Isocanace australis Mathis 1982

Isocanace australis

DIAGNOSIS.—Specimens of this species are similar to those of I. flava but are separable from them and closely related congeners by the following combination of characters: branching rays of arista shorter, at most slightly longer than basal aristal width; anterior notopleural bristle present, although weaker than posterior bristle; mesopleural and sternopleural bristles black; surstylus in lateral view narrow, with subapical posterior swelling bearing several pale setae, apical one-third curved posteriorly.

DESCRIPTION.—A small beach fly species, length 1.58 to 1.94 mm.

Head (Figure 33): Two large setae along lateral margins of mesofrons, posterior one inclinate, anterior one mostly proclinate, inserted at about same level as fronto-orbital bristles; mesofrons moderately tomentose, becoming more thinly so anteriorly, with grayish brown to brown coloration, quite distinct from parafrons; midportion of mesofrons with 2 rows of about 5 setulae, extending from medial ocellus to anterior margin of mesofrons; postocellar setae distinct, about one-half length of ocellar bristles, proclinate and slightly divergent; parafrons grayish to blackish, appearing dull and membranous; arista minutely plumose, branching rays at most slightly longer than basal aristal width; anaclinate genal bristles 3.

Thorax: Acrostichal setulae in about 4 irregular rows anteriorly and posteriorly, with approximately 11–15 setulae per row, posterior pair of setulae slightly but distinctly larger than other setulae; scutellum with 2 pairs of subequal, lateral bristles, or apical pair only slightly larger; anterior notopleural bristle present but smaller than posterior bristle, sometimes pale; propleuron bare of setulae; sternopleural and mesopleural bristles present, subequal, both usually black; hind tibia lacking apical anteroventral bristle.

Abdomen: Male terminalia as in Figure 34 and as described in “Diagnosis.”

PRIMARY TYPE MATERIAL.—Holotype male is labeled “Port St. Johns South Africa B. & P. Stuckenberg 20–25 Nov. 1961//HOLOTYPE Isocanace australis Mathis [red, handwritten].” The holotype is double mounted (minute nadel in polyporus block), is in good condition (a few setae misoriented), and is deposited in the Natal Museum, Pietermaritzburg, South Africa.

Other Types: Allotype and three paratypes (1, 2) with the same locality data as the holotype. One male and one female paratype are in the National Museum of Natural History, Smithsonian Institution, Washington, D.C.

ZOOGEOGRAPHIC DISTRIBUTION.—This species is known only from the type-locality.