Pseudexechia aurivernica Chandler, 1978

Kjaerandsen, Jostein, 2009, The genus Pseudexechia Tuomikoski re-characterized, with a review of European species (Diptera: Mycetophilidae), Zootaxa 2056, pp. 1-45 : 24-26

Pseudexechia aurivernica Chandler, 1978

( Figs 2 B, 3B, 10A–D)

Mycetophila trivittata var. b.; Zetterstedt 1852:4234

Exechia trivittata pale form; Lundström 1909:41, figs 67 & 68a Pseudexechia aurivernica Chandler, 1978:45 , figs 1,2 & 6

Pseudexechia aurivernica ; Krivosheina et al. 1986: 155, figs 45,6 & 45,7 Pseudexechia aurivernica ; Zaitzev 2003:190, figs 42,3 & 42,5

Diagnostic characters. A quite distinctively bi-coloured species, often with a reddish tinge, and broad triangular, apical band on abdominal tergites. The combination of vivid coloration and small, retracted gonostylus with boot-shaped ventral branch and conically tapered hypandrial lobe separate males of this species from other European species. Further distinctive features of the male terminalia includes having only slightly club-shaped tip of the dorsal branch of gonostylus, and dorsointernal branch forming large, subsymmetric, lamellate fan with a short stem. Females are easily distinguished by combination of coloration and having strongly dentate to laciniate posterior edge of tergite VII.

Description. Male (n = 5, except where otherwise stated). Total length 4.8–5.6, 5.1 (n=10) mm. Wing length 3.48–3.68, 3.6 mm, or 3.12–3.29, 3.19 x as long as profemur. Antenna 1.68–1.74, 1.71 mm long.

Coloration (specimen in alcohol). Distinctly bi-coloured in dark greyish brown and yellow, often with a reddish tinge; mesonotal stripes distinct, sharply defined and dark; humeral area pale. Wings unmarked, yellowish tinted. Legs all pale. Abdomen dark with broad triangular, apical band on tergite II–VI; terminalia yellow.

Head. Width / length to frontal tubercle 1.06–1.77, 1.42. First flagellomere 1.78–2.03, 1.9 times as long as second flagellomere. Second flagellomere 1.5–2.06, 1.74 times as long as wide. Median ocellus vestigial or absent, lateral ocellus touching compound eye. Length / width of clypeus 1.22–1.31, 1.25. Antepenultimate segment 0.13–0.14, 0.14 mm long, palpomere ratios 1: 1.15–1.38, 1.24: 2.15–2.79, 2.42.

Thorax. Mesonotum length 1.12–1.16, 1.14 mm, or 0.31–0.33, 0.32 x as long as wing. Proepisternum with 2 strong bristles.

Wings (Fig. 3B). Wing length to length of R1 2.25–2.36, 2.3; wing length to length of R5 1.8–1.81, 1.81. Length of r-m to length of M-petiole 1.08–1.56, 1.3. R4+5-bending index 0.86–1.07, 0.93. Fork length ratio 0.67–0.84, 0.78. Fork width ratio 0.75–0.91, 0.88. M-ratios 0.49–0.61, 0.58 and 0.54–0.67, 0.63. CuA-ratios 1.25–1.42, 1.32 and 1.69–1.91, 1.8. CuP length to length of wing 0.41–0.48, 0.45. A1 length to length of wing 0.33–0.36, 0.35.

Legs. Leg ratios given for fore, mid and hind leg: LR 1.12–1.2, 1.17: 0.86–0.94, 0.9: 0.66–0.7, 0.68; SV 1.56–1.64, 1.59: 1.91–2.05, 1.97: 2.44–2.56, 2.51; BV 1.58–1.65, 1.62: 1.98–2.1, 2.04: 2.91–3.14, 3.05; TR 1.57–1.65, 1.62: 1.72–1.8, 1.77: 1.9–2.11, 2.

Terminalia ( Figs 10 A–C). Gonocoxite subrectangular, with distinct condyles; sternal sclerite forming elongated, cordate plate. Hypandrial lobe large, conically triangular. Aedeagal guides subrectangular. Gonostylus small, retracted; dorsal branch elongated, with slightly club-shaped, whitish tip; dorsointernal branch forming large, subsymmetric, broad lamellate fan; medial branch reduced or fused with internal branch; ventral branch forming narrow, angular boot-shaped spatula, without fan-tipped setae; internal branch forming large, striated cushion; anterior branch forming ventrally directed, round cushion. Tergite IX wide subrectangular, fused, with strong mesal suture. Pseudocercus long, setose. Cercus forming small knob, 1.29–1.75 (n=4) as long as wide in dorsal view. Hypoproct long, rostrate. Epiproct vestigial or absent.

Female (n = 4, except where otherwise stated). Total length 4.5–5.6, 5 (n=10) mm. Wing length 3.46–3.86 mm, or 3.24–3.36 x as long as profemur. Antenna 1.5–1.64 mm long.

