Cosmolaelaps sejongi Keum, Jung and Joharchi, 2017: 487.
(Figures 45–49)
Specimens examined. Six females, Sakhalin Island, Russia, 46°44'06"N 142°12'17.5"E, 11 August 2021, O. Joharchi coll., in the nest of Lasius umbratus (Nylander) (Hymenoptera: Formicidae) (in TUMZ).
Remarks. Cosmolaelaps sejongi was described from Republic of Korea (Keum et al., 2017). It has been found from soil around roots of an oak tree (Keum et al., 2017), and is now recorded in Russia for the first time, in the nest of L. umbratus. Our specimens agree well with the description given by Keum et al. (2017). The species is easily recognised by the distinctive shape of the post-anal seta (thickened, sparsely barbed and apically hook shaped), which is inserted on a small tubercle (Figs 46, 49); dorsal shield setae thick and long, most setae long enough to reach well past the base of next posterior seta, and Z5 sparsely barbed, longer and thicker than J5 (Figs 45, 47); sternal setae short, not reaching base of following setae (Figs 46, 48); soft opisthogastric cuticle bearing 16 pairs setae, Jv5 well thickened, apically hook shaped and subequal in length with post-anal seta (Figs 46, 49).