Pseudexechia trivittata ( Staeger, 1840 )

Kjaerandsen, Jostein, 2009, The genus Pseudexechia Tuomikoski re-characterized, with a review of European species (Diptera: Mycetophilidae), Zootaxa 2056, pp. 1-45 : 38-41

Pseudexechia trivittata ( Staeger, 1840)

(Figs 3C 15A–D)

Mycetophila trivittata var. a Staeger, 1840:261

= Exechia pulchrigaster Santos Abreu, 1920:90. Syn. by Chandler & Ribeiro (1995) Exechia trivittata dark form; Lundström 1909:41, fig 68b

Exechia trivittata ; Dziedzicki 1915:14, figs 240–242

Exechia trivittata ; Stackelberg, 1969:299 [in English translation page 453, figs 185,2a&b] Pseudexechia trivittata ; Chandler 1978:44, figs 4 & 7

Pseudexechia trivittata ; Ostroverkhova, 1979:169, fig. 32,4

Pseudexechia trivittata ; Chandler & Ribeiro 1995:67, figs 40a–c Pseudexechia trivittata ; Krivosheina et al. 1986:155, figs 45,2 & 45,8 Pseudexechia trivittata ; Zaitzev 2003:193, figs 43,3 & 43,5

Diagnostic characters. A dull brown species with a distinct greyish dusting and fused, hardly discernable thoracic stripes. Distinctive features of the male terminalia include the ventral branch of the gonostylus being smaller than the dorsal branch, the former being almost devoid of seta on the medial surface while the latter is covered with medial setae. Females have almost identical terminalia with P. tristriata , but can be distinguished by the dull coloration.

Description. Male (n = 5, except where otherwise stated). Total length 3.5–5.4, 4.5 (n=10) mm. Wing length 3.1–3.44, 3.27 mm, or 3.15–3.52, 3.26 x as long as profemur. Antenna 1.34–1.6, 1.48 mm long.

Coloration (specimen in alcohol). A dull brown species with a distinct greyish dusting, mouthparts dark; mesonotal stripes fused, hardly discernable, dark; humeral area dark. Wings with an indistinct spot at base of posterior fork and greyish tinted 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 all dark; terminalia dark yellow.

Head. Width / length to frontal tubercle 1.35–1.64, 1.47. First flagellomere 1.78–2.15, 1.93 times as long as second flagellomere. Second flagellomere 1.5–2.06, 1.75 times as long as wide. Median ocellus vestigial or absent, lateral ocellus touching compound eye. Length / width of clypeus 0.92–1.21, 1.08. Antepenultimate segment 0.09–0.12, 0.11 mm long, palpomere ratios 1: 1.28–1.61, 1.44: 2.69–3.65, 3.03.

Thorax. Mesonotum length 0.92–1.08, 1.02 mm, or 0.3–0.32, 0.31 x as long as wing. Proepisternum with 2 strong bristles.

Wings (Fig. 3C). Wing length to length of R1 2.28–2.4, 2.34; wing length to length of R5 1.73–1.8, 1.76. Length of r-m to length of M-petiole 1–1.2, 1.11. R4+5-bending index 1.04–1.32, 1.14. Fork length ratio 0.77–0.81, 0.8. Fork width ratio 0.8–1.21, 1. M-ratios 0.58–0.63, 0.62 and 0.65–0.71, 0.69. CuA-ratios 1.39–1.51, 1.45 and 1.88–2.14, 2.01. CuP length to length of wing 0.44–0.49, 0.47. A1 length to length of wing 0.31–0.36, 0.34.

Legs. Leg ratios given for fore, mid and hind leg: LR 1.13–1.15, 1.13: 0.84–0.87, 0.86: 0.65–0.7 (n=4); SV 1.6–1.66, 1.62: 2.01–2.08, 2.04: 2.49–2.63 (n=4); BV 1.62–1.7, 1.66: 2.07–2.15, 2.1: 2.88–3.05 (n=4); TR 1.53–1.66, 1.58: 1.69–1.74, 1.72: 1.85–2 (n=4).

Terminalia ( Figs 15 A–C). Gonocoxite subrectangular, with indistinct condyles; sternal sclerite forming longitudinal suture. Hypandrial lobe long, parallel sided, with blunt apices and small split. Aedeagal guides elongated, lying dorsad of internal branch of gonostylus. Gonostylus large, elongated; dorsal branch elongated, oblong, without whitish tip; dorsointernal branch reduced to hyaline, bifurcate knob basally on dorsal branch; medial branch reduced or fused with internal branch; ventral branch forming slender, curved spatula, covered with setae on lateral side, apex with some tight short spines forming a brush, devoid of setae mesally; internal branch forming small, striated cushion; anterior branch forming hyaline, irregular plate with many small, blunt projections caudally. Tergite IX long subrectangular, fused, with weak mesal suture. Pseudocercus medium sized, setose. Cercus forming small knob, 1.44–1.83, 1.58 as long as wide in dorsal view. Hypoproct triangular, acute. Epiproct vestigial or absent.

