Lathrobium volkeri, Senda, 2024

Senda, Yoshihiro, 2024, Seven new species of the genus Lathrobium Gravenhorst (Coleoptera: Staphylinidae: Paederinae) from Central Honshu, Japan, with new distributional records, Zootaxa 5403 (5), pp. 501-529 : 517-520

Lathrobium volkeri sp. nov.

( Figs. 1G , 10 , 12 )

http://zoobank.org/ urn:lsid:zoobank.org:act:C6794E76-ABED-453A-B946-0D556AC62C5F

Type material. Holotype: JAPAN: Honshu: ♂, “ Sanage-yama | Aichi Pref. | 24.X.1970 | K. Yamagishi leg.” [handwritten on white label], “HOLOTYPE | Lathrobium volkeri sp. nov. | Des. Y. Senda, 2022 ” [printed on red label with black border]. (EUMJ). Paratypes: 3♂♂, 6♀♀, Mt. Sanage-yama, Sanage-chô, Toyota-shi , 35.1962°N, 137.1711°E, alt. 461 m, 21.XII.2022, T. Ôno leg., NIAES-STAPH-JPN560, 561 (pcYS, NARO) .

Diagnosis. The new species is superficially similar to Lathrobium brachypterum Sharp, 1889 but distinguishable from it by the following characteristics: 1) male abdominal sternite VIII weakly emarginated at middle of posterior margin; 2) aedeagal ventral process comparatively wide in apical half; 3) dorsal plate of aedeagus with small dorsal projection at apical 1/3 and small hook at apex (while in L. brachypterum : male abdominal sternite VIII subtruncated at middle of posterior margin; ventral process comparatively slender in apical half; dorsal plate of aedeagus with small dorsal projection at apical 1/4 and acute apex). The new species is also resembles Lathrobium satoi Watanabe, 2003 , but is different from the latter by the following characteristics: 1) aedeagal ventral process weakly curved to right in apical half; 2) dorsal plate of aedeagus comparatively long, with small dorsal projection at apical 1/3 and small hook at apex (while in L. satoi : aedeagal ventral process distinctly curved to right in apical half; dorsal plate of aedeagus comparatively short, with small hook at the apex).

Description. Colouration: Body dark reddish brown to black; antennae, mandibles, labrum, basisternum, meso- and metavantrite reddish brown; labial palpi, maxillae, legs and abdominal segment IX (apical part) and X brownish yellow; elytra usually dark reddish brown in sutural and apical area.

Male. Body elongate, subparallel-sided, slightly flattened dorsally, shining. Head subhexagon in dorsal view, lateral sides gently arcuate, widest at basal 1/3 of posterior part of eyes, HL/HW ≈ 1.0; surface with coarse setiferous punctures and coriaceous microsculpture; punctures of surface becoming denser and less coarse in temporal area. Eyes small, about 0.3 times as long as temple, flat.Antennae moderate in length, AL/FBL ≈ 0.6; antennomere I widest at about apical half, dilated to widest point, thence feebly contracted toward apex; antennomere II constricted at the base; III–X almost moniliform; antennomere XI fusiform, pointed at apex; length/width ratio of each antennomere I to XI as follows: 2.5, 1.7, 1.4, 1.3, 1.4, 1.4, 1.4, 1.4, 1.4, 1.4, 2.1; relative lengths of antennomeres from base to apex: 23.5: 12.5: 11.5: 11.0: 10.3: 10.3: 10.3: 10.3: 10.0: 10.0: 13.8, and relative widths: 14.6: 11.5: 12.3: 13.1: 11.5: 11.5: 11. 5: 11. 5: 11.2: 11.2: 10.0.

Pronotum oblong, widest at anterior 1/5, PL/PW ≈ 1.2, PL/HL ≈ 1.4, PW/HW ≈ 1.2, lateral sides feebly arcuate, contracted from widest point to posterior corner; disc sparsely covered with coarse and setiferous shallow punctures except median smooth area; anterior margin very feebly emarginate at middle, broadly rounded at corners; posterior margin almost straight, rounded at corners. Scutellar shield impunctate, covered with indistinct microsculpture, sparsely covered with fine brownish pubescence. Elytra widest just before posterior corner, expanded weak arcuately from base to posterior corner, EL/EW ≈ 0.7, EL/PL ≈ 0.6, EW/PW ≈ 1.1; disc covered with shallow punctures, sparsely covered with fine brownish pubescence. Hind wings absent. Legs rather slender, covered with golden pubescence; protarsomeres I–IV strongly dilated.

Abdomen covered with minute punctures, densely covered with dark brownish pubescence; sternite VI ( Fig. 10A ) without median depression; sternite VII ( Fig. 10A ) without median depression, but covered with short black setae in the posteromedial area, not emarginate at posterior margin; tergum VIII feebly arcuate at posterior margin; sternite VIII ( Fig. 10A ) with triangular median depression, which is covered with short black setae, with posterior margin weakly emarginated at middle; tergum IX setigerous except on basal 1/4, with posterolateral projections as long as 1/4 of tergum IX and slightly curved dorsally from apical 1/3 to pointed apex; sternite IX elongate, widest at basal 1/4, narrowed apically, setigerous in 2/3, with posterior margin feebly arcuate; tergum X trapezoidal, widest at basal corners, with few setae and pores, with posterior margin arcuate.

