Pseudexechia monica Kjaerandsen & Chandler, 2006

Kjaerandsen, Jostein, 2009, The genus Pseudexechia Tuomikoski re-characterized, with a review of European species (Diptera: Mycetophilidae), Zootaxa 2056, pp. 1-45 : 27-30

Pseudexechia monica Kjaerandsen & Chandler, 2006

( Figs 11 A–D)

Pseudexechia monica Kjaerandsen & Chandler, 2006:46 , figs 2 A–D

Diagnostic characters: P. monica forms together with P. parallela 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. parallela by unique characters in the male terminalia, including the ventral branch of the gonostylus being angled and widely club shaped, the hypandrial lobe being large subrectangular, elaborate and with a large diverging split apically, and the hypoproct forming a short, strongly downcurved cylindrical process. It shares the shape of the ventral branch of the gonostylus with P. aurivernica Chandler, 1978 , but can easily be separated from this larger species by fused thoracic stripes and other details of the male terminalia such as shape of the hypandrial lobe and the widened apex of the dorsal branch of the gonostylus.

Description. Male (n = 2, except where otherwise stated). Total length 3.9– 3.9 mm. Wing length 2.58–2.6 mm, or 2.77– 3 x as long as profemur. Antenna 1.44–1.62 mm long.

Coloration (pinned specimen). A dull brown species with a distinct greyish dusting; mesonotal stripes fused into dark, broad medial band; humeral area forming broad pale band along margin mesonotum. Wings unmarked, yellowish tinted. Legs all pale. Abdomen dark, usually with triangular pale bands on tergite II–V, tergite VI all dark; terminalia yellow.

Head. Width / length to frontal tubercle 1.31–1.36. First flagellomere 1.87–2.03 times as long as second flagellomere. Second flagellomere 1.72–1.88 times as long as wide. Median ocellus vestigial or absent, lateral ocellus touching compound eye. Length / width of clypeus 1.25–1.28. Antepenultimate segment 0.1–0.11 mm long, palpomere ratios 1: 1.32–1.44: 2.16–2.34.

Thorax. Mesonotum length 0.86–0.9 mm, or 0.33–0.35 x as long as wing. Proepisternum with 2 strong bristles.

Wings. Wing length to length of R1 2.26–2.32; wing length to length of R5 1.7–1.71. Length of r-m to length of M-petiole 1.29–1.36. R4+5-bending index 1.15–1.22. Fork length ratio 0.69–0.72. Fork width ratio 1.08–1.19. M-ratios 0.54–0.56 and 0.59–0.61. CuA-ratios 1.63–1.69 and 2.2–2.36. CuP length to length of wing 0.48–0.5. A1 length to length of wing 0.33–0.33.

Legs. Leg ratios given for fore, mid and hind leg: LR 1.15–1.16: 0.87–0.91: 0.65–0.66; SV 1.6–1.65: 1.97–2.02: 2.58–2.63; BV 1.53: 1.87–1.88: 2.67–2.76; TR 1.54–1.61: 1.66–1.68: 1.78–1.84.

Terminalia ( Figs 11 A–D). Gonocoxite deeply excavated, with distinct condyles; sternal sclerite forming longitudinal suture. Hypandrial lobe large, apically expanded and bi-lobed. Aedeagal guides absent or fused with hypandrial lobe. Gonostylus small, retracted; dorsal branch truncated, with distinctly angled and widely club shaped, whitish tip; dorsointernal branch forming small, subrectangular lamellate fan; medial branch present as small knob with two setae; ventral branch forming narrow, angular boot-shaped, without fan-tipped setae; internal branch forming large, striated cushion; anterior branch forming ventrally directed, subrectangular cushion with three tapered projections caudally. Tergite IX long subrectangular, divided mesally. Pseudocercus short, setose. Cercus forming small knob, 2 (n = 1) times as long as wide in dorsal view. Hypoproct long, acuminate, strongly downcurved apically. Epiproct vestigial or absent.

Female unknown.

Distribution. Known only from Wales in Great Britain.

Biology unknown.

Type material examined: Holotype male, GREAT BRITAIN ( U. K.): WALES, Anglesey, Cors Erddreiniog, 27 July 1988, NCC Peatland Survey, water trap 9, rank Schoenus flushes, [ RSME, Leg. Holmes, Boyce & Reed]. Paratypes: GREAT BRITAIN ( U. K.): WALES, same data as holotype — 1 male; Anglesey, Cors Erddreining, NCC Peatland Survey (water trap 11), 27 July 1988 (Leg. Holmes, Boyce & Reed) — 1 male [ MZLU, JKJ – SPM – 011936, on slide]; Anglesey, Cors Bodeilio, NCC Peatland Survey (water trap 1—Phragmites bed), 26 July 1988 (Leg. Holmes, Boyce & Reed) — 3 males [2 males coll. P. Chandler, 1 male MZLU, JKJ – SPM – 011937, on slide]; Anglesey, Cors Bodeilio, Mar 1990 (Coll. P. Chandler, Leg. A. Godfrey) — 1 male.

Figures

FIGURE 11. Pseudexechia monica Kjaerandsen & Chandler, 2006. — A. Male terminalia, ventral view. — B. Male gonostylus, internal view, enlarged. — C. Male tergite IX and cerci, dorsal view. — D. Hypandrial lobe, ventral view, enlarged.