EN
The adult and deutonymph oi Microtrombidium pusillum (Hermann, 1804) are redescribed; the heteromorphic larva reared in laboratory is described for the first time. The taxonomic status of the genus is revised; diagnoses of all active instars are provided. The neotype is designated basing on the female from which larvae have been obtained by experimental rearing. Megophthrombium Mullen and Vercammen-Grandjean, 1978, Phlebotrombium Fain and Baker, 1993 and Crinitrombium Southcott, 1994 are considered subjective junior synonyms of Microtrombidium Haller, 1882. Larvae hitherto described as Microtrombidium do not belong to this genus; their generic status is discussed. Alexothrombium gen. nov. based on Microtrombidium baerti Fain and Grootaert, 1993 as type species and Parawillungella gen. nov. based on Microtrombidium nitidum Southcott, 1994 as type species are described. The phenology, life cycle and parasitism of M. pusillum are discussed and compared with adequate data for other Microtrombidiidae.