Pseudexechia trisignata ( Edwards, 1913 )

Kjaerandsen, Jostein, 2009, The genus Pseudexechia Tuomikoski re-characterized, with a review of European species (Diptera: Mycetophilidae), Zootaxa 2056, pp. 1-45 : 14-15

Pseudexechia trisignata ( Edwards, 1913)

( Figs 2 A, 3A, 4A–D&F–J, 5A, 6A–D)

Exechia trisignata Edwards, 1913:370 , figs 73–75

? Exechia trisignata Stackelberg, 1969:300 [454 in English translation], figs 185,4 a&b nec Pseudexechia trisignata ; Zaitzev 1999:188, figs 108,9 & 109,1

nec Pseudexechia trisignata ; Zaitzev 2003:193, figs 42,2 & 42,6

nec Pseudexechia trisignata ; Sasakawa & Ishizaki 1999:156, figs 23–25

Diagnostic characters. Rather similar to P. pectinacea and P. t u o m i k o s k i i, but can be distinguished by its overall dull brown coloration (with a distinct greyish dusting on dry specimens), and narrow pale bands on abdominal segments. Distinctive features of the male terminalia include a rather rounded hypandrial lobe with smoothly rounded corners; the ventral branch of gonostylus having an angular corner basodorsally, making the spatula broadest basally; and the smooth whitish tip of dorsal branch of gonostylus being evenly thick. Females are distinguished by the combination of coloration; having tergite VII widely but shallowly excavated posterodorsal, forming a rounded, weakly crenulated posterior margin with long, slender seta; and by having a truncated tip of sternite VIII.

Description. Male (n = 5, except where otherwise stated). Total length 5.5–6.1, 5.8 (n=10) mm. Wing length 4.1–4.18, 4.14 mm, or 3.2–3.49, 3.36 x as long as profemur. Antenna 1.86–2.1, 2.03 mm long.

Coloration (specimen in alcohol). A dull brown species with a distinct greyish dusting; mesonotal stripes fused, hardly discernable, dark; humeral area dark, sometimes with small pale corner. Wings yellowish, with indistinct spot at base of posterior fork and greyish smoked towards tip. Legs pale with dark spots on coxae and femur. Abdomen dark with narrow to slightly triangular pale bands on tergite II–V, tergite VI extra dark; terminalia dark yellow.

Head ( Figs 4 A–D). Width / length to frontal tubercle 1.32–1.54, 1.43. First flagellomere 1.38–1.63, 1.52 times as long as second flagellomere. Second flagellomere 2–2.56, 2.28 times as long as wide. Median ocellus small but distinct, lateral ocellus touching compound eye. Length / width of clypeus 1.29–1.53, 1.39. Antepenultimate segment 0.14–0.15, 0.15 mm long, palpomere ratios 1: 1.29–1.52, 1.39: 2.24–2.52, 2.34.

Thorax. Mesonotum length 1.14–1.22, 1.18 mm, or 0.28–0.29, 0.29 x as long as wing. Proepisternum with 1 (–2) strong bristles.

Wings (Fig. 3A). Wing length to length of R1 2.13–2.24, 2.18; wing length to length of R5 1.67–1.69, 1.68. Length of r-m to length of M-petiole 1–1.31, 1.12. R4+5-bending index 1.6–1.8, 1.68. Fork length ratio 0.77–0.91, 0.85. Fork width ratio 0.76–0.96, 0.84. M-ratios 0.53–0.65, 0.61 and 0.6–0.73, 0.68. CuA-ratios 1.1–1.26, 1.21 and 1.6–1.76, 1.7. CuP length to length of wing 0.43–0.49, 0.46. A1 length to length of wing 0.33–0.35, 0.34.

Legs. Leg ratios given for fore, mid and hind leg: LR 1.06–1.14, 1.1: 0.81–0.88, 0.86: 0.69–0.72, 0.71; SV 1.62–1.75, 1.69: 1.96–2.16, 2.05: 2.39–2.47, 2.42; BV 1.62–1.7, 1.65: 2.11–2.22, 2.16: 3.24–3.47, 3.35; TR 1.46–1.51, 1.49: 1.69–1.78, 1.73: 2.12–2.25, 2.19.

