Lasinus Sharp

Bekchiev, Rostislav, Hlavac, Peter & Nomura, Shuhei, 2013, A taxonomic revision of Tyrini of the Oriental region. V. Revision of the genus Lasinus Sharp, 1874 (Coleoptera, Staphylinidae, Pselaphinae), ZooKeys 340, pp. 21-42 : 22-23

Genus Lasinus Sharp

Lasinus Sharp, 1874: 106. Type species: Lasinus spinosus Sharp, 1874 (original designation, gender masculine).

Lasinus Sharp: Jeannel 1958: 121.

Lasinus Sharp: Hlaváč 2003: 286 (redescription).

Diagnosis.

The genus Lasinus can be readily separated from the other genera of the Pselaphodes complex ( Hlaváč 2003) by a combination of the following characters: 1) head with well-defined setose frontal and vertexal foveae, 2) maxillary palpi small, with palpomeres III–IV symmetrical, neither roundly expanded nor projecting laterally, 3) antennal club three-segmented, with antennomeres VIII–IX often modified in males, 4) pronotal lateral and median foveae well-defined, 5) pronotum lacking antebasal sulcus connecting foveae, 6) pronotal longitudinal sulcus present, well- to weakly-defined, 7) tarsal segments II linear, segments III inserted at the apex of the II, 8) basal carinae on the first visible tergite (IV) present, short, 9) median setose metaventral fovea absent, 10) metaventral horny processes reduced to short, stout protuberances.

Redescription.

Length 2.5-3.8 mm. Head lacking dorsally visible postgenae, with well-defined setose frontal and vertexal foveae, maxillary palpi small, symmetric. Antennae with scapes distinctly longer than pedicels, club three-segmented, antennomeres VIII–IX often modified in males, species characteristic. Pronotum with well-defined median and lateral foveae, longitudinal sulcus sometimes weakly-defined but always present, antebasal transverse sulcus absent. Elytra with two basal foveae and two striae, lacking carinae, punctate, covered by short, golden pubescence. Metaventrite with two stout, short protuberances instead of long horn-like processes, metaventral apex sharp, with shallow excavation, surface punctate and pubescent, median metaventral fovea absent. Legs long and slender, roughly punctate and pubescent, protrochanters, mesotrochanters, profemora and mesofemora with spines of various shape and length, metatrochanters and metafemora lacking spines, tarsomeres II linear, tarsomeres III inserted at the apex of II.

Sexual dimorphism.

Females of all species bear on mesotrochanters one or two more spines than males, females antennomeres VII–IX simple, without modification.

Relationship.

Due to the simple second tarsal segments and the absence of the median metaventral foveae, Lasinus is most closely related to the genera Paralasinus Hlaváč & Nomura, 2001, Pselaphodes Westwood, 1870 and Dayao Yin, Li & Zhao, 2011. From the latter two genera Lasinus can be separated by the completely symmetric palpomeres II–IV. In Pselaphodes and Dayao , the maxillary palpi have at least some palpomeres II–IV asymmetric, roundly expanded, or slightly to distinctly projecting laterally. Lasinus differs from Paralasinus by the pronotum lacking an antebasal sulcus, which is present in Paralasinus .

Habitat.

Members of the genus are usually collected by sifting leaf-litter in forested areas.

Distribution. China, Vietnam, Japan, Russia (Kuril Islands).

Key to species of Lasinus