Larvae are saprophagous, coprophagous and necrophagous. Females are kleptoparasitic on spiders and predaceous insects. In a rearing experiment with compost from Gomera the development from egg to adult lasted 4-7 weeks (in Germany) with the the puparium lasting about 2 weeks.
Differs from congeners in the combination of posterior eye margin with notch, shiny black mesonotum, yellow halter and male abdomen with T2-4 slightly brown microtomentose except for shiny black posterolateral edges.
Male coloration and vestiture: frons subshiny black, ocellar triangle and upper orbital plates shiny black, lunule reddish or black, basoflagellomere either completely black or basomedially reddish, face grey microtomentose, palpus black or reddish; thorax with mesonotum shiny black, scutellum brown microtomentose, pleura with anepisternum and middle of katepisternum shiny, otherwise slightly brown microtomentose, wing hyaline, veins yellow, brown spot at tip of vein R1 absent, calypter white, halter yellow, legs black, fore and hind tarsus with yellow brush; abdomen with T2-4 slightly brown microtomentose except for shiny black posterolateral edges, T5 shiny except for anterior margin. Female coloration and vestiture: halter yellow, abdomen with T2-4 medially brown microtomentose, laterally shiny, T5 shiny.
Morphology. Head: frons with 2+1 orbital and 2 frontal setae, anterior frontal seta medioclinate. In males frons 2.5x as wide at posterior margin than at base of antenna, arista about 3.3x as long as basoflagellomere wide, pubescence on arista very short, posterior eye margin with wide notch (5-6oc) and narrow emargination (1-2oc).
Thorax: 2 dc, 1 prsc, 1 pprn, 1(+0.4) prs, 2 keps setae, posterior prsc about as long as posterior dc, seta between posterior prsc and posterior dc absent. Wing with vein R4+5 and M1 strongly converging (6.5), and ultimate section of vein M1 1.5x as long as penultimate section. Fore femur normal setulose, tibial organ absent.
Male abdomen: posteromedial triangular projection of T1 into T2 present. Tergal chaetotaxy: T2 anterolateral corner with more than 3 lines of setae, T2-5 setulose except for anterior half, T5 lateral margins with long setae. S5 1.6x as long as wide, 2.0x as long and 1.5x as wide as S4, roughly rectangular, posterior margin indented, setulose. Male genitalia with apical seta on cercus shorter than longest epandrial seta; pregonite with tuft of strong setulae; epandrium with striate anteroventral extension and 0 setae on subepandrial plate, surstylus 0.3x as long as epandrium high, dilated posteroapically (1.2x), slightly bent anteriorly, straight in posterior view, 1.3x as long as wide, structure of lateral surface striate, medial surface without setulae.
Puparium: elongate, tapering towards anterior and posterior end. Empty puparium orange brown, dull, with distinct borders between segments. Anterior (thoracic) part dorsoventrally compressed with shallow but distinct lateral depressions on both dorsal and ventral side. All thoracic segments sculptured by distinctive, mostly transverse ribs; prothoracic (both dorsally and ventrally) and mesothoracic (dorsally only) segments with more conspicuous ribbed sculpture. Anterior spiracles with 6 spiracular lobes (papillae). Abdominal segments circled by very fine ribs or wrinkles, ventrally each with 1-2 transverse rows of very minute spinulae. Posterior end of puparium more convex and strongly transversely or reticularly (last segment) ribbed. Anus fully visible. Posterior spiracles borne on widely-separated protuberances; each spiracle without peritreme and not on a single plate, but composed of 3 pale yellowish brown, finger-like projections. Each spiracular projection has its own, slightly curved slit and several, little branched and fine, interspiracular processes.
Body length: 2.5-3 mm; wing length: 2.5 mm.
Specimens studied by me (but not databased) were collected on goat, dairy cattle and pig dung, manure piles, grass clippings, garden compost, flowers of Donnellsmithia hintonii M&G., Asclepias, Baccharis glutinosa, Ochradenus baccatus, Tamarix, and leaves of pawpaw, and in Malaise, light, flight, pan, pit fall, carrion, and dung traps. Habitats are arid zones, beach forest, forest edges, mountain meadows and ponderosa pine/meadow. Flies were bred from decaying banana skins and ground-nut plots. Milichiella lacteipennis was observed swarming beside cactus and was attracted by raw or linseed oil or paint.
Species in the lacteipennis-group are characterized by the combination of posterior orbital seta present, shiny black ocellar triangle and orbital plates, 2 dc, 1 prsc, prsc about as long as posterior dc, 1 pprn, vein R4+5 and M1 strongly converging, male halter yellow, seta on subepandrial plate absent, lower half of epandrium striate, surstylus usually longer than wide, with slight angle anteroapically and dilation posteroapically and with lateral side striate.
almost cosmopolitan in warm (mediterranean to tropical) areas