The trombidiid subfamily Neotrombidiinae Feider is re-established and redefined, based primarily on larval characters but also on adult characters. It is closely related to the trombidiid Trombellinae on the one hand and to the Leeuwenhoekidae on the other. It consists of two genera, namely Monunguis Wharton, which is monobasic and known only from the larva, and Neotrombidium Leonardi, with 13 described species of which 7 are known from the larva and 8 from the adult (the larva and adult of 2 species are correlated by rearings).The history of the family-level placement of this group, and the controversy over whether or not to recognize two genera, are reviewed. The characters that justify the separate recognition of Monunguis and Neotrombidium are enumerated.The larva of each of the following species of Neotrombidiinae is described, illustrated and keyed: Monunguis streblida Wharton from the Caribbean area, Neotrombidium barringunense Hirst from Australia, N. tricuspidum Borland from North America, N. tenuipes (Womersley) from Malaya, N. samsinaki (Daniel) new combination from central Europe, N. anuroporum new species from Central America, N. bengalense new species from India, and N. tenebrione new species from eastern North America. Six other species of this group, known only from the adult, are listed separately but are not treated taxonomically here.The larvae of Neotrombidiinae parasitize adult insects: those of Monunguis are hyperparasites on streblid flies whereas those of Neotrombidium are ectoparasites of cerambycid, clerid, elaterid, and tenebrionid beetles that pass part of their life history under the bark of trees.In the Microtrombidiinae, Camerotrombidium Thor is noted as the valid replacement name for the preoccupied Ottonia Kramer.