| abstract | Descriptions of two new oribatid mite species found in the park zone of the city of Yuzhno-Sakhalinsk, Sakhalin Island, Russia are provided. Xenillus similis sp. n. is a large light brown species in which the lamellae cover most of the proterosoma, the cusps are large, separate, knife-shaped with sharpened, diverging, medial teeth. The translamella is narrow with a tiny tooth between the cusps. The sensilla are fusiform. The new species is distinguished from the apparently most similar species X. sculptrus Kulijev 1963 by the thinner rostral and lamellar setae, the longer interlamellar setae and sensilla, the different shapes of the sensilla (fusiform, vs. clavate), lamellae (in X. sculptrus they are broadened towards the anterior end) and cusps. The new species differs from X. tegeocranus (Hermann 1904) by the thin and poorly pubescent dorsal and ventral setae, the shorter lamellar setae, the longer and sparsely pubescent interlamellar setae, the fusiform sensilla (vs. clavate), and the shape of the cusps with more elongated internal teeth. Lasiobelba (Lasiobelba) sakhalinensis sp. n. is a middle-sized species in which the rostrum is slightly projected and rounded. Costulae are absent, prodorsal setae smooth, the sensilla fusiform without a spire on top. Ten pairs of notogastral setae are long and smooth (except for setae c which are represented by alveoli), p1–p3 are shorter than the others. The anogenital setae are thin and smooth. The discidium is sharpened. Leg claws are thin. From the likewise morphologically similar L. (L.) remota Aoki 1959 and L. (L.) insulata Ohkubo 2001 the new species differs by the smaller size and fusiform sensilla without a spire on top (vs. both L. (L.) remota and L. (L.) insulata have long sensilla widened in the middle part with a spire on top), the shorter interlamellar setae (vs. they almost reach the insertion points of lamellar setae), and the smooth prodorsal and notogastral setae. |