Milichiella argenteocincta has been collected at light, in Malaise traps, on shells, on Murraya exotica Millsp. (Rutaceae) leaves, in dirt near Atta cephalotes nests, and from excrement in a toucan's nest.
Differs from congeners in the combination of brown microtomentose mesonotum, grey pleura and silvery posterolateral corners of male T2.
Male coloration and vestiture: frons subshiny black, ocellar triangle and orbital plates shiny black, lunule yellowish, basoflagellomere basomedially yellow, face silvery white microtomentose, palpus yellow, tip sometimes darker; thorax with mesonotum brown microtomentose (sometimes only slightly), scutellum same, pleura slightly grey white microtomentose, wing hyaline or white, veins yellow, brown spot at tip of vein R1 present, calypter white, halter yellow, legs black except for medially and posteriorly yellow fore coxa and ventrally red brown tips of femora, bases of tibiae, and tarsi; abdomen with T2-4 slightly brown microtomentose except for silvery posterolateral margin of T2 and narrow greyish posterior margin of T3-4; T5 shiny except for brown microtomentose anterior margin. Female coloration and vestiture: halter yellow, abdomen with T1-4 brown microtomentose, T5 shiny.
Morphology. Head: frons with 2+0.5 orbital and 3 frontal setae, anterior frontal setae medioclinate. In males frons 2.3x as wide at posterior margin than at base of antenna, arista about 4.7x as long as basoflagellomere wide, pubescence on arista very short, posterior eye margin with notch (4-5oc) and narrow emargination (1oc).
Thorax: 2 dc, 1 prsc, 1 pprn, 1+0.3 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 converging (3.0), and ultimate section of vein M1 1.5-2x 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 setulose except on silvery parts, anterolateral corner with more than 3 lines of setae, T3-4 posterior margin setulose, T5 shiny parts setulose. S5 1.7x as long as wide, 1.8x as long and 1.1x as wide as S4, rectangular, posterior margin indented, setulose. Male genitalia with apical seta on cercus shorter than longest epandrial seta; pregonite with tuft of strong setulae and 0 setae on subepandrial plate, surstylus 0.3x as long as epandrium high, with anteroventral edge, slightly dilated posteroapically (1.3x), anterior margin slightly incurved, 1.6x as long as wide, structure of lateral surface striate, medial surface without setulae, some long sensilla at margin and one in middle.
Special characters: notch in posterior eye margin sometimes with sharper angle.
Body length: 2.9-3.0 mm; wing length: 2.7 mm.