Hesse (1969) described this species as follows: Body almost entirely black, but with a conspicuous yellowish whitish infusion on each side of hind part of pleurae, occupying the area below hind part of pteropleuron, below metapleural tubercle in front of halteres, below halteres, upper part of metasternum and anterior lateral basal angle of tergite-1, this infusion appearing whitish due to conspicuous whitish tomentum which also extends on to dorsal (hinder) half of hind coxae; anterior lateral and posterior lateral parts of tergite-1 and base on sides and extreme lateral margin of tergite-2 also obscurely yellowish brownish, and lower faces of front and middle femora, as well as under-surfaces of hind femora, and hind tibiae infused with dark reddish brownish; hind margin of tergite-1 also obscurely dark reddish brownish, but those of rest of tergites however dark like rest of abdominal surface; bullae dark or blackish. Integument of the head in front, especially clypeus, shining, and tergites 5-8, especially latter, also shining; rest of body, including pleurae, dull; integument of greater part of body and legs covered with minute, areolar microsculpture as in A. bunochilus, less evident on shining parts; that of thorax above vermicellately rugulose as in other species, also in streaks of finer and coarser ones, the sides of thorax above also rugulose, but with slightly more numerous oblique rugae than in A. bunochilus, more like those of A. lightfooti; pleurae distinctly duller, with more evident rugulose microsculpture than in the other two species; metanotum distinctly more coarsely rugulose than in the other species, and tergites 1-3 and base of 4 finely shagreened in appearance, slightly more so than in A. bunochilus; last two abdominal segments transversely wrinkled; proboscis duller, due to microsculpture and with more numerous oblique rugae than in A. lightfooti; integument of legs mainly dull, due to microsculpture as in A. bunochilus, the femora with slightly denser, more evident, transverse annulation than in the other two species. Vestiture as poorly and sparsely developed, the longer hairs on head however slightly longer, snow-whitish on vertex and sides of frons basally, more yellowish brownish on each side of frons anteriorly and on antennal segments 1 and 2 ; hairs on clypeus markedly sparse, the latter almost bare, but the few above and on sides along basal part also yellowish brownish; those on palps and head below also appearing more greyish yellowish or yellowish brownish in certain lights; postvertical, almost bristly, spines yellowish whitish, and rest of hairs on occiput more yellowish brownish; hairs on thorax above in 4 streaks, distinctly longer, but sparser than in A. lightfooti and much longer than in A. bunochilus, entirely silvery white as are also sparse ones on propleurae, the very few on hind part of pteropleuron and sparse ones on metapleural tubercle in front of halteres; sparse hairs on tergites-1 and 2 also whitish, longer anteriorly basally on sides; reversed ones on last two abdominal segments and genital parts dark, appearing more fulvous brownish or brownish in certain lights, but more blackish on genitalia; sides of sternites 1-4 or 5 appearing greyish, due to some distinct greyish or silvery tomentum; sparse and short hairs on femora whitish, appearing more yellowish on sides of hind ones, and denser, relatively longer ones on tibiae mainly pale, but longer ones along inner sides of hind ones darker; spines and spicules on legs dark or blackish. Head with the interocular space on vertex relatively narrower than in A. lightfooti and much narrower than in A. bunochilus, though the space between eyes on head below is narrower than above, it is broader than in A. lightfooti, but narrower than in A. bunochilus; antennae longer than thorax (excluding scutellum), considerably longer than in A. bunochilus, more like those of the other species; segment-1 about 3 times length of 2; segment 3 elongate, relatively longer and stouter than in A. lightfooti, longer than club; the latter shaped more like that of A. lightfooti, however more concavely truncate apically as in A. bunochilus, though not so trapezoidal in shape, thickened in apical half from just before middle and constricted basally; clypeus rather prominent, relatively large, larger than in all the other species, brilliantly shining, relatively longer than and not so shortly tumid as in female A. bunochilus, its apex above more conically pointed; proboscis relatively long, longer than that of A. ightfooti, longer than either the antennae or the thorax, about 3.2 mm long, not reduced as in A. bunochilus, its labella large and ovate; palps minute, but distinct. Wings very darkly infuscated blackish brownish, almost black, slightly less intense or paler in hinder half, with a little less than basal third of first basal cell, middle parts of second submarginal and first posterior cells, alula and hind border (beyond fuscous borders of posterior veins) clearer; apex of first posterior cell angularly subtending on costal margin or only very shortly stalked; apex of discoidal cell stalked; lower vein of anal cell rather markedly sinuous; halteres blackish brown. Legs with the hind femora thickened, less clavately so than in the other two species, the basal part less slender or with a shorter slender part, armed below with a double row of shortish spines; hind tibiae stoutish, but, unlike those of A. bunochilus, armed along outer lateral part with some distinct spicules in addition to those below; basal segment of hind tarsi subequal in length to claw-segment, no longer as in the other two species; claws relatively stouter, especially hind ones, which are also more sickle-shaped. Oviscape with about 7 blackish brown spines on a side. Length of body: about 15 mm; Length of wing: about 11.5 mm.

Arenomydas pleurostictus is another interesting black and black-winged Namaqualand species. It appears to show transitional characters in having affinities both with the Bushmanland species A. lightfooti and the peculiar aberrant Koup Karoo species A. bunochilus, but in certain respects more with the latter, though at the same time having certain distinguishing characters of its own highlighted in the morphological description (Hesse 1969).

Type locality: South Africa, Northern Cape, 24 km north of Steinkopf.

Arenomydas is southern African endemic genus with about 9 described species found mainly in South Africa, with one record from southern Namibia (Kirk-Spriggs and Sinclair 2017).

South Africa.

South Africa, Northern Cape, Namaqualand: 24 km north of Steinkopf (G. van Son, 11th Aug. 1961) (Hesse 1969).

The information below was extracted from Cannings and Scudder (2005): Dipterans are primarily aerial insects and the mesothorax, which bears the only pair of wings, dominates the thorax - the prothorax and metathorax are greatly reduced. The legs are normally rather simple and are used primarily for perching; in some groups, they are modified for prey capture or for signaling during courtship. The tarsi are nearly always 5-segmented. The functional wings are membranous and their pattern of veins is critical in fly classification and identification. During the evolution of flies, there has been a trend towards a reduction in veins, especially in the rear half of the wing – changes that evidently relate to improvements in two-winged flight. The hindwings, present in most other insects, are reduced in Diptera to small, club-like organs, called halteres, used for stabilising flight.

Herbivore - Nectarivore (nectar-eating)

The flies in this family are not known to hunt, catch or prey upon other insects as asilids do, but mainly feed on nectar (Hesse 1969).

Like the others, flies in the Mydidae family begin life as an egg, which hatches into a grub-like larva. Most of the fly life is spent in the larval stage, mainly eating and growing as well as molting several times. Some flies may spend at least a year as a larva. The next stage is a pupa, during which the insect transforms into its final stage, emerging from the pupa as a winged adult, able to mate and reproduce. In many species, males stake out positions at favourable egg-laying sites and wait for females to arrive (Hesse 1969).

Succulent Karoo