Cydistomyia rivularis (Ferguson & Hill)

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 : 64-66

Cydistomyia rivularis (Ferguson & Hill)

( Figs. 8 , 45 )

* Tabanus pygmaeus Ferguson & Henry, 1920: 842 [Preoccupied by Williston, 1887], Nearctic; Mackerras, 1959: 168 (syn. of rivularis Ferguson & Hill ). Holotype female, from Kendall, NSW (AM).

Tabanus rivularis Ferguson & Hill, 1922: 264 (replacement name for pygmaeus Ferguson & Henry, 1920 ).

Cydistomyia rivularis Mackerras 1959: 168 ; Daniels, 1989: 287; Bickel & Elliot, 1998 -2005: 4.

Other material examined. 93 ♀, 2 ♂.

Diagnosis. More variable in size (length 9–12 mm) than C. musgravii and C. atmophora , C. rivularis is distinguished from them by the presence of a broad dark median vitta on the abdominal sternites. Further distinguished from these species by wider frequently divergent frons (index 3.0–3.6) with numerous black hairs, indistinct vertical triangle, indistinct ocellar tubercle, smaller and usually more rounded callus with or without delicate narrow extension reaching to mid frons, fleshy white to light fawn palps with white hairs sometimes mixed with few black ones apically, light fawn scape and pedicel (latter slightly darker) with few short black hairs only apically and usually dorsally, narrower basal plate without ventra1 swelling and with gently rounded dorsal angle, and continuous row of setulae on vein sc above. It is distinguished from C. innubilus by banded eyes, darkish brown rather than greyish black abdominal colouration, particularly on the venter, wider frons with callus full width of frons at base, shorter fawn-brown rather than greyish black palps, brown legs, less conspicuous stigma and more rounded rather than sharply angulate vein R 4.

Cydistomyia rivularis is also widely distributed but almost invariably associated with rivers and streams in mountains and at low altitudes.

Female. Head. Eyes in life reddish brown, with narrow bright green or blue-green oblique band at level of callus, bare (fine hairs visible at 35X magnification). Frons frequently divergent, index 3.0–3.6, with variegated grey and fawn tomentum, pale grey along eye margins, with numerous short black hairs; vertex not hollow; vertical triangle indistinct; ocellar tubercle indistinct, ocelli not observed; callus shiny, dark brown, bulging, full width of frons at base, more rounded than pyriform, with or without delicate narrow extension arising abruptly and reaching to mid frons. Subcallus smooth, with ashy grey tomentum, without hairs; parafacials and face with ashy grey tomentum and black hairs; beard greyish white. Antennal scape about as wide as long, pale greyish fawn, hairs black; pedicel cup-shaped, with short dorsal prolongation, slightly darker than scape, with black hairs; basal plate brown, without ventral bulge anteriorly and with gently rounded dorsal angle posteriorly; style blackish brown. Palpi pale creamy fawn, with few black hairs.

Thorax. Scutum greyish black with vague, wide, greyish dorsocentral vittae and lateral margins, interrupted by brown stripe above wing root; hairs black and appressed yellowish cream, latter conspicuous only in front of scutellum. Scutellum greyish black, hairs as on scutum. Pleura pale grey, with relatively dense greyish white hairs except for usual mixture of dark ones on upper mesopleural convexity.

Legs. Brown, femora with some greyish overlay, tarsi darkening to blackish brown; hairs greyish white on most of femora, black on anterior surface of fore femora, predominantly black on tibiae, entirely black on tarsi.

Wings. Pale greyish, costal cell not darkened; stigma pale brown, inconspicuous; veins brown; with continuous row of setulae on vein sc above.

Abdomen. Brownish black with black hairs, basal tergites not as dark as apical ones; narrow well-defined pale grey, creamy haired apical bands on tergites 1–5, not widening to form definite median triangles; extreme lateral margins pale, with black hairs basally and creamy white hairs at apical lateral corners on all tergites. Venter grey laterally, contrasting with dark dorsum, with broad dark median vitta on sternites, usually extending from sternites 2–7, in some larger specimens extending only from sternites 2–5, with 6 th and 7 th sternites uniformly dark.

