Hesse (1969) redescribed this species as follows: Body in male entirely back, the abdomen also entirely black, and the legs very much darker, even tibiae darker; body in female also entirely black, and tibiae also darker than in female A. callosus var. thorni. Integument in both sexes with the same parts shining, but abdomen in yyyyy bove more sparsely punctured, distinctly less densely 'nadelrissig', and last two tergites distinctly less transversely wrinkled; integument of thorax above as in A. callosus; that of abdomen in female above even more sparsely punctured, the last two tergites distinctly more finely and more densely transversely striate, and with fewer or less dense puncturation across hind margin of last tergite. Vestiture with the hairs in male very similar to those of var. thorni, but fine ones on abdomen relatively sparser and slightly shorter; hairs on head in female distinctly much longer, mainly pale, less dark, and those on clypeus markedly longer, denser and whitish as stated by Macquart, in this respect differing from most other females of this genus; rest of hairs on body similar, but reversed dark ones on last two abdominal segments comparatively shorter; hairs on legs in both sexes similar and similarly coloured. Head with the antennae relatively shorter, but also longer than thorax, and with the segments having more or less the same proportions, but 3 only a little, or scarcely, shorter than club; latter relatively more slender, slightly more conspicuously broadly yellowish across its middle; proboscis relatively shorter, slightly shorter than vertical length of eye. Wings on the whole more darkly tinted, almost blackish, due to more distinct fuscous borders along veins in hind half; veins darker, usually more blackish; other venational characters the same. Legs very similar and also armed with reddish spines and spicules which are similarly arranged; basal segment of hind tarsi comparatively shorter (the tarsus itself relatively shorter), though also longer than claw-segment. Oviscape of female with fewer, only about 6 or 7, more reddish spines on a side. Hypopygium of male with the anal lobes relatively shorter and broader, their apical margins together more rounded, less indented, each lobe being more rounded, less pointed; other hypopygial structures very similar to those of male A. callosus, but the processes more rounded apically. Length of body: about 10.25-11.00 mm; Length of wing: about 8.5 mm.

Both the male and female specimens are almost indistinguishable superficially from A. callosus var. thorni, detailed information on the differences between these species are indicated in the morphological description (Hesse 1969).

Type locality: South Africa, 'Du Cap' (= Cape of Good Hope).

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

South Africa.

South Africa, Western Cape, Ysterfontein near Saldanha Bay (South African Museum, Sept. 1960) among the endemic sclerophyll-type of vegetation occurring there near the sea coast.

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).

Specimens have been collected from September - November (very few records for August and December) (Kirk-Spriggs and Sinclair 2017).

Fynbos.