Lathrobium pegaseion, 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 : 509-511

Lathrobium pegaseion sp. nov.

( Figs. 1D , 5 , 6 )

http://zoobank.org/ urn:lsid:zoobank.org:act:0AEC0AA2-F3C4-4116-9DFC-8A1577C1160F

Lathrobium sp. Senda, 2020: 188.

Type material. Holotype: JAPAN: Honshu: ♂, “JAPAN: Nagano-ken, | Nagano-shi, Togakushi , | Koshimizugahara , 1240m, | 3 VI 2018, S. Sejima, | 36.7499N, 138.0560E ” [printed on white label], “ Nø 県戸隠越水ヶ原, | Litter in woods mainly | composed of | Quercus crispula & | Larix kaempferi ” [printed on white label], “HOLOTYPE | Lathrobium pegaseion | sp. nov. | Des. Y. Senda, 2023” [printed on red label with black border]. (EUMJ). Paratypes : 2♂♂, 2♀♀, same data as holotype (EUMJ, pcYS) ; 1 ♂, 1 ♀, ditto, except Suginosawa, Myôkô-shi, Niigata, 36°51.7’N 138°08.2’E (pcYS) .

Diagnosis. The new species resembles Lathrobium loebli Assing, 2013 , but is different from the latter by the following characteristics: 1) posterior excision of male abdominal sternite VIII rather deep and triangular; 2) aedeagal ventral process comparatively narrow and distinctly asymmetry (while in L. loebli : posterior excision of male abdominal sternite VIII comparatively shallow and semicircular; aedeagal ventral process moderately wide and slightly asymmetry).

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

Male. Body elongate, subparallel-sided, slightly flattened dorsally, shining. Head subtrapezoid in dorsal view, lateral sides gently arcuate, widest at the half of posterior part of eyes, HL/HW ≈ 0.9; 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 1/3, dilated to widest point, thence gently 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: 2.2, 1.7, 1.7, 1.3, 1.4, 1.3, 1.3, 1.3, 1.3, 1.3, 1.8; relative lengths of antennomeres from base to apex: 26.2: 13.4: 13.4: 10.4: 10.4: 10.0: 10.0: 10.0: 10.0: 10.0: 14.2, and relative widths: 15.9: 10.5: 10.5: 10.5: 10.0: 10.5: 10.5: 10.5: 10.5: 10.5: 10.5.

Pronotum oblong, widest at anterior 1/4, PL/PW ≈ 1.2, PL/HL ≈ 1.3, PW/HW ≈ 1.0, lateral sides arcuately 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, rounded at corners; posterior margin almost straight, broadly rounded at corners. Scutellar shield impunctate, covered with indistinct microsculpture, sparsely covered with fine brownish pubescence. Elytra widest just before posterior corner, weakly expanded arcuately from base to posterior corner, EL/EW ≈ 0.7, EL/PL ≈ 0.6, EW/PW ≈ 1.0; 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. 5A ) with very weak median depression, sparsely covered with short black setae; sternite VII ( Fig. 5A ) with subtriangular median depression, which is sparsely covered with short black setae, weakly emarginate at posterior margin; sternite VIII ( Fig. 5A ) with subtriangular median depression, sparsely covered with short black setae, with rather deep triangular posterior excision, lateral side of posterior excision not produced on posterior margin; tergum IX setigerous except on basal 1/4, with posterolateral projections as long as 1/5 of tergum IX and strongly curved dorsally from apical 1/3 to pointed apex; sternite IX elongate, widest at half, with lateral sides, with arcuate posterior margin feebly arcuate; tergum X subtrapezoidal, widest at basal corners, with several setae and pores, with posterior margin truncate.

Aedeagus ( Fig. 5B–D ) elongate, 2.03 mm long, sclerotised except membranous dorsal side; dorsal plate elongate, almost symmetric, widest at apical 2/5, curved ventrally, emarginately dilated to widest point, thence gently and arcuately contracted toward round apex in dorsal view; ventral process long, lamellate, asymmetrical, widest at half, emarginately dilated to the widest point, weakly twisted and rather curved ventrally in apical half, which is distinctly emarginated in the right side, with short apical projection, which is approximately 0.1 times as long as ventral process. Endophallus poorly developed, with simple internal sac, without teeth patch.

