Pseudexechia parallela ( Edwards, 1925 )

Kjaerandsen, Jostein, 2009, The genus Pseudexechia Tuomikoski re-characterized, with a review of European species (Diptera: Mycetophilidae), Zootaxa 2056, pp. 1-45 : 31-32

Pseudexechia parallela ( Edwards, 1925)

(Figs 3D, 12A–D)

Exechia parallela Edwards, 1925:596 , fig. 64

Exechia parallela Stackelberg, 1948:102 , figs 16–17

Exechia parallela Stackelberg, 1969:298 [452 in English translation], figs 185,1 a&b nec Pseudexechia parallela ; Krivosheina et al. 1986:155, figs 45,1 & 45,5 Pseudexechia parallela ; Kjaerandsen & Chandler 2006:42, figs 1 A–D = Pseudexechia hamulata ( Lackschewitz, 1937) ; Kjaerandsen & Chandler 2006: 42

Diagnostic characters: P. parallela forms together with P. monica a group of small Pseudexechia species with dark brown mesoscutum with fused thoracic stripes, and with reduced size of the gonostylus relative to the gonocoxite. It can be separated from P. monica by unique characters in the male terminalia, including the ventral branch of gonostylus that is apicodorsally pointed, the hypandrial lobe being concave with a small, slightly diverging split apically, and the hypoproct forming a long, only slightly down-curved cylindrical process. The female can be distinguished by coloration, size and having two-segmented cercus.

Description. Male (n = 6, except where otherwise stated). Total length 3.7–4.8, 4.3 mm. Wing length 2.56–3.2, 2.82 mm, or 2.98–3.23, 3.14 x as long as profemur. Antenna 1.34–1.66, 1.51 mm long.

Coloration (pinned specimen). Moderately bi-coloured in brown and yellow; mesonotal stripes indistinct, diffusely defined, dark; humeral area less pale. Wings unmarked, yellowish tinted. Legs all pale. Abdomen dark with broad triangular, apical band on tergite I–V, tergite VI all dark; terminalia yellow.

Head. Width / length to frontal tubercle 1.4–1.48, 1.44. First flagellomere 1.67–2.04, 1.85 times as long as second flagellomere. Second flagellomere 1.29–1.94, 1.66 times as long as wide. Median ocellus vestigial or absent, lateral ocellus touching compound eye. Length / width of clypeus 1.1–1.28, 1.18. Antepenultimate segment 0.1–0.11, 0.1 mm long, palpomere ratios 1: 1.11–1.44, 1.3: 1.83–2.62, 2.42.

Thorax. Mesonotum length 0.82–0.98, 0.9 mm, or 0.31–0.34, 0.32 x as long as wing. Proepisternum with 2 strong bristles.

Wings (Fig. 3D). Wing length to length of R1 2.24–2.4, 2.32; wing length to length of R5 1.73–1.77, 1.75. Length of r-m to length of M-petiole 0.89–1.11, 1. R4+5-bending index 1.14–1.28, 1.21. Fork length ratio 0.76–0.8, 0.78. Fork width ratio 0.8–1.2, 0.98. M-ratios 0.58–0.63, 0.6 and 0.64–0.7, 0.66. CuA-ratios 1.35–1.53, 1.45 and 1.81–2.11, 1.99. CuP length to length of wing 0.41–0.49, 0.45. A1 length to length of wing 0.34–0.38, 0.36.

Legs. Leg ratios given for fore, mid and hind leg: LR 1.11–1.17, 1.14: 0.81–0.86, 0.84: 0.63–0.68, 0.65; SV 1.61–1.69, 1.65: 2.04–2.15, 2.08: 2.52–2.68, 2.61; BV 1.51–1.65, 1.57: 1.87–2.05, 1.94 (n=5): 2.76–3.1, 2.98; TR 1.53–1.67, 1.58: 1.58–1.74, 1.67: 1.85–2.07, 1.96.

Terminalia ( Figs 12 A–C). Gonocoxite less deeply excavated, with indistinct condyles; sternal sclerite forming small, subsquare plate. Hypandrial lobe conic, triangular. Aedeagal guides present, elongated. Gonostylus small, retracted; dorsal branch truncated, with club-shaped, whitish tip; dorsointernal branch forming large, subsymmetric, broad lamellate fan; medial branch present as small knob with three setae; ventral branch forming medium sized spatula with acute angled apicodorsal corner, ventrolaterad with 2–4 fan-tipped setae; internal branch forming large, striated cushion; anterior branch ventrally directed, subrectangular cushion. Tergite IX wide subrectangular, divided mesally. Pseudocercus medium sized, setose. Cercus forming small knob, 1.56–2, 1.75 as long as wide in dorsal view. Hypoproct long, acuminate, straight. Epiproct vestigial or absent.

1.56–2, 1.75

Female (n = 1). Total length 4.4 mm. Wing length 2.84 mm, or 3.23 x as long as profemur. Antenna 1.4 mm long.

Coloration. As in male except more extensively yellow markings on abdomen.

Head. Width / length to frontal tubercle 1.45. First flagellomere 1.67 times as long as second flagellomere. Second flagellomere 1.67 times as long as wide. Median ocellus vestigial or absent, lateral ocellus touching compound eye. Length / width of clypeus 1.14. Antepenultimate segment 0.12 mm long, palpomere ratios 1: 1.18: 2.1.

