Lathrobium denchu, Sato & Maruyama, 2023

Sato, Yuya & Maruyama, Munetoshi, 2023, Taxonomy of the Lathrobium nomurai group (Coleoptera: Staphylinidae) from Northern Kyushu, Japan, with descriptions of two new species, Acta Entomologica Musei Nationalis Pragae (Acta. Ent. Mus. Natl. Pragae) 63 (1), pp. 111-124 : 119-121

Lathrobium denchu sp. nov.

[Japanese name: Kunisaki-ô-kobane-naga-hanekakushi]

( Figs 7 , 8 , 9 )

Type material. HOLOTYPE: 3, Japan : Kyushu, “ JAPAN:Oita-ken / Kunisaki-shi / Kunisaki-cho / Jôbutsu / 33.587414, 131.6092694 / 19. XI. 2022. / H. Tanaka ” ( KUM) . PARATYPES: 2 33, same data as holotype ( KUM).

Description. BL = 13.3–13.7 mm, FBL = 5.1–5.3 mm (n = 3). Coloration: Body ( Fig. 7A ) reddish brown or dark brown, moderately shining; maxillary palpi, light red; legs reddish brown but bases of tibia light black or darken; mandible and scutellum black or darken; elytra reddish brown but suture black; abdomen reddish brown, posterior margin of tergite VII and VIII light brownish red; tergite IX and X light yellowish red.

Head suborbicular, HL = 1.53–1.58 mm, HW = 1.50– 1.55 mm, HW/HL = 0.98, widest at the basal 1/3 of head; frontal area flattened; surface coarsely punctate; punctures sparser on frons and vertex, becoming denser toward posterior and lateral margins, with dark brown setae. Eyes small, slightly protruding; longitudinal diameter about 1/4 as long as temple in dorsal view. Antennae elongate, AL = 3.45–3.78 mm, AL/HL = 2.33, with whitish yellow setae; antennomere I robust, widest at apical 1/3; antennomere II slightly elongated, shorter than III; antennomeres III–X long, slightly narrow at base and widening towards apex, successively shorter and narrower toward apical antennomeres but IX and X almost same size; antennomere XI fusiform; relative length of antennomeres as follows: 1.83: 1.17: 1.25: 1.17: 1.13: 1.13: 1.13: 1.07: 1.00: 1.00: 1.30; relative maximum width of antennomeres as follows: 1.85:1.38: 1.31: 1.31: 1.23: 1.23: 1.23: 1.23: 1.23: 1.23: 1.00.

Pronotum elongate, with anterior margin wider than posterior one, PL = 1.90–1.95 mm, PW = 1.35–1.45 mm, PL/PW = 1.36, PL/HL = 1.24, PW/HW = 0.93, widest at apical 1/3; lateral sides of pronotum gently dilated to widest point, thence gradually convergent toward posterior margin; all corners obtusely rounded; disc sparsely covered with coarse and weak punctations except medial longitudinal line; punctures slightly sparser than on head, with brownish yellow setae.

Scutellum with sparse punctures. Elytra subtrapezoidal, widened posteriorly, EL = 1.02–1.13 mm, EW = 1.45–1.55 mm, EW/EL = 1.40, EL/PL = 0.56, EW/PW = 1.07; lateral margins almost straight; posterior corners rounded; disc covered with sparse and coarse punctations; punctations denser than on pronotum, with brownish yellow setae. Hind wing completely reduced. Legs with shortened tibiae and tarsi which are covered with golden setae; tarsomeres I–IV of protarsus dilated.

Abdomen elongate, gradually widened from segment III to V, thence contracted to the posterior end; each tergite covered with micropunctations and brownish yellow setae, distinctly long setae on each side near anterior margin; tergite X as long as posterolateral processes of tergite IX.

Male. SterniteVII ( Fig.7B ) transverse; median area of sternite VII with shorter and thicker setae than other areas; sternite VIII ( Fig. 7C ) square, with posteromedian impression; each side of posteromedian impression protruded weakly; median areaofsterniteVIIIwithshort-thicksetae; sterniteIXelongate.

Aedeagus ( Figs 8A–C ) 3.04 mm long, very elongate; ventral process well sclerotized, asymmetric in ventral view, straight in lateral view; apical part of ventral process very long and straight, almost same length as the basal and middle parts together; slightly curved toward left side in ventral view; basal and middle parts of ventral process ball-shaped, depressed like hollow in each lateral side at apical 1/ 4 in ventral view, thicker than apical part in lateral view; part above basal foramen transverse, with two projections at lateral side; surrounding of basal foramen sclerotized; dorsal plate sclerotized, widest at apical 1/4, gradually widened to the widest point at apical 1/4, thus contracted toward apex, with acute apex; internal sac large, with sclerotized and ringed part, twisted about 90 degrees at middle area; apical area of internal sac very flattened.

Female. Unknown.

Differential diagnosis. The new species is similar to Lathrobium katsumiae Y. Watanabe & Yoshida, 2007 , a member of the L. nomurai group described from Mt. Rokuro-yama and Ôkawara Kôgen, Tokushima Pref., in general appearance and aedeagal shape. However, the new species can be easily distinguished from it by the combination of the following characteristics: 1) possessing slenderer aedeagus; 2) apical part of ventral process curved left side in ventral view; 3) dorsal plate of aedeagus almost straight (in contrast, L. katsumiae has middle area of ventral process slightly extended toward lateral side, apical part of ventral process straight in ventral view, and dorsal plate of aedeagus curved dorsally at basal 1/3).

Etymology. The specific name of new species is dedicated to Mr. Hidekazu Tanaka who collected this species, using his nickname Denchu. Noun in apposition.

Biology. All specimens were collected from the under 10 cm of a heap of rock debris, at an altitude of about 150 m.

Distribution. Japan (Oita Pref., north of Kyushu).

Figures

Fig. 7. Lathrobium denchu sp. nov.A – habitus in dorsal view; B – male sternite VII; C – male sternite VIII. Scale bars = 2.0 mm for A, 0.5 mm for B, C.

Fig. 8. Male aedeagus of Lathrobium denchu sp. nov.A – ventral view; B – lateral view; C – dorsal view. Scale bar = 0.5 mm.

Fig. 9. Map showing the distribution of the Lathrobium nomurai group in Kyushu, Japan. Black rhombus – L. nomurai Nakane, 1955; black triangle – L. fujimotoi Y. Watanabe, 2001; black circle – L. hikosanense Y. Watanabe, 1998; black square – L. yufuense sp. nov.; black pentagon – L. denchu sp. nov.; A–G – localities of L. hikosanense: A – Mt. Daisen; B – Mt. Hiko-san (type locality for L. hikosanense); C – Hiraodai; D – Mt. Buccho-zan; E – Mt. Tachibana-yama; F – Mt. Iwara-yama; G – Kinsenji Temple.