Coloration. As in male except tergite VII dark with central white spot.

Head. Width / length to frontal tubercle 1.29–1.46. First flagellomere 1.75–2.03 times as long as second flagellomere. Second flagellomere 1.52–1.68 times as long as wide. Median ocellus vestigial or absent, lateral ocellus touching compound eye. Length / width of clypeus 1.16–1.34. Antepenultimate segment 0.13–0.15 mm long, palpomere ratios 1: 1.06–1.21: 2.24–2.57.

Thorax. Mesonotum length 1.08–1.24 mm, or 0.31–0.33 x as long as wing. Proepisternum with 2–3 strong bristles.

Wings. Wing length to length of R1 2.23–2.32; wing length to length of R5 1.74–1.81. Length of r-m to length of M-petiole 1–1.27. R4+5-bending index 0.93–1. Fork length ratio 0.77–0.86. Fork width ratio 0.78–0.95. M-ratios 0.54–0.61 and 0.6–0.67. CuA-ratios 1.16–1.4 and 1.45–1.95. CuP length to length of wing 0.43–0.46. A1 length to length of wing 0.31–0.33.

Legs. Leg ratios given for fore, mid and hind leg: LR 1.09–1.18: 0.89–0.92: 0.65–0.69; SV 1.59–1.69: 1.95–2.01: 2.48–2.65; BV 1.58–1.68: 2.02–2.14: 2.99–3.2; TR 1.58–1.67: 1.75–1.78: 1.97–2.03.

Terminalia ( Fig. 10 D). Tergite VII excavated dorsally, with strongly dentate to laciniate 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, 2.82–3.2 as long as wide in lateral view. Postgenital plate (gonapophysis IX) elongated, with obtuse tip. Sternite VII subequal in length to tergite VII. Sternite VIII obtuse. Gonapophysis VIII weak, narrow.

Distribution. Palaearctic, mainly northwesterly in Europe.

Biology. Breeding sites unknown, but shown by Kjaerandsen (1993) to be a common cave dweller during wintertime in western Norway.

Type material examined: ENGLAND ( U.K.): Wales, Gwynedd (Merioneth), Brithdir, near Dolgellau, 52°45'10"N, 003°49'26"W, 23 May, 1972 (Leg. A. M. Hutson) [ BMNH, JKJ – SPM –005282].

