Dissodesma tetratricha ( Walker, 1849 ) Li & Yeates, 2020

Li, Xuankun & Yeates, David K., 2020, Revision of the Australian bee fly genus Meomyia Evenhuis, 1983, with description of three new species (Bombyliidae, Bombyliinae, Bombyliini), Zootaxa 4810 (2), pp. 201-243 : 238-242

10. Dissodesma tetratricha ( Walker, 1849) comb. nov.

( Figs 24–26 )

Bombylius tetratrichus Walker, 1849: 291 . Type locality: Australia (WA), Holotype, NHMUK.

Type specimen. Holotype of Bombylius tetratrichus Walker , ♀ ( NHMUK 010921903 ) ( Fig. 24 ).

Other specimens examined. Australia, WA, ♂ (1) ♀ (1), Waroona , 5 Mar 1909, GF Berthoud. ♀ (2), Waroona, 10 Mar 1909, GF Berthoud. ♀, Waroona, 11 Mar 1909, GF Berthoud. ♀, Waroona, 16 Mar 1909, GF Berthoud. ♀, Waroona, 15 Feb 1909, GF Berthoud. ♂, Waroona, 20 Feb 1909, GF Berthoud. ♀, Waroona, 25 Feb 1909, GF Berthoud. ♂, Waroona, 13 Mar 1909, GF Berthoud ( NHMUK 010921905 ) . ♀, Waroona, 10 Mar 1909, GF Berthoud ( NHMUK 010921906 ) .

Redescription. Male. Body length 8.6–12.2 mm, wing length 7.5–10.7 mm.

Head. Head about 1.6 x wider than long, mostly blackish with thick white pruinescence and covered in admixed white to pale yellow scales and hairs. Eye holoptic. Frons long, 3.8 x length of ocellar tubercle, upper narrow and black; lower half triangular, 2.3 x length of upper half, with thick pale pruinescence and pale yellow hairs. Ocellar tubercle slightly raised, blackish brown to black with grey pruinescence, with short yellow hairs. Face with thick white pruinescence and long white scales and hairs. Gena with thick white pruinescence and long white hairs. Clypeus with thick pale pruinescence and otherwise bare. Occiput with thick white pruinescence and dense pale yellow scales, except more white scales on ventral half. Posterior eye margin slightly concave. Antennal scape and pedicel black, scape with thick pale pruinescence and long pale yellow hairs, pedicel with sparse pale pruinescence and short pale yellow hairs; flagellum black without pruinescence. Scape 3.1 x as long as wide, and 3.3 x as long as pedicel, uniform from base to apex. Pedicel 1.0 x as long as wide. Flagellum 10.2 x as long as wide, 1.8 x as long as scape + pedicel, 2.3 x as long as scape, conical and slightly laterally compressed, one-segmented with apical stylus. Palpus short, not extending beyond oral cavity, yellow with short yellow hairs, one-segmented, without palpal pit. Mouthparts slender, 4.0 x as long as eye length, 2.5 x as long as head length, labellum thin and filiform ( Fig. 25h ).

Thorax. Integumental colour of scutum mostly black with thick grey pruinescence. Scutum covered with pale yellow hairs, pale yellow hairs darker apically. Three yellow notopleural setae present. Scutellum black with sparse pale pruinescence, covered with long yellow hairs, posterior margin admixed with some strong black hairs. Pleura black with thick pale pruinescence, mostly covered in long pale yellow hairs, except anepimeron, meron, laterotergite and mediotergite bare.

Legs. Legs mostly blackish brown except fore and mid femora dark yellow apically, fore and mid tibiae yellow. Femora covered in pale yellow scales, ventral face with long pale yellow hairs. Hind femur with one row of anteroventral yellow bristles. Mid and fore tibiae covered in pale yellow scales, anterior face admixed with some brown scales on apical half. Other bristles and hairs on legs brownish yellow. Fore tibia 1.7 x longer than fore basitarsus, mid tibia 2.4 x longer than mid basitarsus, hind tibia 2.3 x longer than hind basitarsus.

Wings. Wing membrane clear, slightly darker towards wing base and along costa. Cell r 5 narrowly open; cell br nearly as long as cell bm, crossvein r-m arising from base of cell dm; crossvein m-m nearly as long as crossvein r-m; cell cua open. Haltere stem dark yellow, knob yellow.

Abdomen. Integumental colour of tergites black mostly with sparse grey pruinescence. Tergite 1 with dense yellow hairs; tergites 2 to 4, and 7 to 8 with yellow hairs, admixed few long black hairs laterally and on posterior margin; tergites 5 and 6 admixed with dense long black hairs laterally. Sternites black except posterior margin yellow, with thick pale pruinescence, covered with pale yellow scales and hairs. Genitalia. Epandrium wide and short, anterior margin nearly straight, posterior margin strongly concave ( Fig. 26d ). Hypandrium present. Gonocoxal apex with slightly narrower than the base in dorsal view, ejaculatory apodeme small ( Figs 26 a–b); gonocoxal apodeme strong and incurved; lateral ejaculatory process strong; inner apex of gonocoxite acute, slender and elongate; outer apex of gonocoxite acute, normal length; dorsal bridge without lateral hollow; gonostylus normal; phallus straight, slightly shorter than gonocoxite ( Fig. 26c ).

Female. Body length 8.0– 14.1 mm, wing length 7.7–13.5 mm. Very similar to male, except frons black with thick pale pruinescence, 3.0 x as wide as ocellar tubercle, frons with short white to pale yellow scales on lower half, long pale yellow hairs on upper half, admixed with some long black hairs ( Fig. 25f ). Tergite 8 with thick hairs, eight acanthophorite spines present on each side of tergite 9+10, slightly curved apically. Genital fork slender and straight, connect at apex. Sperm pump strong and long, with some lateral papillae; distal spermathecal duct of normal length, thickened in apical half; spermatheca small and nearly spherical, apex rounded ( Fig. 26g ).

Remarks. Bombylius tetratrichus was placed in the genus Sisyromyia White by Roberts (1928), and was later moved to Meomyia by Evenhuis & Greathead (1999).

We examined the holotype from NHMUK, and there are several specimens in a very good condition. However, all the specimens of Bombylius tetratrichus in ANIC were in poor condition. We were able to identify these specimens and dissect the genitalia of both male and female.

Based on the external and genitalia characters of both male and female, this species belongs to the genus Dissodesma Bowden & Li ( Li & Yeates, 2018) . Therefore, Dissodesma tetratricha is a new combination proposed in the present study.

Distribution. Australia (WA).

Figures

FIGURE 24. Dissodesma tetratricha (Walker, 1849) comb. nov. Holotype of Bombylius tetratrichus Walker, (NHMUK 010921903). (a) dorsal; (b) lateral. Scale bars = 1 mm.

FIGURE 25. Dissodesma tetratricha (Walker, 1849) comb. nov. External (a–c (♂); d–f (♀)): (a, d) dorsal; (b, e) lateral; (c, f) head, profile. Scale bars = 1 mm.

FIGURE 26. Dissodesma tetratricha (Walker, 1849) comb. nov. Genitalia (a–e (♂); f, g (♀)): (a) genital capsule, dorsal; (b) genital capsule, ventral; (c) genital capsule, lateral; (d) epandrium, dorsal; (e) epandrium, lateral; (f) sternite 8, ventral; (g) genitalia and spermathecae. Scale bars = 0.1 mm.