Terminalia ( Figs 6 A–C). Gonocoxite subsquare, with distinct condyles; sternal sclerite forming small, sclerotized, bifurcated plate. Hypandrial lobe subrectangular, with softly rounded apicolateral corner. Aedeagal guides subrectangular, apically pointed. Gonostylus medium sized; dorsal branch elongated, with obtuse, whitish tip; dorsointernal branch forming large, asymmetric, broad lamellate fan; medial branch present as large knob with three setae; ventral branch forming medium sized, strongly asymmetrical spatula, with angular basodorsal corner making the spatula broadest basally, ventrolaterad with 2–4 fan-tipped setae; internal branch forming large, striated cushion; anterior branch forming ventrally directed, subrectangular cushion. Tergite IX wide subrectangular, fused, with strong mesal suture. Pseudocercus long, setose. Cercus forming small knob, 1.44–1.69, 1.59 as long as wide in dorsal view. Hypoproct triangular, apiculate. Epiproct vestigial or absent.

Female (n = 5, except where otherwise stated). Total length 5–6.4, 5.6 (n=10) mm. Wing length 4.04–4.64, 4.4 mm, or 3.38–3.6, 3.49 x as long as profemur. Antenna 1.74–1.86, 1.8 mm long.

Coloration. As in male except indistinct pale bands on abdomen and tergite VI not extra dark.

Head. Width / length to frontal tubercle 1.48–1.64, 1.55. First flagellomere 1.38–1.75, 1.63 times as long as second flagellomere. Second flagellomere 2.26–2.67, 2.42 times as long as wide. Median ocellus small but distinct, lateral ocellus touching compound eye. Length / width of clypeus 1.19–1.4, 1.29. Antepenultimate segment 0.15–0.16, 0.15 mm long, palpomere ratios 1: 1.25–1.53, 1.39: 2.12–2.4, 2.24.

Thorax. Mesonotum length 1.12–1.34, 1.22 mm, or 0.26–0.29, 0.28 x as long as wing. Proepisternum with 1 strong bristle.

Wings. Wing length to length of R1 2.06–2.34, 2.19; wing length to length of R5 1.65–1.86, 1.71. Length of r-m to length of M-petiole 1.07–1.42, 1.19. R4+5-bending index 1.55–1.94, 1.74. Fork length ratio 0.88–0.9, 0.89. Fork width ratio 0.72–0.96, 0.85. M-ratios 0.58–0.64, 0.6 and 0.65–0.72, 0.68. CuA-ratios 1.05–1.22, 1.14 and 1.47–1.69, 1.57. CuP length to length of wing 0.42–0.46, 0.43. A1 length to length of wing 0.3–0.38, 0.33.

Legs. Leg ratios given for fore, mid and hind leg: LR 1.07–1.12, 1.09: 0.86–0.89, 0.87: 0.7–0.73, 0.72; SV 1.66–1.74, 1.71: 1.99–2.05, 2.01: 2.36–2.44, 2.39; BV 1.7–1.78, 1.74: 2.27–2.35, 2.31: 3.29–3.48, 3.39; TR 1.48–1.58, 1.52: 1.77–1.89, 1.82: 2.2–2.37, 2.26.

Terminalia ( Fig. 6 D). Tergite VII widely but shallowly excavated dorsally, forming rounded, weakly crenulated posterior margin; 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, 2.5–2.79, 2.63 as long as wide in lateral view. Postgenital plate (gonapophysis IX) elongated, with apiculate tip. Sternite VII subequal in length to tergite VII. Apex of sternite VIII truncated. Gonapophysis VIII weak, narrow.

Distribution. Palaearctic, in Europe mainly western. The reported Eastern European ( Krivosheina et al. 1986) and Eastern Palaearctic ( Zaitzev 1999, 2003) distribution is questionable due to mixing with P. pectinacea .

Biology. The records reared from soft gill fungi like Naucoria sp. and Galerina sp. ( Chandler 1993) is yet to be confirmed due to possible mixing with P. tuomikoskii and P. pectinacea .

Type material examined: Holotype male, UK, SCOTLAND: Beattock, 55°18'15''N, 3°27'9''W, undated (Marked BMNH (E) #236695, Leg. C. G. Lamb) [ BMNH, JKJ – SPM –005284].