Male. Generally smaller than C. musgravii and distinguished from it by same features distinguishing females. Broad median dark vitta extending from sternites 2–6 on abdominal venter, 7 th sternite uniformly black, with long black hairs. Sparse white hairs on sternites 2–5, short black hairs on 6th sternite. Legs more lightly coloured, fawn-brown, with darker tarsi. Antennae more lightly coloured, scape light fawn with white hairs, especially distally; pedicel light fawn with sparse long white hairs apically mixed with few black hairs apically and dorsally; basal plate narrow, pale orange-brown, with gently curving dorsal angle; stigma darker. Palpi fawn with numerous long white hairs and few short black ones. Vein sc with continuous row of setulae above.

Distribution. Mountain and coastal rivers and streams from N of Emerald QLD through NSW to Warburton VIC. QLD: Valencia, Nov. J.E. Le Souef; Carnarvon Nat. Pk., Nov., D. Bickel, Dec., M.A. Schneider and G. Daniels; Stanley R., Woodford, Mar., I.M. Mackerras; 7 km S of Dayboro, Sept., M. Yall; Camp Mt, Nov., I.M. and M.J. Mackerras; Upper Coomera R., Dec., I.M. and M.J. Mackerras; Nerang R., nr Springbrook Forest, Dec., T.G. Campbell; Tallebudgera Ck, 15 km SSW of Burleigh Heads, Oct., D.J. Cook. NSW: Undercliffe Falls, Jan., F.A. Perkins; Browns Ck, Warrumbungle Nat. Pk., Jan., M.E. Irwin and D.K. Yeates; Wambelong Ck, Gumin, Jan., M.E. Irwin and D.K. Yeates; Murray R., nr Dorrigo, Jan., J.B. Cleland; Kew, Jan.; Chichester SF via Dungog, Dec., B. Cantrell; Kundibakh, C. Dennes; Eccleston, Feb.–Mar., J. Hopson; Allyn R., Dec., G.M. Goldfinch; Blackheath, Feb., A.J. Nicholson; Tuglow R., nr Mt Werong, Dec., G. Daniels; Cox's R., Dec., B. McMillan; Shoalhaven R., nr Tallong, Dec., B. McMillan; Wee Jasper, Jan., M.E. Fuller; Gibraltar Peak, Feb., S.J. Paramonov; Cotter R., Jan., M.E. Fuller, Jeffries, H. Wilson, Cabbage Tree Ck, Clyde Mtn, Jan., D.H. Colless; Queanbeyan R., nr Jerangle, Jan., I.M. Mackerras; Snowy Plains, Feb., D.M. Spratt; Kosciuszko Nat. Pk., Jan., M.J.D. White; Wallagoot Lake, nr Bega; Nadgee Nat. Res., nr Eden, Feb., D. Bickel. VIC: Bright, bred from larva, Dec., R. Lewis; Jamieson, Jan., N. Dobrotworsky; Warburton, Feb., N. Dobrotworsky.

Remarks. A female from Landsborough, Qld, has a brown abdominal venter with singularly indistinct median vitta, and possesses some black hairs both on the antennal scape and pedicel and on the palps and is difficult to place with certainty. In all other characters it agrees with C. rivularis so is tentatively placed here.

Figures

FIGURES 1–8. Habitus images 1. Cydistomyia casuarinae (English, Mackerras & Dyce) wing length 11 mm. 2. Cydistomyia cyanea (Wiedemann) wing 12 mm. 3. Cydistomyia nigropicta (Macquart) wing: 18 mm. 4. Cydistomyia doddi (Taylor) wing 13.5 mm. 5. Cydistomyia magnetica (Ferguson & Hill) wing: 14 mm. 6. Cydistomyia alternata (Ferguson & Hill). 7. Cydistomyia victoriensis (Ricardo) wing: 16mm. 8. Cydistomyia rivularis (Ferguson & Hill) wing: 9mm.

FIGURES 43–45. 43. Cydistomyia victoriensis (Ricardo) frons, palp, antenna, female terminalia, sternite 8, spermathecal bulb. 44. Cydistomyia musgravii (Taylor) frons, palp, antenna, female terminalia, sternite 8, spermathecal bulb. 45. Cydistomyia rivularis (Ferguson & Hill) frons, palp, antenna, female terminalia, sternite 8, spermathecal bulb.