Cydistomyia brevior (Walker)

Mackerras, I. M., Spratt, D. M. & Yeates, D. K., 2008, Revision of the horse fly genera Lissimas and Cydistomyia (Diptera: Tabanidae: Diachlorini) of Australia, Zootaxa 1886 (1), pp. 1-80 : 69-72

Cydistomyia brevior (Walker)

( Fig. 49 )

* Tabanus brevior Walker, 1848: 188 ; Froggatt 1911: 13, 1915: 14; Ricardo 1915 a: 279; Taylor 1919: 57; Ferguson & Hill 1920: 465; Ferguson 1921 a: 373; Surcouf 1921: 63; Hardy 1944: 84; Chainey, 1990: 251. Holotype female, from Port Essington, NT (BMNH).

Cydistomyia brevior ; Mackerras, 1959: 169; Daniels, 1989: 286; Bickel & Elliot, 1998 -2005: 3.

Tabanus marginatus var. β. Walker, 1848: 189; Ricardo 1915 a: 279 (syn. of brevior Walker ) (see Remarks); Hardy 1944: 84; Mackerras 1959: 169 (both as syn. of brevior Walker ), Chainey, 1990: 285. Specimen from Port Essington, NT (BMNH). (The true * marginatus Walker, 1848 is a Mesomyia ).

* Tabanus anellosus Summers, 1912: 226 ; Austen 1914: 266 (syn. of brevior Walker ); Ricardo 1915 a: 279; Ferguson & Hill, 1920: 465: Surcouf, 1921: 63; Mackerras 1959: 169. (all as syn. of brevior Walker ); Chainey, 1990: 244. Syntypes, three females, from Darwin, NT, S.L. Strangman (BMNH).

* Tabanus australis Taylor, 1917a: 757 ; Ferguson & Hill, 1920: 465 (syn. of brevior Walker ); Mackerras, 1959: 169 (confirms synonymy). Holotype female, from Stapleton, NT (ANIC)..

* Tabanus crypserythrus Taylor, 1919: 60 ; Ferguson & Hill 1920: 465 (syn. of brevior Walker ) Mackerras, 1959: 169 (confirms synonymy). Syntypes, male and female from near Darwin, NT (ANIC).

Other material examined. 34 ♀, 15 ♂.

Diagnosis. A small yellowish brown species, with pale apical bands on abdominal tergites, narrow frons, relatively elongate bell-shaped callus, preponderantly blackish femora, and with well-defined right angle on vein R 4 but without appendix or with only rudimentary stump on one wing only. (One male has appendices on both wings). With the exception of the occasional brown forms of C. musgravii (which may be due only to age) this species should be readily distinguished from all other named species of Cydistomyia except C. pseudobrevior sp. nov. because of its small size and light brown, almost yellowish colouration. It is distinguished from C. pseudobrevior by the usually well-defined ocellar tubercle and occasional hints of one or two ocellar spots, tapering extension of callus generally reaching to a little above middle of frons, flat subcallus, presence of small dorsal prolongation on pedicel, absence of median triangles in midline on abdominal tergites 2–4. It is distinguished from C. musgravii by absence of narrow green band across eye of female, darker more blackish legs, narrower frons with differently shaped callus and narrower basal plate.

Cydistomyia brevior may be confused with three northern forms of Dasybasis Macquart. However , it is distinguished from D. clavicallosa forma darwinensis (Taylor), D. constans (Walker) and D. germanica (Ricardo) by the absence of an appendix on vein R 4 or its presence on one wing only and in the form of a rudimentary stump, presence of an ocellar tubercle, narrower frons, differently shaped callus which is almost full width of frons at base, and abdominal colouration. The legs of D. calvicallosa forma darwinsensis and D. constans are pale but those of D. germanica are frequently dark like C. brevior . Tergites and sternites 1–3 are not so contrasting in colouration in brevior as they are in D. germanica , although the remaining ones are similar. The enlarged upper facets of the eyes of male brevior are bare (hairs barely discernible at 35X magnification) while those of male D. germanica are hairy (easily seen at 15X magnification).

Female. Head. Eyes in life green, bare (few scattered hairs barely visible at 35X magnification). Frons relatively narrow, parallel or slightly divergent, index 4.2–4.4, with pale creamy fawn tomentum and short dark brown hairs; vertex not hollow; vertical triangle ill defined; ocellar tubercle usually well defined, slightly raised, brown, somewhat shiny,; occasionally hints of one or more small ocellar spots; callus brown, slightly narrower than frons at base, bell-shaped, with narrow tapering extension to a little above middle of frons. Subcallus flat, smooth, with a greyish cream tomentum, without hairs; parafacials and face with greyish white tomentum and fawn-white hairs; beard white. Antennal scape subcylindrical, distinctly longer than wide, light yellowish cream, with short black hairs; pedicel about half as long as wide, with small dorsal prolongation, colour and hairs as on scape; basal plate bright brownish orange, with well-defined dorsal angle projecting as small knob, occasionally with few short black hairs at angle; style brownish black. Palpi moderately plump, pale yellowish cream, with creamy white and scattered short black hairs.