Female (n = 5, except where otherwise stated). Total length 4.2–5, 4.6 (n=10) mm. Wing length 2.82–3.68, 3.29 mm, or 3.2–3.41, 3.32 x as long as profemur. Antenna 1.1–1.44, 1.32 mm long.

Coloration. As in male except tergite VII dark with subapical pale spot.

Head. Width / length to frontal tubercle 1.28–1.46, 1.39. First flagellomere 1.78–2.15, 1.91 times as long as second flagellomere. Second flagellomere 1.44–1.82, 1.55 times as long as wide. Median ocellus vestigial or absent, lateral ocellus touching compound eye. Length / width of clypeus 1–1.23, 1.14. Antepenultimate segment 0.08–0.12, 0.11 mm long, palpomere ratios 1: 1.23–1.5, 1.38: 2.5–3.68, 3.

Thorax. Mesonotum length 0.88–1.14, 1.02 mm, or 0.3–0.55, 0.36 x as long as wing. Proepisternum with 2 strong bristles.

Wings. Wing length to length of R1 1.33–2.35, 2.09; wing length to length of R5 0.99–1.76, 1.59. Length of r-m to length of M-petiole 0.92–1.27, 1.11. R4+5-bending index 1–1.19, 1.1. Fork length ratio 0.72–0.88, 0.8. Fork width ratio 0.9–1.12, 1.02. M-ratios 0.57–0.64, 0.59 and 0.64–0.71, 0.66. CuA-ratios 0.88–1.76, 1.35 and 1.58–2.55, 1.93. CuP length to length of wing 0.45–0.79, 0.52. A1 length to length of wing 0.31–0.52, 0.37.

Legs. Leg ratios given for fore, mid and hind leg: LR 1.07–1.14, 1.1: 0.71–0.88, 0.81: 0.63–0.71, 0.66; SV 1.61–1.68, 1.65: 2.01–2.46, 2.16: 2.43–2.68, 2.58; BV 1.67–1.74, 1.71: 2.11–2.31, 2.17: 2.9–3.13, 3.02; TR 1.51–1.63, 1.59: 1.47–1.78, 1.69: 1.79–2.08, 1.9.

Terminalia ( Fig. 15 D). Tergite VII excavated dorsally, with slightly dentate to laciniate, acute posterior edge; apicolateral corner without nude area; setae along margin long, slender. Tergite VIII wide, subrectangular. Tergite IX fused with postgenital plate. Cercus one-segmented, short sinusoid with obtuse tip, 2.7–2.88 (n=4) as long as wide in lateral view. Postgenital plate (gonapophysis IX) short, broad, with acute tip. Sternite VII subequal in length to tergite VII. Sternite VIII acute. Gonapophysis VIII strong, broad.

Distribution. Palaearctic, widely distributed in Europe.

Biology. P. trivittata has been reared from fruiting bodies of coprophilous agarics like Coprinus , Psathyrella and Panaeolus ( Jakovlev et al. 2008) .

Lectotype designation. The (remaining) type material in Staeger's type collection at ZMUC consists of 5 males and 7 females. Three of the males and five of the females are P. trivittata according to the prevailing usage of the name, while two males belong to P. tuomikoskii sp. n., one female belongs to P. aurivernica and one female belongs to Exechia cf. fusca Meigen, 1804 . The name P. trivittata conforms to var. a as described by Staeger (with one labelled exception), while the other species in the type series can be attributed to var. b as described by Staeger. In order to secure stability of the name I hereby designate a lectotype for a male in good condition (lacking only parts of some legs) of which I have cleared the abdomen and terminalia and placed glycerine in a microvial on the same pin as the rest of the specimen. In addition one male in the Zetterstedt collection at MZLU is clearly marked as coming form Staeger's collection (Kjaerandsen 2005), belongs to P. trivittata and is regarded to belong to the syntype series, hereafter this specimen is accordingly regarded as a paralectotype.

