Milichiella sumptuosa was collected swarming on bugs, in front of cowsheds and under trees in sun, collected over and along creeks in forest and at “lcol.-light”.
Differs from congeners in the combination of posteriorly silvery microtomentose mesonotum, silvery T2-5 and strongly setulose posterolateral corners of S5.
Male coloration and vestiture: frons subshiny black, ocellar triangle and orbital plates brown microtomentose narrow frontal plates grey microtomentose, lunule brown, basoflagellomere black, face brown or greyish microtomentose, palpus black; thorax with mesonotum anteriorly brown microtomentose, posteriorly silvery (var.: completely brown); scutellum and pleura brown microtomentose, wing hyaline, veins yellow, brown spot at tip of vein R1 absent, calypter brown or yellow with brown margin, halter black, legs black except for yellow basitarsi; abdomen with T2-5 silvery microtomentose. Female coloration and vestiture: frons subshiny black, ocellar triangle and orbital plates brown microtomentose, wide frontal plates silvery grey microtomentose, thorax with mesonotum greyish to yellowish brown microtomentose, median line and scutellum more brownish, lateral sides more greyish, pleura same except for shiny spots, calypter hyaline with yellow margin, halter yellow, abdomen with T2-5 brown microtomentose.
Morphology. Head: frons with 2 orbital and 2 frontal setae, anterior frontal seta medioclinate. In males frons 2.1-2.6x 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 (5-6oc) and emargination (male: 1oc, female 3oc).
Thorax: 2-5 (female: 2) dc, 2 (female: 1) prsc, 1 pprn, 1 prs and row of 0.5 setae (female:1 prs), 2+0.6 keps setae, posterior prsc about as long as posterior dc, seta between posterior prsc and posterior dc present. Wing with vein R4+5 and M1 converging (2.2), and ultimate section of vein M1 2.2-2.4x as long as penultimate section. Fore femur strongly setulose, tibial organ absent.
Male abdomen: posteromedial triangular projection of T1 into T2 present. Tergal chaetotaxy: T2 anterolateral corner with 2-3 lines of setae, T2 posterior margin with 2 rows of scarce setulae, T3-5 with one row of setulae. S5 1.6x as long as wide, 2.1x as long and 1.9x as wide as S4, strongly setulose with long setae at posterolateral corners. Male genitalia with apical seta on cercus longer than epandrial setae; hypandrium long, 1 seta on subepandrial plate, surstylus 1.3x as long as epandrium high, bent posteriorly, dilated apically (1.7x), very narrow, 10x as long as wide, structure of lateral surface smooth, medial surface without setulae.
Body length: 2.4-3.2 mm; wing length: 2.7-3.0 mm.