip of dorsal branch of gonostylus being slightly acute. Females are distinguished by the combination of coloration; having tergite VII straight dorsally, forming a smooth, straight posterior margin with long, slender seta; and by having obtuse tip of sternite VIII.

Description. Male (n = 6, except where otherwise stated). Total length 4.5–6, 5.3 (n=10) mm. Wing length 3.2–4.04, 3.71 mm, or 3.19–3.42, 3.31 x as long as profemur. Antenna 1.58–1.8, 1.71 mm long.

Coloration (specimen in alcohol). Distinctly bi-coloured in dark greyish brown and yellow; mesonotal stripes indistinct, diffusely defined and dark; pale humeral area extended to form broad pale band along entire margin of mesonotum. Wings unmarked, yellowish tinted. Legs all pale. Abdomen dark with small triangular, apical band on tergite II–V, tergite VI all dark; terminalia pale yellow.

Head ( Fig. 4 E). Width / length to frontal tubercle 1.49–1.65, 1.57. First flagellomere 1.67–1.88, 1.77 times as long as second flagellomere. Second flagellomere 1.76–1.94, 1.84 times as long as wide. Median ocellus small but distinct, lateral ocellus touching compound eye. Length / width of clypeus 1.25–1.44, 1.34. Antepenultimate segment 0.11–0.14, 0.13 mm long, palpomere ratios 1: 1.4–1.66, 1.47: 2.49–2.83, 2.61.

Thorax. Mesonotum length 0.9–1.14, 1.07 mm, or 0.28–0.32, 0.29 x as long as wing. Proepisternum with 1 strong bristle.

Wings. Wing length to length of R1 2.2–2.36, 2.28; wing length to length of R5 1.7–1.76, 1.73. Length of r-m to length of M-petiole 1–1.25, 1.11. R4+5-bending index 1.44–1.84, 1.64. Fork length ratio 0.9–0.94, 0.91. Fork width ratio 0.83–1.19, 0.96. M-ratios 0.62–0.68, 0.65 and 0.69–0.77, 0.74. CuA-ratios 1.13–1.28, 1.19 and 1.6–1.74, 1.67. CuP length to length of wing 0.45–0.49, 0.47. A1 length to length of wing 0.34–0.36, 0.34.

Legs. Leg ratios given for fore, mid and hind leg: LR 1.06–1.14, 1.1: 0.82–0.91, 0.88: 0.7–0.74, 0.72; SV 1.67–1.74, 1.71: 1.99–2.18, 2.04: 2.34–2.49, 2.4; BV 1.55–1.68, 1.59: 2.05–2.17, 2.11 (n=5): 3.2–3.51, 3.39; TR 1.48–1.78, 1.56: 1.75–1.94, 1.83: 2.27–2.52, 2.36.

Terminalia ( Figs 7 A–C). Gonocoxite subsquare, with distinct condyles; sternal sclerite forming small, sclerotized, bifurcated plate. Hypandrial lobe subrectangular, with sharp apices and corners. Aedeagal guides subrectangular. Gonostylus medium sized; dorsal branch elongated, with slightly acute, whitish tip; dorsointernal branch forming large, asymmetric, broad lamellate fan; medial branch present as large knob with three setae; ventral branch forming small, round, symmetrical spatula, ventrolaterad with 2–4 fan-tipped setae; internal branch forming large, striated cushion; anterior forming branch ventrally directed, subrectangular cushion. Tergite IX wide subrectangular, fused, with strong mesal suture. Pseudocercus long, setose. Cercus forming small knob, 1.21–1.82, 1.56 (n=5) as long as wide in dorsal view. Hypoproct triangular, apiculate. Epiproct vestigial or absent.

Female (n = 4, except where otherwise stated). Total length 5–6.2, 5.6 (n=7) mm. Wing length 3.96–4.3 mm, or 3.29–3.41 x as long as profemur. Antenna 1.42–1.82 mm long.

Coloration. As in male except tergite VI and VII usually also with pale apical bands.

Head. Width / length to frontal tubercle 1.23–1.55. First flagellomere 1.47–1.88 times as long as second flagellomere. Second flagellomere 1.68–2.15 times as long as wide. Median ocellus small but distinct, lateral ocellus touching compound eye. Length / width of clypeus 1.25–1.4. Antepenultimate segment 0.14–0.16 mm long, palpomere ratios 1: 1.31–1.44: 2.22–2.42.

Thorax. Mesonotum length 1.12–1.3 mm, or 0.28–0.31 x as long as wing. Proepisternum with 1 strong bristle.

