The four species of the genus Diolcogaster Ashmead, 1900, present in Iran are reviewed. Field sampling was done during 2010 to 2016 in eastern and southeastern parts of Iran by various methods. The identity and morphological variability of D. alvearia (Fabricius), D. claritibia (Papp), D. mayae (Shestakov) and D. spreta (Marshall) were compared with other Palaearctic material. Three species, D. claritibia, D. mayae and D. alvearia, are illustrated and redescribed and the intraspecific variation of D. mayae is presented for the first time. Examination of the additional specimens revealed eleven new records: D. alvearia (Croatia), D. claritibia (Tunisia and Ukraine), D. mayae (Algeria, Israel, Russia and Yemen) and D. spreta (Bulgaria, Denmark, Germany and Spain). A key to the species found in Iran, as well as information about their distribution, are also provided.
Keywords: Diolcogaster, Lepidoptera, key, intraspecific variation, distribution, Iran, Hymenoptera.