Two new species of the bristletail genus Petrobiellus Silvestri, 1943 (Microcoryphia, Machilidae, Petrobiellinae) from the Russian far east

The small East Asian genus Petrobiellus Silvestri, 1943 has so far included three species: P. takunagae Silvestri, 1943 (Japan), P. sachalinensis Kaplin, 2020 (Sakhalin), and P. kusakini Kaplin, 1980 (Simushir Island, Kuril Islands). Two new species are added herewith: P. nematocerus sp. n. (Furugelm Island, Sea of Japan) and P. leleji sp. n. (Atlasov Island, Kuril Islands). Among them, the former new species seems to be particularly similar to P. sachalinensis, vs the latter new species which seems most similar to P. takunagae, the type species of the genus. Petrobiellus nematocerus sp. n. differs from P. sachalinensis in the color of the scales on the dorsal side of the body; the length ratio of the antennae to the body; the color of the paired ocelli and the distance between them relative to the total width of the compound eyes; the number of dentate setae on the dorsal side of the apical and pre-apical articles of the maxillary palps; the number of needle-shaped supporting setae on the 2nd article of the tarsi and tibiae; and the size of the apical angle of the abdominal sternites. Petrobiellus leleji sp. n. and P. takunagae differ in the distance between the paired ocelli relative to the total width of the eyes; the width to length ratio of the paired ocellus; the lengths of the last and penultimate articles of the maxillary palps, abdominal sternites and coxites, as well as the apical angle of the abdominal sternites and the number of articles in the parameres of the male.