Milichiella opuntiae has been reared from Opuntia (Platyopuntia) and Myrtillocactus (Cactaceae).
Differs from other members of the aethiops-group in the combination of 3-4 prsc and light brown calypter. Differs from M. pseudopuntiae in the stronger setulose postgena, mesonotum slightly brown microtomentose, and S5 stronger setulose and setulae longer.
Male coloration and vestiture: frons black, ocellar triangle slightly black microtomentose, orbital plates shiny black, lunule black, basoflagellomere black, face silvery grey microtomentose, palpus black; thorax with mesonotum slightly brown microtomentose, scutellum and pleura same except for shiny spot on an- and katepisternum, wing hyaline, veins brown, brown spot at tip of vein R1 absent, calypter hyaline with hyaline or light brown margin, halter black, legs black; abdomen with T2-5 black microtomentose except for shiny posterolateral margins of T2-4 and posterior 3/4 of T5. Female coloration and vestiture: halter yellow, abdomen with T1-4 brown microtomentose dorsally, T5 shiny.
Morphology. Head: frons with 2 orbital and 3 frontal setae, middle frontal seta medioreclinate. In males frons 1.2x as wide at posterior margin than at base of antenna, arista about 3.7x as long as basoflagellomere wide, pubescence on arista very short, posterior eye margin without notch, gradually separating from head margin ventrally.
Thorax: 4+1 dc, 4+1 prsc, 1 pprn, 2 prs and row of short setae, 1 strong and 2+0.8 thinner 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 (1.9), and ultimate section of vein M1 1.7x as long as penultimate section. Fore femur strongly setulose, tibial organ absent.
Male abdomen: posteromedial triangular projection of T1 into T2 weak. Tergal chaetotaxy: T2 anterolateral corner with more than 3 lines of setae, T2-5 setulose. S5 about as long as wide, about 1.3x as long and 1.1x as wide as S4, roughly quadrangular; posterior 2/3 setulose. Male genitalia with apical seta on cercus shorter than longest epandrial seta, 1 seta on subepandrial plate, surstylus as long as epandrium high, slightly bent posteriorly and dilated apically (1.4x) bent anteriorly, about 6.2x as long as wide, structure of lateral surface smooth, medial surface without setulae.
Special characters: mesonotal setulae scarce, setae long, setae on lunule longer than interfrontal setulae.
Body length: 3.2 mm; wing length: 3.0 mm.