Thorax. Scutum and scutellum almost uniformly greyish, paler anteriorly and laterally, with short black and creamy white hairs. Pleura pale grey, with white hairs.

Legs. Femora dark to blackish brown, with variable amount of grey overlay, fore femora with dark brown hairs, mid and hind with creamy to whitish hairs; tibiae light brownish yellow basally, becoming brown towards apex, with dark brown hairs mixed with yellowish cream ones on paler parts; tarsi dark brown, with dark brown hairs. In some specimens almost the whole of the fore leg is dark brown.

Wings. Pale greyish to almost clear, costal cell sometimes faintly yellowish; stigma yellowish brown; veins light yellowish brown, darker apically and distally; cell R 4 wide; vein R 4 angulate, without appendix or at most with a rudimentary stump on one wing only.

Abdomen. First tergite yellowish fawn, 2 nd and 3 rd (sometimes 4 th) light brown, remainder dark brown, all except 7 th with broad light yellowish fawn apical bands; hairs black on darker parts, yellowish cream on paler areas and extending vaguely in mid line on tergites 2–5. Venter darker than dorsum, brownish grey, with conspicuous pale apical bands on sternites; hairs predominantly yellowish cream.

Male. Similar to female but scutum more greyish fawn and abdomen more brightly brownish yellow. Eyes large, bare (hairs just visible at 35X magnification), meeting on almost full length of frons, upper facets greatly enlarged, bright orange-yellow, contrasting with small black lower facets and narrow posterior margin; ocellar tubercle deeply sunken. Antennae more slender than in female. Palpi fusiform, tapering distally, light yellowish cream, with white hairs. In one specimen both wings have a rudimentary appendix on R 4.

Three specimens are placed as Cydistomyia ? brevior (Walker) : 1 male, from Nourlangie Ck, NT, has palpi with mostly white and very few black hairs, the style is not dark and does not contrast with the basal plate, the abdominal colouration is darker, and the abdominal venter is more brown than yellowish or amber; 2 females from Rimbija Island of the Wessel Islands, NT, have more uniform grey-brown abdominal colouration, particularly on the venter, and lack the yellow-brown contrast seen in C. brevior . In one specimen both wings have a rudimentary appendix on vein R 4.

Remarks. Walker (1848) described Tabanus marginatus var. β based upon 2 specimens, “a” and “b”. Examination of these by Miss Ricardo (1915 a) indicated that specimen “a” from New Holland was not var β.

Distribution. Coastal and inland NT from Bathurst Is. to W of Katherine. NT: Bathurst Is., Oct., G.F. Hill; Maningrida, light trap, Mar., J.L. and M. Gressitt; Five Mile Swamp, S of Maningrida, Mar., Gressitt; Gove, M.D. Murray; Berrimah, Jan., D. and A. Daniels; Mar., M.D. Murray; Holmes Jungle, Palm Ck, 15 km NE of Darwin, Mar., J.L. and M. Gressitt; Mudginbarry, Mar., Apr., attacking buffalo, A.L. Dyce; Beatrice Hill, to man, Jan., M.J. Muller; Jabiru, Jan., G. and A. Daniels; Koongarra, 15 km E of Mt Cahill, at light, Nov., Mar., at light, D.H. Colless; U.A.R.R.S. Adelaide R., Mar., A.L. Dyce; Kakadu Nat Pk, nr Jim Jim, Jan., D. Bickel; 20 km S of Adelaide R., Feb., R. Eastman; Brock's Ck, Jan., T. Campbell; Mt Burrell Feb., R. Eastman; Umbakumba, Groote Eylandt, Apr., R.R.Miller; 20 Mile Siding, Mar., G.F. Hill; 100 km W of Katherine, Jan., A. Zwick;

Figures

FIGURES 49–51. 49. Cydistomyia brevior (Walker) frons, antenna, palp, female terminalia, sternite 8, spermathecal bulb. 50. Cydistomyia pseudobrevior Mackerras & Spratt, sp. nov. frons, antenna, palp, female terminalia, sternite 8, spermathecal bulb. 51. Cydistomyia griseicolor (Ferguson & Hill) frons, antenna, palp, female terminalia, sternite 8, spermathecal bulb.