Female. Similar to male in general appearance. Length/width ratio of each antennomere I to XI as follows: 2.7, 1.4, 1.5, 1.3, 1.3, 1.3, 1.3, 1.3, 1.3, 1.2, 1.8; relative lengths of antennomeres from base to apex: 26.9: 11.5: 11.5: 10.0: 10.0: 10.0: 10.0: 10.0: 10.0: 10.0: 15.4, and relative widths: 13.0: 11.0: 10.0: 10.0: 10.0: 10.0: 10.0: 10.0: 10.0: 11.0: 11.0. HL/HW ≈ 0.9; AL/FBL ≈ 0.6; PL/PW ≈ 1.2; PL/HL ≈ 1.3; PW/HW ≈ 1.0; EL/EW ≈ 0.7; EL/PL ≈ 0.6; EW/PW ≈ 1.0.

Tergum VIII ( Fig. 5E ) feebly project at the middle of posterior margin; sternite VIII ( Fig. 5F ) produced at the middle of posterior margin, which is arcuate and fringed with micropubescence; tergum IX ( Fig. 5E & F ) similar to male, but with large subtriangular flap-like ventral plate on base; tergum X ( Fig. 5E ) similar to male. Gonocoxites ( Fig. 5F ): lateral gonocoxal plate (distal and proximal gonocoxites fused) elongate, setigerous, with a few setae in apical area, with rounded apex.

Measurements. Male (n = 3)—BL: 7.35–7.68 mm (7.52± 0.17 mm); FBL: 2.86–3.08 mm (2.98± 0.11 mm); HL: 0.95–0.99 mm (0.97± 0.02 mm); HW: 1.03–1.06 mm (1.05± 0.02 mm); AL: 1.81–2.15 mm (1.94± 0.19 mm); PL: 1.19–1.29 mm (1.25± 0.05 mm); PW: 0.99–1.06 mm (1.03± 0.04 mm); EL: 0.72–0.80 mm (0.76± 0.04 mm); EW: 1.06–1.11 mm (1.08± 0.03 mm).

Female (n = 3)—BL: 7.12–7.53 mm (7.38± 0.23 mm); FBL: 2.71–2.98 mm (2.88± 0.15 mm); HL: 0.84–0.99 mm (0.93± 0.08 mm); HW: 0.87–1.07 mm (0.99± 0.11 mm); AL: 1.76–1.99 mm (1.85± 0.13 mm); PL: 1.13–1.25 mm (1.21± 0.07 mm); PW: 0.98–1.01 mm (1.00± 0.02 mm); EL: 0.72–0.76 mm (0.74± 0.02 mm); EW: 1.02–1.05 mm (1.03± 0.02 mm).

Only individuals collected in the type locality were measured.

Distribution. Japan: Central Honshu (northern area of Nagano Prefecture and southern area of Niigata Prefecture) ( Fig. 6 ).

Etymology. The specific name alludes to Mr Shôma Sejima, who is a collector of the holotype of this species and an old friend of mine. His first name, “Shôma (Ẹ馬),” is derived from the Japanese word for “the flying horse”, evoking imagery of Pegasus.

Comments. This new species belongs to the Lathrobium pollens group (sensu Senda, 2022) based on its characteristic states. No significant morphological variations were observed between populations from different localities. According to the collector of the type specimens, they were collected by sifting leaf litter in a forest mainly composed of Quercus crispula Blume ( Fagales , Fagaceae ) and Larix kaempferi (Lambert) Carrière ( Pinales , Pinaceae ).

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

FIGURE 6. Geographical distribution of Lathrobium oopikkarianum sp. nov., L. elongatiphallus sp. nov., L. tomohidei sp. nov., L. pegaseion sp. nov. and their related congeners in central Honshu, Japan.