Although the immature stages of oribatid mites of the family Ceratozetidae is well known compared to other families, information on the morphological ontogeny of most species is still insufficient or unknown. Comparative characteristics of immatures of species of the subfamily Trichoribatinae are given based on our own data and available literature sources. The major characteristics of immature instars of 20 species are presented. The ontogeny of only two species of Diapterobates is known, and here the morphology of ontogenetic instars of a third species, Diapterobates brevidentatus Bayartogtokh, 2010 is investigated. The larva and nymphs of this species are generally similar in their habitus. Basic characteristics of immatures are the body unpigmented, light yellowish or flesh-colored with porose cuticle; gastronotic and anogenital regions folded; humeral organ present; prodorsum stockier in larva than in nymphs and adult; gastronotic shield weakly sclerotized; prodorsal, gastronotic and ventral setae setiform, except clavate bothridial seta; larva with 12 pairs, nymphs with 15 pairs of gastronotic setae. Diapterobates brevidentatus is a Central and Southern Siberian species, currently known from central Russia (Yamal-Nenets Autonomous District) and northern Mongolia (Hövsgöl Province), and appears to be primarily an inhabitant of soil-litter of the mountain steppes and arboreal habitats of boreal coniferous forests.