Other material examined: NORWAY: HOI, Kvinnherad, Varaldsøy, in fissures close to a cave opening, 60°6'6''N, 6°1'17''E, 10 Mar 1991 ( MZLU, Leg. J. Kjaerandsen) — 11 females, 5 males; Kvinnherad, Fugleberg, in man-made soapstone caves, 60°0'41''N, 5°51'24''E, 9 Mar 1991 ( MZLU, Leg. J. Kjaerandsen) — 1 female; HOY, Bergen, Haukeland, in mine galleries, 12 Jan 1991 ( MZLU, Leg. J. Kjaerandsen) — 3 females, 1 male; Sveio, Førde, Solheimshaugen, 27 Mar 1991 ( MZLU, Leg. J. Kjaerandsen) — 1 female; Sveio, Førde, 10 Nov 1990 ( MZLU, Leg. J. Kjaerandsen) — 1 male; 1 Apr 1991 ( MZLU, Leg. J. Kjaerandsen) — 6 females, 3 males; 12 Jan 1992 ( MZLU, Leg. J. Kjaerandsen) — 1 female; Bergen, Haukeland, in mine galleries, 60°21'16''N, 5°27'19''E, 21 Mar 1991 ( MZLU, Leg. J. Kjaerandsen) — 1 female; Bergen, Riple, 60°18'51''N, 5°26'33''E, 12 Mar 1991, ( MZLU, Leg. J. Kjaerandsen) — 1 male; 23 Apr 1991 ( MZLU, Leg. J. Kjaerandsen) — 1 male; Bergen, Svartediket, 60°23'42''N, 5°22'44''E, 18 Apr 1988 ( MZLU, Leg. G. E. E. Søli) — 1 male; MRI, Sunndal, Jordalsgrenda, Jordalsøra, Hamrene, 62°46'18"N, 008°19'12"E, 140 m a.s.l. ( MZLU, Leg. J. B. Jordal), 26 Apr–13 May 2005— 1 female; 13–31 May 2005 — 1 female, 4 males; 25 Aug–15 Sep 2005 — 3 males; 15 Sep–6 Oct 2005 — 2 females, 7 males; 6–23 Oct 2005 — 16 females, 34 males; 23 Oct–11 Nov 2005 — 19 females, 24 males; 11 Nov–1 Dec 2005 — 16 females, 28 males; 1 Dec 2005 – 1 Jan 2006 — 2 females, 8 males; 1 Jan–1 Feb 2006 — 3 females, 4 males; 1 Feb–1 Mar 2006 — 1 male; 1 Mar–1 Apr 2006 — 1 male; 1–26 Apr 2006 — 5 females, 11 males; MRY, Aure, Ånes, Stølhaugen, 63°16'31"N, 008°27'30"E, 15 m a.s.l. ( MZLU, Leg. F. Oldervik), 26 Apr–13 May 2006 — 1 male; 13–31 May 2006 — 5 males; 31 May–14 Jun 2006 — 2 females, 5 males; 1 Dec 2006 – 1 Jan 2007 — 5 females, 7 males; 1 Mar–1 Apr 2007 — 1 female, 3 males; NNV, Vågan, Rørvik, 68°12'19''N, 14°14'42''E, 27 Jun 1956 ( MZLU, Leg. H. Andersson) — 1 male; STI, Oppdal, Kongsvoll, 62°17'40"N, 009°37'04"E, 1060 m a.s.l., yellow pantrap no. 15–17 at forest limit w/birch & Salix , 8–11 Jul 1992 ( MZLU, Leg. J. Skartveit) — 5 females, 1 male; SWEDEN: SK, Blentarp, Stampenbäcken, 55°35'53''N, 13°33'12''E, 28 Nov 1969 ( MZLU, Leg. B. W. Svensson) — 1 female; TO, Kiruna, Abisko, 68°21'1''N, 18°49'50''E, 20–27 Oct 1975 ( MZLU, Leg. K. Müller) — 2 males; 6–20 Oct 1975 — 1 male; Kiruna, Abisko, Stordalen, 68°21'29''N, 18°58'51''E, 18–25 Sep 1975 ( MZLU, Leg. K. Müller) — 1 male.

Figures

FIGURE 2. Habitus photos of Pseudexechia. — A. P. trisignata (Edwards, 1913) in lateral view, a dull brown species with a distinct greyish dusting, with fused thoracic stripes and narrow apical pale bands on abdomen. — B. P. aurivernica Chandler, 1978 in lateral view, a distinctly bi-coloured species in dark greyish brown and yellow, often with a reddish tinge, with distinct thoracic stripes and with large, triangular apical pale bands on abdomen — C. P. canalicula (Johannsen, 1912) in dorsal view, yet another bi-coloured species in greyish brown and yellow with distinct thoracic stripes.

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 6. Pseudexechia trisignata (Edwards, 1913). — A. Male terminalia, ventral view. — B. Male gonostylus, internal view. — C. Male tergite IX and cerci, dorsal view. — D. Female terminalia, lateral view.