Thorax. Mesonotum length 0.96 mm, or 0.34 x as long as wing. Proepisternum with 2 strong bristles.

Wings. Wing length to length of R1 2.29; wing length to length of R5 1.67. Length of r-m to length of Mpetiole 1.11. R4+5-bending index 1.28. Fork length ratio 0.74. Fork width ratio 1. M-ratios 0.58 and 0.63. CuAratios 1.56 and 2.19. CuP length to length of wing 0.48. A1 length to length of wing 0.35.

Legs. Leg ratios given for fore, mid and hind leg: LR 1.14: 0.87: 0.67; SV 1.64: 2.03: 2.56; BV 1.56: 1.99: 2.96; TR 1.61: 1.79: 2.03.

Terminalia ( Fig 12 D). Tergite VII widely excavated dorsally, forming smooth, rounded posterior edge; apicolateral corner with nude area; setae along margin short, slender. Tergite VIII wide, subrectangular. Tergite IX fused with postgenital plate. Cercus two-segmented, apical segment ovate, the two combined 3.12 as long as wide in lateral view. Postgenital plate (gonapophysis IX) elongated, with obtuse tip. Sternite VII slightly shorter than tergite VII. Sternite VIII acute. Gonapophysis VIII weak, broad.

Distribution. Holarctic, widely distributed in Europe.

Biology unknown.

Type material examined: Holotype female of P. parallela : ENGLAND ( U. K.): Newmarket, Cambs [52°14'43''N, 0°24'12''E], 23 Sep 1888 [ BMNH, Leg. G. H. Verrall, pinned with terminalia in balsam preparation mounted on pin, JKJ – SPM –005283]. Holotype male of P. hamulata : LATVIA: Paplacken, Kurl [56°52N, 024°36E], 7 Oct 1934 [ ZMHB, Leg. P. Lackschewitz, pinned with terminalia in balsam preparation mounted on pin, JKJ – SPM – 011949].

Other material examined: ENGLAND ( U. K.) (Coll. Chandler unless otherwise stated, all NCC Wetland Survey. Leg. A. Foster and D. Procter): Cambridgeshire, Chippenham Fen, 10–24 Aug 1988 2 males (Coll. Chandler); Norfolk, 13 Jun–11 Jul 1988 — 5 males, 2 females ( MZLU, 1 male & 1 female on slide); Reedham, 27 Jun–11 Jul 1988 — 1 male, 11 Jul–12 Aug 1988 — 1 male, 12 Aug–20 Sep 1988 — 2 males ( MZLU, 1 male on slide), 26 Aug 1988 — 3 males; Brancaster, 1–15 Jul 1988 — 9 males ( MZLU, 1 male, pinned); Stallode Wash, 29 Jun–8 Jul 1988 — 1 male; Catfield, 29 Sep–12 Oct 1988 — 1 male, 12 Oct 1988 — 1 male; Middle Harling, 26 Jun–17 Jul 1988 — 1 male; Wendling, 14–24 Sep 1988 — 1 male; Old Buckenham Fen, 28 Jun–12 Jul 1988 — 1 male; Thompson Common, 1988 — 1 male; Suffolk, Walberswick, 14–29 Aug 1988 — 4 males; WAL ES (all Coll. Chandler, NCC Peatland Survey, Leg. Holmes, Boyce & Reed): Anglesey, Cors Erddreiniog, 27 Jul 1988 — 2 males; Cors Bodeilio, Molinia / Myrica bog and Phragmites bed, 28 Jun 1988 — 1 female, 26 Jul 1988 — 1 female, 5 Oct 1988 — 1 male; Rhos-y-Gad, calcareous flush fen, 27 Jul 1988 — 1 male, 1 female; West Glamorgan, Fairwood Common, Juncus flush, 4 Oct 1989 — 1 female; Pant-y-Sais, among Carex acutiformis and in Molinia bog, 5 Oct 1989 — 2 males, 1 female; SWEDEN: SK, Häckeberga NR, 55°35'40.72"N, 13°25'14.56"E, 29 Sep 1988 ( MZLU, Leg. L. Huggert) — 3 males (2 on slides); ESTONIA: Tôrva, Helme Cave [old refuge cave in sandstone, about 50 m deep], 58°01'00"N, 025°53'00"E, 19 Jan 1996 ( MZLU, Leg. O. Kurina) — 2 males (on slides); RUSSIA: Kamtschatka, Bolscherjetsk, 52°53'34"N, 157°02'30"E, 1 Jul 1917 (Leg. Y. Wuorentaus) — 1 male ( MZLU, pinned with cleared terminalia in glycerine); USA: Minnesota, Cook co., Hovland N. J., Min. F. S., 47°50'20"N, 089°58'19"W, 14 Jul 1968 ( USNM, Leg. E. F. Cook) — 1 male (on slide).

Figures

FIGURE 12. Pseudexechia parallela (Edwards, 1925). — A. Male terminalia, ventral view. — B. Male gonostylus, internal view, enlarged. — C. Male tergite IX and cerci, dorsal view. — D. Female terminalia, lateral view.