Aedeagus ( Fig. 10B–D ) robust, 1.83 mm long, well sclerotised except membranous dorsal side; dorsal plate elongate and slender, symmetric, widest at apical 1/3, weakly curved ventrally at apical 1/3, gently dilated emarginately to widest point, thence emarginately contracted toward acute apex in dorsal view, with small dorsal projection at apical 1/3 and small hook at the apex; ventral process slightly asymmetrical, strongly curved ventrally at apical half, weakly curved to right in apical half, almost parallel-sided in basal 1/3, thence strongly contracted toward acute apex in ventral view, with fine longitudinal carina along midline in apical 1/3. Endophallus ( Fig. 10 E–F ): slightly longer than dorsal plate, simple, symmetric, without any membranous projection in everted condition, with ventrolateral teeth patch as Fig. 10E–F ; sclerotised copulatory piece lacking, but with numerous minute sclerites on dorsal side of apex.

Female. Similar to male in general appearance. Length/width ratio of each antennomere I to XI as follows: 2.9, 1.2, 1.4, 1.3, 1.3, 1.3, 1.3, 1.2, 1.3, 1.3, 2.4; relative lengths of antennomeres from base to apex: 26.7: 10.0: 11.7: 10.8: 10.8: 10.8: 10.8: 10.0: 10.0: 10.0: 15.8, and relative widths: 13.8: 12.5: 12.5: 12.5: 12.5: 12.5: 12.5: 12.5: 11.3: 11.3: 10.0. HL/HW ≈ 1.0; AL/FBL ≈ 0.6; PL/PW ≈ 1.2; PL/HL ≈ 1.3; PW/HW ≈ 1.1; EL/EW ≈ 0.8; EL/PL ≈ 0.7; EW/PW ≈ 1.1.

Tergum VIII ( Fig. 10G ) weakly project at middle of posterior margin; sternite VIII ( Fig. 10H ) subtruncate at middle of arcuate posterior margin; tergum IX ( Fig. 10G ) similar to male, with thicker posterolateral projections and large subtriangular flap-like ventral plate on the base; tergum X ( Fig. 10G ) similar to male. Gonocoxites ( Fig. 10H ): lateral gonocoxal plate (distal and proximal gonocoxites fused) elongate, setigerous, with a few setae in apical area, with asymmetrically rounded apex.

Measurements. Male (n = 3)—BL: 7.68–7.83 mm (7.77± 0.08 mm); FBL: 3.12–3.32 mm (3.23± 0.10 mm); HL: 0.93–1.01 mm (0.97± 0.04 mm); HW: 0.97–1.06 mm (1.00± 0.05 mm); AL: 1.81–1.88 mm (1.86± 0.04 mm); PL: 1.34–1.41 mm (1.37± 0.04 mm); PW: 1.11–1.19 mm (1.15± 0.04 mm); EL: 0.84–0.94 mm (0.89± 0.05 mm); EW: 1.19–1.23 mm (1.22± 0.02 mm).

Female (n = 5)—BL: 7.47–7.84 mm (7.71± 0.15 mm); FBL: 3.11–3.28 mm (3.20± 0.07 mm); HL: 0.92–1.01 mm (0.96± 0.03 mm); HW: 0.92–0.99 mm (0.96± 0.02 mm); AL: 1.80–1.82 mm (1.81± 0.01 mm); PL: 1.25–1.32 mm (1.28± 0.03 mm); PW: 1.01–1.10 mm (1.06± 0.03 mm); EL: 0.91–0.99 mm (0.95± 0.04 mm); EW: 1.12–1.18 mm (1.15± 0.03 mm).

Distribution. Japan: Central Honshu (northwestern area of Aichi Prefecture) ( Fig. 12 ).

Etymology. The specific name is dedicated to late Dr Volker Assing (Hannover), whose lifelong contributions to the taxonomy of Palaearctic and Oriental staphylinid beetles have been invaluable. Furthermore, this paper was started in collaboration with him.

Comments. This new species is unequivocally classified in the Lathrobium brachypterum group (sensu Senda, 2023b) based on its characteristic states.

Figures

FIGURE 1. Holotypes of Lathrobium spp., dorsal habitus: L. oopikkarianum sp. nov. (A); L. elongatiphallus sp. nov. (B); L. tomohidei sp. nov. (C); L. pegaseion sp. nov. (D); L. minoccidentale sp. nov. (E); L. kawamurai sp. nov. (F); L. volkeri sp. nov. (G). Scale bars = 1.0 mm.

FIGURE 10. Lathrobium volkeri sp. nov., male (A–F) and female (G–H): apical part of abdominal sternites (A, H); aedeagus, ventral view (B); ditto, lateral view (C); ditto, dorsal view (D); inverted endophallus of aedeagus, ventral view (E); ditto, lateral view (F); apical part of abdominal terga (G). Scale bars = 0.5 mm.

FIGURE 12. Geographical distribution of Lathrobium kawamurai sp. nov., L. volkeri sp. nov., L. satoi Watanabe and their related congeners in central Honshu, Japan.