Lasius vostochni

A L. vostochni sample from the southern Sikhote-Alin range was collected on a sandy river terrace within an area of dense woodland and a South Baikal collection was found under a stone in a Pinus steppe forest.

Identification
Seifert (2020) - Differs from its sibling species Lasius niger by a combination of more numerous metapleural setae, less numerous scape setae, less dense clypeal pubescence and a slightly longer terminal maxillary palp segment.

Distribution based on Regional Taxon Lists
Palaearctic Region: Russian Federation.

Nomenclature

 * . Lasius vostochni Seifert, 2020: 63, figs. 51-52 (w.) RUSSIA.

Worker
Absolute size rather small (CS 826 µm). Scape length index rather small (SL/CS900 0.961), maxillary palp length index comparably large (MP6/CS900 0.192). Eye large (EYE/CS900 0.252). Number of mandibular dents not recordable in the available material but most probably similar to situation in Lasius niger. Clypeal pubescence rather dense (sqPDCL900 3.92). Pronotal setae short (PnHL/ CS900 0.128). Setae number on dorsum of scape rather low (nSc900 6.1) but high on extensor profile of hind tibia and metapleuron below propodeal spiracle (nHT900 14.3, nSt900 8.0). Coloration: Head, gaster, petiole, coxae, femora and tibiae dark brown; mesosoma sometimes a little lighter; mandibles, scape, trochanter and tibiofemoral joint region pale yellowish-brown.

See table 6 in Seifert 2020 for additional morphometrics. The abbreviated names of various quantitative data shown above are defined here: Seifert 2020 Lasius characters.

Type Material
Holotype plus 4 paratype workers on the same pin labelled ”RUS: Ussuri: 42.97N, 133.52E, 160 m; Krivaya-Tal, Flussterrasse, Sandboden L. Kanter 1999.09.07-43a; 2 paratype workers labelled ”RUS: 51.3528°N, 106.4800°E Gusinoosersk-4W, 604 m Pinus steppe forest under stone I.Antonov 2009.07.11-145“; depository.

Etymology
Derived from the Russian word восточний, meaning ”eastern“ and referring to the geographic range that is east of the range of the sister species Lasius niger.