Type material examined: Lectotype male, DENMARK: Unlabelled, undated, with cleared abdomen in glycerine [ ZMUC, JKJ – SPM –033623, Leg. C. Staeger]. Paralectotypes: same as lectotype — 2 males [ ZMUC, JKJ – SPM –033624–25]; same as lectotype except labelled "Ƥ var. b, Fredrbg" [= Frederiksberg] — 1 female [ ZMUC, JKJ – SPM –033626]; same as lectotype — 4 females [ ZMUC, JKJ – SPM –033627–30]; same as lectotype except with white tag on which "29" is written, labelled: " M. trivittata Staeg. 3 Dania a Staeger" (Leg. C. Staeger) — 1 male [ MZLU, in coll. Zetterstedt, JKJ – SPM –005229].

Other material examined: FINLAND: Ab, Karislojo ( MZH, Leg. R. Frey) — 2 males; Runsala ( MZH, Leg. W. Hellén) — 1 male; Kb, Koli, 18 May 1964 ( MZH, Leg. R. Tuomikoski) — 6 females, 5 males; Le, Enontekis ( MZH, Leg. R. Frey) — 1 female; N, Sibbo, Kitö ( MZH, Leg. G. Stenius) — 1 female; Oa, Wasa ( MZH, Leg. R. Frey) — 1 female; ObS, Uleåborg ( MZH, Leg. W. Uorentaus) — 1 male; Ta, Kalvola, 21 Jun 1943 ( MZH, Leg. V.G. Borg) — 1 male; Torhola, Skogsbybruk, 1 Oct 1965 ( MZH, Leg. K. Mikkola) — 1 male; Urjala, 16 Oct 1965 ( MZH, Leg. R. Tuomikoski) — 3 males; Lammi, Trailing area Evo, Burnt clear-cut area with retention trees, Evo, trap no. 7, 3–15 Oct 2003 ( MZH, Leg. J. Jakovlev) — 1 male; Evo, trap no. 9 ( MZH, Leg. J. Jakovlev) — 1 male; NORWAY: AK, Nesodden, Fagerstrand, 59°44'17"N, 010°35'43"E, 29 Sep 1990 ( MZLU, Leg. S. Kobro) — 1 male; Oslo, Gjelleråsen, Svarttjern, 59°58'42"N, 010°56'39"E, 19 Sep 1992 ( MZLU, Leg. J. Kjaerandsen) — 1 female; SWEDEN: DR, Säter, Säterdalen, Näsåkerspussen, 67°32'47"N, 015°37'45"E, trap id. 10–401, 16 Sep–14 Oct 2003 (Leg. Swedish Malaise Trap Project, NHRS) — 1 male; LU, Jokkmokk, Porsitjärn/Porsi VVO, 1.5 km SE Vuollerim, 60 m a.s.l., 14 Apr–18 Oct 2003 ( MZLU, Leg. M. Karström) — 1 male; 13 Aug–13 Oct 2004 ( MZLU, Leg. M. Karström) — 1 female, 3 males; 1–15 May 2005 ( MZLU, Leg. K. Hedmark & M. Karström) — 1 female; 15 May–1 Jun 2005 ( MZLU, Leg. K. Hedmark & M. Karström) — 1 male; 16 Sep–1 Oct 2005 ( MZLU, Leg. K. Hedmark & M. Karström) — 1 female; 1–16 Oct 2005 ( MZLU, Leg. K. Hedmark & M. Karström) — 4 females, 4 males; HA, Enslöv, Årnilt, 12 May 1972 ( MZLU, Leg. H. Andersson) — 1 male; SK, Blentarp, Stampenbäcken, 55°35'53''N, 13°33'12''E, 11 Oct 1969 ( MZLU, Leg. B. W. Svensson) — 1 male; 6 Nov 1969 ( MZLU, Leg. B. W. Svensson) — 1 male; Häckeberga NR, 55°35'35''N, 13°25'32''E, 29 Sep 1988 ( MZLU, Leg. L. Huggert) — 1 male; SÖ, Haninge, Tyresta National Park, 59°10'44''N, 18°18'51''E, 5 Jun–14 Jul 2000 ( NHRS, Leg. B. Viklund, L. O. Wikars & H. Ahnlund) — 1 female. FRANCE: Val d´Orha miniére (S. O.) au pied d'une haie (PJ), 9 Jul 1968 ( MNHN, Leg. Couturier) — 3 females, 1 male; RUSSIA: Kamtschatka, Bolscherjetsk, 52°53'34"N, 157°02'30"E, 26–27 Jun 1917 ( MZH, Leg. Y. Wuorentaus) — 1 male.

Figures

FIGURE 15. Pseudexechia trivittata (Staeger, 1840). — A. Male terminalia, ventral view. — B. Male gonostylus, internal view. — C. Male tergite IX and cerci, dorsal view. — D. Female terminalia, lateral view.