Differs from M. nudiventris in male abdomen with T2 brown microtomentose except for silvery lateral sides, T3-5 silvery microtomentose except for brown microtomentose posteromedial margin of T3 and subshiny tip of T5.
Male coloration and vestiture: frons brown, ocellar triangle and orbital plates brown microtomentose, lunule brown, basoflagellomere black, face greyish microtomentose, palpus black; thorax with mesonotum densely brown microtomentose, scutellum and pleura same except for small shiny spots on an- and katepisternum, wing hyaline, veins brown, brown spot at tip of vein R1 absent, calypter brown, halter black, legs black except for yellow basitarsi, fore and hind tarsus with yellow brush; abdomen with T2 brown microtomentose except for silvery lateral sides, T3-5 silvery microtomentose except for brown microtomentose posteromedial margin of T3 and subshiny tip of T5. Female coloration and vestiture: halter black, abdomen with T2-5 brown microtomentose.
Morphology. Head: frons with 2+0.5 orbital and 2 frontal setae, anterior frontal seta very slightly medioreclinate. In males frons 2.2x as wide at posterior margin than at base of antenna, arista about 5.0x as long as basoflagellomere wide, pubescence on arista short, about as long as base of arista wide, posterior eye margin with slight notch (4oc) and emargination (3oc). Female posterior eye margin with slight notch (4oc) and emargination (2oc).
Thorax: 2 dc, 2 prsc, 1 pprn, 1 prs, 1+0.7 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 weakly converging (1.5), and ultimate section of vein M1 2.3x as long as penultimate section. Fore femur normal setulose, tibial organ absent.
Male abdomen: posteromedial triangular projection of T1 into T2 very weak. Tergal chaetotaxy: T2 anterolateral corner with 2-3 lines of setae, T2-5 bare except for setulose tip of T5. S5 1.5x as long as wide, 1.3x as long and 4.6x as wide as S4, roughly triangular with posterior margin indented, scarce setulose except for strong setulose at posterior margin. Male genitalia with apical seta on cercus longer than epandrial setae, 1 seta on subepandrial plate, surstylus 0.7x as long as epandrium high, bent posteriorly, dilated apically (2.1x), 5.3x as long as wide, structure of lateral surface smooth, medial surface with two fine setulae at posterior margin.
Special characters: silvery microtomentum long.
Body length: 2.8-3.4 mm; wing length: 2.4-2.9 mm.
Milichiella turrialba belongs to the nudiventris-group. It is possible that M. turrialbae is just a variety of M. nudiventris because it differs only in the partly brown microtomentose male T2-3.