Wings. Wing length to length of R1 2.14–2.29; wing length to length of R5 1.66–1.73. Length of r-m to length of M-petiole 0.87–1.33. R4+5-bending index 1.64–1.75. Fork length ratio 0.83–0.96. Fork width ratios 0.87–1. M-ratios 0.57–0.66 and 0.66–0.78. CuA-ratios 1.04–1.21 and 1.42–1.67. CuP length to length of wing 0.45–0.47. A1 length to length of wing 0.33–0.35.

Legs. Leg ratios given for fore, mid and hind leg: LR 1.09–1.14: 0.87–0.91: 0.73–0.76; SV 1.63–1.72: 1.95–2.04: 2.29–2.4; BV 1.61–1.69: 2.22–2.38: 3.41–3.55; TR 1.5–1.62: 1.85–1.95: 2.34–2.57.

Terminalia ( Fig. 7 D). Tergite VII straight dorsally, with smooth posterior edge; apicolateral corner with nude area; setae along margin long, slender. Tergite VIII wide, subrectangular. Tergite IX fused with postgenital plate. Cercus one-segmented, long sinusoid with obtuse tip, 3.52–3.88 as long as wide in lateral view. Postgenital plate (gonapophysis IX) elongated, with round, obtuse tip. Sternite VII subequal in length to tergite VII. Apex of sternite VIII obtuse. Gonapophysis VIII weak, narrow.

Distribution. The Japanese record indicates a Wide Palaearctic distribution. In Western Europe so far reported only from Finland and Sweden.

Biology unknown.

Material examined. FINLAND: Ks, Kuusamo, Kiutaköngäs, 19–24 Jul 1967 ( MZH, Leg. R. Tuomikoski) — 1 male; SWEDEN: LU, Jokkmokk, Porsitjärn/Porsi VVO, 1.5 km SE Vuollerim, 66°25'28''N, 20°40'17''E, 60 m a.s.l., 13 Aug–13 Oct 2004 ( MZLU, Leg. M. Karström) — 1 female, 10 males; 1–15 May 2005 ( MZLU, Leg. K. Hedmark & M. Karström) — 1 female, 1 male; 15 May–1 Jun 2005 ( MZLU, Leg. K. Hedmark & M. Karström) — 5 females; 1–15 Jun 2005 ( MZLU, Leg. K. Hedmark & M. Karström) — 1 male; 16 Sep–1 Oct 2005 ( MZLU, Leg. K. Hedmark & M. Karström) — 1 female, 5 males; 1–16 Oct 2005 ( MZLU, Leg. K. Hedmark & M. Karström) — 1 female, 1 male; Jokkmokk, Bombmurkleskogen VVO, 4 km SSE Messaure, 66°38'47'' N 20°22'49''E, 85 m a.s.l., 10 Jun 2006 ( MZLU, Leg. J. Kjaerandsen) — 1 male; 66°38'59''N, 20°22'45''E, 17 Jun 2004 ( MZLU, Leg. J. Kjaerandsen) — 1 male; Jokkmokk, Vuollerim, Varjek, Varjekbäcken/Jovvamyran, 66°23'48''N, 20°26'58''E, 16 Sep 2000 (Coll. & Leg. K. Hedmark) — 1 male; JAPAN: Hokkaido, Kamikawa-cho, O-bako, Souunkyo, 43°42'10''N, 143°0'43''E, 713 m. a.s.l., 5 Oct 2006 ( MZLU, Leg. J. Kjaerandsen) — 2 males.

Figures

FIGURE 4. Morphology of Pseudexechia [A – D + F – J = P. trisignata (Edwards, 1913), E = P. pectinacea (Ostroverkhova, 1979)]. — A. Head in dorsal view. — B. Antenna, dorsal view. — C. Antenna, lateral view — D. Segment III – V of maxillary palp. — E. Face enlarged. — F. Thorax, lateral view. — G. Fore tarsus V. — H. Mid tarsus V. — I. Hind tarsus V. — J. Apex of hind tibia, medial view. Abbreviations: anepist = anepisternum; clyp = clypeus; cx 1 = forecoxa; cx 2 = midcoxa; cx 3 = hindcoxa; emp = empodium; fc = face; flag I = first flagellar segment; flag II = second flagellar segment; fr fur = frontal furrow; fr tub = frontal tubercle; htl = halter; ltg = laterotergite; m oc = medial ocellus; mtg = mediotergite; proepist seta = proepisternal seta; sc = scutum; sctl = scutellum; sens pit = sensory pit; t comb = tibial comb.

FIGURE 7. Pseudexechia pectinacea (Ostroverkhova, 1979). — A. Male terminalia, ventral view. — B. Male gonostylus, internal view, enlarged. — C. Male tergite IX and cerci, dorsal view. — D. Female terminalia, lateral view.