Additional material examined: DENMARK: Unlabelled, undated ( ZMUC, Leg. C. Staeger) — 1 female (paralectotype of M. trivittata , var. b); ESTONIA: Tôrva, Helme Cave [old refuge cave in sandstone], 58°01'00"N, 025°53'00"E, 19 Jan 1996 ( MZLU, Leg. O. Kurina) — 1 female; FINLAND: Ab, Karislojo ( MZH, Leg. R. Frey) — 1 female; Kuustö ( MZH, Leg. C. Lundström) — 1 female; Sammatti ( MZH, Leg. J. Sahlberg) — 1 male; Ka, Vehkalahti, 29 Aug 1972 ( MZH, Leg. L. Tiensuu) — 1 male; 1 May 1973 ( MZH, Leg. L. Tiensuu) — 1 male; N, Helsinge ( MZH, Leg. R. Frey) — 1 female; Oa, Wasa ( MZH, Leg. R. Frey) — 1 male; Sa, Joutseno, 30 Sep 1965 ( MZH, Leg. E. Thumeberg) — 2 males; Ta, Ruoveri, Ryivärinkuoppa, 20 Sep 1965 ( MZH, Leg. R. Tuomikoski) — 1 female; 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) — 2 females, 2 males; Kvinnherad, Atramadalen, in mine galleries, 60°2'1''N, 5°52'35''E, 9 Mar 1991 ( MZLU, Leg. J. Kjaerandsen) — 5 females, 4 males; Kvinnherad, Fugleberg, in man-made soapstone caves, 60°0'41''N, 5°51'24''E, 9 Mar 1991 ( MZLU, Leg. J. Kjaerandsen) — 3 females, 1 male; Voss, Nesheimstunet, 60°49'08"N, 006°27'59"E, in cellar, 4 Apr 1992 ( MZLU, Leg. J. Kjaerandsen) — 1 male; HOY, Bergen, Haukeland, in mine galleries, 60°21'16''N, 5°27'19''E, 11 Oct 1990 ( MZLU, Leg. J. Kjaerandsen) — 14 females, 16 males; 4 Nov 1990 — 14 females, 6 males; 2 Dec 1990 — 24 females, 7 males; 12 Jan 1991 — 20 females, 18 males; 17 Feb 1991 — 2 females; Bergen, Riple, in mine galleries, 60°18'51''N, 5°26'33''E, 27 Oct 1990 ( MZLU, Leg. J. Kjaerandsen) — 18 females, 19 males; 9 Dec 1990 — 61 females, 59 males; 17 Feb 1991 — 4 females, 2 males; 21 Mar 1991 — 7 females, 2 males; Bergen, Gymmeland, in mine galleries, 60°18'6''N, 5°27'1''E, 9 Dec 1990 ( MZLU, Leg. J. Kjaerandsen) — 4 males; 3 Feb 1991 — 3 females, 5 males; 4 Mar 2001 — 2 males; Bergen, Trengereid, in mine gallery, 60°25'20''N, 5°37'34''E, 22 Jan 1991 ( MZLU, Leg. J. Kjaerandsen) — 6 females, 3 males; Vaksdal, Langhelle, in limestone cave ( MZLU, Leg. J. Kjaerandsen) — 3 females, 1 male; Bergen, Trollhaugen, in unfinished road tunnel, 60°19'10''N, 5°20'2''E, 8 Nov 1991 ( MZLU, Leg. J. Kjaerandsen) — 1 female, 4 males; Bømlo, Hidle, in mine gallery, 59°43'39''N, 5°14'36''E, 10 Feb 1991 ( MZLU, Leg. J. Kjaerandsen) — 5 females; Osterøy, Skaftå, in mine galleries, 60°27'21''N, 5°37'21''E, 8 Nov 1990 ( MZLU, Leg. J. Kjaerandsen) — 2 females, 1 male; Osterøy, Skistad, in mine galleries, 60°30'6''N, 5°32'20''E, 8 Nov 1990 ( MZLU, Leg. J. Kjaerandsen) — 49 females, 39 males; Stord, Litlabø, in mine gallery, 59°47'29''N, 5°25'9''E, 11 Feb 1991 ( MZLU, Leg. J. Kjaerandsen) — 8 females, 5 males; Sveio, Førde, in scree-cave called "Islandshola", 59°36'14''N, 5°26'54''E, 4 Jan 1992 ( MZLU, Leg. J. Kjaerandsen) — 1 female, 1 male; Sveio, Førde, in screes and fissures, 59°36'45''N, 5°28'57''E, 2 Jan 1992 ( MZLU, Leg. J. Kjaerandsen) — 2 females, 1 male; Ølen, Dreganes, in mine galleries, 59°38'34''N, 5°47'32''E, 27 Dec 1990 ( MZLU, Leg. J. Kjaerandsen) — 5 females; 5 Jan 1992 ( MZLU, Leg. J. Kjaerandsen) — 2 males; MRI, Sunndal, Jordalsgrenda, Jordalsøra, Hamrene, 62°46'18"N, 008°19'12"E, 140 m a.s.l., 15 Sep–6 Oct 2005 ( MZLU, Leg. J. B. Jordal) — 1 female; 23 Oct–11 Nov 2005 — 1 female; 11 Nov–1 Dec 2005 — 1 female, 1 male; RY, Haugesund, Vikse, in mine gallery, 59°28'44''N, 5°18'22''E, 11 Nov 1990 ( MZLU, Leg. J. Kjaerandsen) — 3 females, 1 male; 9 Feb 1991 (Leg. J. Kjaerandsen) — 1 male; TRY, Tromsø, Tromsø, Folkparken, 69°38'11''N, 18°54'27''E, 26 Aug 1987 ( MZLU, Leg. G. E. E. Søli) — 1 male; SWEDEN: JÄ, Åre, Mullfjället, 63°25'28''N, 12°55'39''E, 29 Jul 1840 ( MZLU, Leg. J. W. Zetterstedt) — 1 male; LU, Jokkmokk, Porsitjärn/Porsi VVO, 1.5 km SE Vuollerim, 60 m a.s.l., 66°25'28''N, 20°40'17''E, 14 Apr–18 Oct 2003 ( MZLU, Leg. M. Karström) — 1 male; 6 May–13 Aug 2004 ( MZLU, Leg. M. Karström) — 1 female; 13 Aug–13 Oct 2004 ( MZLU, Leg. M. Karström) — 1 female; 15 May–1 Jun 2005 ( MZLU, Leg. K. Hedmark & M. Karström) — 1 female, 3 males; 1–16 Oct 2005 ( MZLU, Leg. K. Hedmark & M. Karström) — 2 females; Jokkmokk, Bombmurkleskogen VVO, 4 km SSE Messaure, 85 m a.s.l., 66°38'47''N, 20°22'49''E, 10 Jun 2006 ( MZLU, Leg. J. Kjaerandsen) — 1 male; SK, Häckeberga NR, 55°35'40.72"N, 13°25'14.56"E, 3 Oct 2004 ( MZLU, Leg. J. Kjaerandsen) — 1 female, 1 male; RUSSIA: Vib, Metsäpirtti, 6 Oct 1935 ( MZH, Leg. Krogerus) — 1 female.

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 10. Pseudexechia aurivernica Chandler, 1978. — A. Male terminalia, ventral view. — B. Male gonostylus, internal view, enlarged. — C. Male tergite IX and cerci, dorsal view. — D. Female terminalia, lateral view.