Tyrodes amamianus, Inoue & Nomura, 2023

Inoue, Shota & Nomura, Shûhei, 2023, New species and record of Tyrodes Raffray (Coleoptera: Staphylinidae: Pselaphinae) from Japan, Zootaxa 5375 (1), pp. 83-92 : 88-91

Tyrodes amamianus sp. nov.

( Figs 5 , 6D–F )

[Japanese common name: Amami-Nisekoke-arizukamushi]

Type material. HOLOTYPE: ♂, “ JAPAN: RYUKYUS / Is. Amami-oshima / Mt. Yuwandake / 2. IV. 1991 / T. Ueno leg. // FAUNA JAPONICA / Staphylinidae , Pselaphinae // Tyrodes sp. 2 // S. Nomura det., 2021”

Diagnosis. This species is easily distinguished from its congener by the elongate antennomeres 9–10, abdominal sternite IV with densely setose patch at posterolateral in concavity and endophallus composed of two sclerites which are long and basally twisted one and apically bifid one.

Description. Male ( Fig. 5 ). BL 1.92 mm. Dorsal surface with dense, moderately long setae.

Head slightly wider than long (HL/HW 0.87), HL 0.34 mm, HW 0.39 mm, with both antennal tubercles closely situated each other, forming short frontal rostrum; frontal rostrum narrow, about half as long as HL, 1/3 as wide as HW, with few punctures, with small, nude frontal fovea at middle; posterolateral clypeal region strongly concave, its edge demarcated, angularly projected laterally and visible in dorsal view; vertex finely punctate, with a pair of setose fovea; eyes large, prominent; postocular margin rounded, with tufts of dense setae. Antennae each long, 1.21 mm in length; antennomeres 1 each longer than wide, 0.12 mm in length, with triangular projection on external side of basal part ( Fig. 5C ); relative length of each antennomere to antennomeres 1 as follows: 1.0: 0.72: 0.72: 0.63: 0.63: 0.55: 0.55: 0.55: 1.28: 1.28: 2.28; antennomeres 2 each longer than wide; antennomeres 3 each slightly widened towards apex, with posterior part 2/3 as wide as anterior part; antennomeres 3–5 each longer than wide; antennomeres 6–8 each as long as wide; antennomeres 9–11 each enlarged to form club, longer than wide, length/width ratio of 9–11 as follows: 1.47: 1.36: 1.89; antennomeres 11 each largest, subconical, about twice times longer than wide. Maxillary palpi with palpomeres 2 each narrowed and pedunculate at basal half, gradually widened apicad; palpomeres 3 narrowed and pedunculate at basal third, gradually widened apicad; palpomeres 4 each narrowed and pedunculate at base, widened apically, widest at middle, then narrowed apically, with apical appendage.

Pronotum as long as wide (PL/PW 1.00), PL 0.42 mm, PW 0.42 mm, widest at apical third, with anterior margin shorter than posterior margin, finely punctate, with transverse antebasal sulcus connecting small median setose fovea and large lateral setose foveae. Elytra nearly trapezoidal, wider than long (EL/EW 0.73), EL 0.60 mm, EW 0.81 mm, longer than pronotum, finely punctate; each elytron with two basal setose foveae; discal stria each shallow, extend to elytral midpoint. Mesoventrite with setose median mesoventral foveae small, with lateral mesoventral foveae setose, with lateral mesocoxal foveae setose; metaventrite finely punctate, polished, with median metaventral foveae setose, with setose small projection at middle ( Fig. 5D ); posterior margin of metaventrite with looped notch. Legs with coxae lacking spines; with femora each broadest at middle; profemora each simple; protibiae and metatibiae each nearly straight; mesotibiae each weakly arcuate at apical third; tarsi each elongate, about half as long as each tibia, with metatarsi longest; tarsomeres 1 each very short; tarsomere 2 and 3 each elongate; 3 each slightly longer than 2, with symmetrical tarsal claws.

Abdomen wider than long (AL/AW 0.69), AL 0.57 mm, AW 0.82 mm, finely punctate, with tergite IV longer than V, with shallow basal sulcus; IV–VIII each with a pair of basolateral setose foveae; IV–VII each with a pair of well-developed paratergites; tergite VIII ( Fig. 5F ) semicircular, transverse; sternite IV with shallow basal transverse sulcus; posterolateral part of sternite IV shallowly concave and with densely setose patch on medial side of its shallow concavity, anterolateral part of sternite V strongly concave, its concavity glabrous ( Fig. 5E ); sternite IV–VII flat at middle; sternite VIII ( Fig. 5G ) transverse, emarginate at middle of apical margin; sternite IX ( Fig. 5H ) small, rounded, apical margin with sparce setae, with membranous plates at lateral.

Aedeagus ( Fig. 6D–F ) 0.32 mm in length, asymmetrical, sclerotized; median lobe with broad basal capsule; apical half narrowed apically, bended laterally in dorso-ventral view; apical orifice broad; parameres reduced, to form apically truncated plate; endophallus composed of long, basally twisted sclerite and short, apically bifid sclerite; base of both sclerites membranous, and base of short, apically bifid sclerite gradually obscured.

Female. Unknown.

Distribution. Japan (Amami-Ôshima Is., Kagoshima-ken, Japan)

Etymology. The new species is named after its type locality, Amami-Ôshima Island.

Comparative notes. As in the original descriptions, the antennomeres 9–10 are relatively quadrate or slightly shorter than wide in all Tyrodes species except for the new species and Tyrodes tibialis Zhang & Yin 2023 . This new species shares the elongate antennomeres 9–10 with T. tibialis but the new species is distinguished by lacking a lateral expansion of the aedeagal median lobe and lacking the small projection of each metatibia.

Among Japanese species, the new species is separated from T. segrex by a combination of the following characteristics: antennomeres 9 and 10 each longer than wide, metafemora simple, sternite IV with densely setose posterolateral patch in cavity; sternite IV–VII flat at middle (sternite IV–VII shallowly impress at middle with tufts of setae in T. segrex ), and large and elongate aedeagal endophallus.

Figures

FIGURE 5. Morphology of Tyrodes amamianus sp. nov., male. A. Dorsal habitus. B. Ventral habitus. C. Antennomere 1. D. Metaventral projection. E. Lateral side of abdomen. F. Tergite VIII. G. Sternite VIII. H. Sternite IX. Scale bars: 1.0 mm in A, B; 0.5 mm in E; 0.2 mm in D; 0.1 mm in C, F–H.

FIGURE 6. Aedeagus of Tyrodes segrex Kurbatov (A–C) and Tyrodes amamianus sp. nov. (D–F). A, D. Ventral view. B, E. Lateral view. C, F. Dorsal view. Scale bar: 0.1 mm in A–F.