| abstract | Oplitis Berlese is the largest genus of the mite family Oplitidae (Mesostigmata), with a worldwide distribution. A new oplitid mite Oplitis quadrigenitalis Babaeian sp. nov. is described and illustrated, based on adult females collected in the nest of Lasius neglectus (Hymenoptera: Formicidae) in Taleghan region (Alborz Province), Iran. Within this genus, the new species is unique with regard to the combination of the following character states: (1) dorsal and most ventral idiosomal setae obovate-mucronate, (2) sternal region free, only fused with ventral shield posterolaterally, (3) epigynal shield square-shape and finely punctated, (4) perigenital ring undulating and entire in whole length, (5) peritreme U-shape, and (6) epistome with denticulate base and numerous outgrowths apically. |