Lathrobium (Lathrobium) aevenum Ryabukhin, 2017

Ryabukhin, A. S., 2017, A New Species Of The Genus Lathrobium Gravenhorst (Coleoptera: Staphylinidae, Paederinae) From Magadan Region, Far Eastern Entomologist 335, pp. 20-24 : 20-23

Lathrobium (Lathrobium) aevenum Ryabukhin , sp. n.

Figs 1–7

TYPE MATERIAL. Holotype – ♂, Russia: Magadan Region, environs of Evensk village, 26.VII 2007 (A.S. Ryabukhin). Paratypes – the same locality as holotype, 9–29.VII 2007, 7 ♂, 8♀ (A.S. Ryabukhin).

DESCRIPTION. Head and pronotum reddish-brown to dark-brown. Elytra usually slightly darker, brown to dark-brown, sometimes to almost black. Sutural and apical margins a little bit lighter, reddish-brown to brown. Abdomen dark-brown to black, with apical segments sometimes more or less lightened. Antennae, mouthparts (except reddish-brown mandibles), and legs dark-yellow to yellowish-brown. Head, pronotum and elytra distinctly, abdomen moderately shining. Surface of head, pronotum and elytra with sparse, yellowish pubescence and a few scattered brownish setae, abdomen with moderately dense yellowish pubescence with golden shine. Length 3.8–4.3 mm, specimens with extended abdomen – 4.4 mm.

Head equal or a little bit broader across basal 1/4 than length from neck to anterior margin of clypeus (45:44). Basal angles broadly rounded; basal margin slightly sinuate or almost straight. Temples slightly convex, approximately 3.6 times longer than eyes (ratio on average 25: 7); gradually widens posteriad (ratio of width at level of eyes at their posterior margins to maximum width on average 42: 45). Punctation deep and moderately dense, irregular, sparser medially. Distance between punctures on average 1-3 times as wide as diameter of punctures. Punctation of temples irregular, considerably weaker than that of disk, but quite evident. Surface with fine and distinct cellular or reticular microsculpture, welldeveloped throughout. Antennae moderately long, reaching the basal third of pronotum. Length/width proportions of 1-11 antennal segments as 15/6.5; 7/5,5; 6.5/6; 6/6; 6/6; 6/6; 6.5/6; 6.5/6; 7/6; 7/6.5; 11/6.5.

Pronotum moderately convex, a little bit narrower than head (44: 45), approximately 1.2 times longer than width (ratio on average 54: 44). Lateral sides parallel, sometimes very slightly narrowed to base. Anterior and posterior angles broadly rounded. Apical and basal margins straight or very slightly sinuate. Median longitudinal impunctate strip reaching apical and basal margins, not raised above surface of pronotum. Ratio between its width to width of pronotum on average as 10: 44. Median longitudinal furrow in basal half not reaches basal margin. Punctation irregular, variable, on average about equal to that of discal part of head. Punctures near the smooth longitudinal median strip forming more or less regular longitudinal rows. Surface with extremely fine, irregular, hatched or linear microsculpture, almost vanishing on median part of disc.

Elytra flattened, approximately 1.3 times shorter than pronotum (ratio on average 42: 54); conjointly on average 1.2 times broader than length (50: 42), distinctly shorter at sutural margin, than at lateral one (31: 42). Apical margin obliquely truncate. Sides straight, gradually and evenly widened from rounded humeral angles to apex (ratio of width at humeral level to maximum width on average 40: 50). Outer apical angles broadly rounded. Suture slightly but distinctly raised. Broad and shallow indistinct impressions along each side of suture extending to base and almost to apex of elytra. Punctation irregular, much more indistinct than that of head and pronotum. Diameter evidently less than those on pronotum. Surface with fine but distinct irregular hatched or shagreen microsculpture. Wings absent.

Abdomen evenly and weakly widened posteriad. Segments 6 and 7 slightly broader than others. Apical margin of tergite 7 without light fringe. Punctation fine, shallow, moderately dense, sparser in median parts of tergites. Diameter of punctures evidently less than that on elytra. Surface with well-developed, moderately dense, reticulate or reticulate-waved microsculpture.

MALE. Aedeagus asymmetrical, internal sac with ring-shaped structure. Lateral and ventral views as in Figs 1-2 respectively. Abdominal sternite 8 with a more or less developed shallow, oval-shaped apico-median impression. Posterior margin with slightly asymmetrical, rather broad and deep angularly rounded emargination as in Fig. 3 .

FEMALE. Dorsal and ventral views of genital segment as in Figs 4 and 5 respectively. Abdominal tergite 8 as in Fig. 6 . Sternite 8 as in Fig. 7 . DISTRIBUTION. Russia: Magadan Region. ETYMOLOGY. The specific name is derived from the village name Evensk , near which the holotype and paratypes were collected .

DIAGNOSIS. Lathrobium aevenum sp. n. is similar to L. transsibiricum Ryvkin, 1989 from Magadan Region (Ryvkin, 1989), L. temporaneum Ryvkin, 2007 from Khabarovsk Region (Ryvkin, 2007) and (Ryabukhin, 2015).

L. palanum Ryabukhin, 2015 from Kamchatka From L. transsibiricum new species differs by the smaller body size, by narrower head, by widened temples, by longer antennae and by shorter pronotum. L. aevenum sp. n. can be distinguished from L. temporaneum by the rather smaller body size, by the darker colour, by broader head, by shorter temples, by less narrow pronotum and by evidently broader elytra. From L. palanum new species differs by the darker elytra and abdomen, by shorter temples and by the broader elytra. New species can be distinguished from all other species of the genus Lathrobium by the shape of aedeagus.

REMARKS. The specimens of Lathrobium aevenum sp. n. have been collected by sifting and hand picking ground cover and litter in the grass-dwarf shrub tundra under the clumps of the dwarf birch ( Betula exilis ).

Figures

Figs. 1–7. Lathrobium (Lathrobium) aevenum sp. n. 1, 2 – aedeagus: 1 – lateral view; 2 – ventral view; 3–8 – details of structure of abdominal segments without pubescence: 3 – male 8th sternite, ventral view; 4 – female genital segment, dorsal view; 5 – the same, ventral view; 6 – female 8th tergite, dorsal view; 7 – female 8th sternite, ventral view.