Ammodaimon acares sp. n.

Figs 1 -11

Derivation. Gr. acares = tiny. Refers to the small size of this species.

Description: Based on holotype ♂.

Head: Antenna (Fig. 3) inserted at about half-way between lower facial margin and top of ocellarium. Scape and pedicel subspherical, silvery pruinose, bearing pale yellowish-white bristles and setae. Pedicel longer and stouter than scape. Third segment (first flagellomere) cylindrical, longer than scape and pedicel combined, thickened basally and gradually tapering distally, and bearing an elongate annulated terminal style (microsegment). Style almost as long as third segment, bearing a short apical bristle. Face blackish, silvery pruinose, gently convex and slightly divergent ventrally (Fig. 2). Mystax long, silvery-white and covering entire surface of face (Fig. 2). Frons almost parallel-sided (slightly divergent dorsally) and similar in appearance to face. Ocellarium with 4 pairs of white ocellar setae. Vertex similar in colour to frons, equipped with about 30 white setae. Eye, in lateral profile (Fig. 3), narrower ventrally than dorsally (occiput more extensive ventrally).

497

Occiput shiny black centrally, silvery pruinose and covered with white setae ventrolaterally. Proboscis black, projecting a little beyond face in lateral aspect and completely hidden by thick mystax when viewed from above. Palpi minute, singlesegmented and with a few white setae.

Thorax: Pleura black, silvery pruinose except for ventral half of anepisternum which is bare and shiny. Katatergite bears many long, white setae. Upper half of anepisternum and katepisternum with shorter, broader, white setae. Anatergite without setae, black, silvery pruinose. Mesonotum shiny black, with most of central part silvery pruinose (Fig. 1). Postpronotal lobe shiny black with a single white bristle dorsally. 3 notopleurals (1 ventrally placed, 2 dorsally); 1 supra-alar; 1 postalar; all long, whitish. 4 pairs white dorsocentral bristles (Fig. 5); scutellum shiny black with lateral patches of silvery pruinescence, 10 white marginal bristles. Halters pale yellow. Wings (Fig. 7); 2,3 X 0,9 mm (length from humeral crossvein; breadth through first fork of radial sector); membrane transparent, unmarked; veins pale brown-yellow. Costa extends, as an ambient vein, around wing margin until lA vein; anal ceV and alula not enclosed by a vein on wing margin. Legs: Black, slender, covered with long white bristles. All segments with flat, white, recumbent setae. Tarsi as long as tibiae, terminating in a pair of long, slightly curved claws (Fig. 6). Pulvilli and empodia absent.

Abdomen: Terga shiny black, posterolateral corners silvery pruinose, bristles and setae white. Sterna similar to terga. Genitalia rotated through 90°, epandriallobes shortish, proctiger jutting out well beyond tips of epandriaJ lobes (Figs 8, 10). Hypandrium tapering towards a slightly bulbous distal end (Figs 8-9) (genitalia illustrated are those of the paratype ♂).

Paratypes: 1 ♂ 12 ♀; ♂ agrees well with holotype but slightly larger (wing 2,4 X 1,0 mm). ♀; very similar to ♂ except for the following points: Setae of antennae, frons and ocellarium yellowish. Mystax yellow, and shorter than antennae, except for setae along lower facial margin which are long and white. Frons, vertex and mesonotum silvery-gold pruinose (frons contrasting with silvery pruinose face). Terga 6-8 entirely black and lacking silvery pruinase posterolateral corners. ♀; genitalia (Fig. 11) with acanthophorites, each bearing 5 stout bristles. Eighth sternite shiny yellow-brown. Females vary little in size (wings: 2,3 x 0,9-3,1 x 1,2 mm).

Material examined: NAMIBIA: 2 ♂ (holotype & paratype) 12 ♀; (paratypes), 30 km NW of Karasburg (2718 DA), 28. viii. 1983, J. Landt & B. Stuckenberg, Arid Karoo type veget. Material deposited in Natal Museum (Type No. NM 2755) except for 2 ♀; one deposited in the State Museum, Windhoek, and one in the British Museum (Natural History), London .

?,

Remarks: This tiny species was found resting on sandy ground on the sunny sides of small woody shrubs in an arid, exposed area probably regularly grazed by sheep or goats. We had been collecting in the area for more than an hour before these minute flies were observed. Individuals flew quickly, close to the ground, and appeared to prefer resting near the bases of shrubs rather than in open unvegetated places. The flies were difficult to get into the net as they tended to remain on the ground, even when the net had been firmly brought down around them. A number of specimens were caught by placing glass tubes over them.