Mirabilithrombium turcicum sp. nov. is described based on both active postlarval forms and larvae. Larvae of Mirabilithrombium Gabrys, 1999 were obtained by experimental rearing from a field-collected female and are described for the first time. This is the third species described in the genus; a key to the active postlarval forms is provided. Data on the habitat specificity for the species are provided.