Walteriella kasugana, Hsiao & Okushima, 2025

Walteriella kasugana sp. nov.

Figs. 1F View FIGURE 1 , 3L–M View FIGURE 3 , 6A–D, F View FIGURE 6 , 7D View FIGURE 7 , 8D View FIGURE 8 , 9D View FIGURE 9 , 10 View FIGURE 10

Type material. Holotype: ♂: “ 11.IV.2025 / TAIWAN: Jinshuiying , 1555m / 22°24’17”N, 120°45’31”E / Tahanshan, Chunri, Pingtung / M. Geiser, M. Fikáček / B.-H. Ho & G.-J. Phang leg. // HOLOTYPE / Walteriella kasugana / Hsiao & Okushima, 2025” ( NMNS) GoogleMaps . Paratypes: 2 ♂: “ 27.IV.2014 / Jinshueiying, Pingtung / Taiwan / W.-C. Liao leg. // PARATYPE / Walteriella kasugana / Hsiao & Okushima, 2025” ( 1 in NHMUK, 1 in YHC) ; 2 ♂: “ Taiwan: Pingtung / Tahanshan / 30.IV.2014 leg. Y.-T. Chung // PARATYPE / Walteriella kasugana / Hsiao & Okushima, 2025” ( TARI) ; 1 ♀: “ 2.V.2020 / Tahanshan, Chunri, / Pingtung, Taiwan / F.-S. Hu & I.-L. Lee leg.” ( NMNS) .

Diagnosis. Adults of this species can be readily distinguished from other Taiwanese Walteriella species by their unique yellowish-brown elytra with black head, thorax and legs ( Figs. 1F View FIGURE 1 , 3L–M View FIGURE 3 ). This species is similar to W. brunnea in general shape of the aedeagus and female genitalia and some specimens of W. brunnea exhibit more or less yellowish coloration ( Fig. 3B, G View FIGURE 3 ). However, in addition to its characteristic elytral coloration, W. kasugana can be further distinguished from W. brunnea by the following characters (states of W. brunnea in parentheses): shorter elytra in males, about 3.4–3.6 times as long as wide (more elongate, about 3.8–4.0 times as long as wide); aedeagus: the base of median lobe smaller in lateral view ( Fig. 6B, F View FIGURE 6 ) (larger and more globular and swollen; Figs. 5F View FIGURE 5 , 6E View FIGURE 6 ); female genitalia: accessory gland about 1.3 times as long as diverticulum ( Fig. 8D View FIGURE 8 ) (about 2.0 times as long as diverticulum; Fig. 8B View FIGURE 8 ).

Description

Male ( Fig. 3L View FIGURE 3 ). Length: 7.7–8.2 mm ( holotype: 8.2); width: 1.5–1.7 mm ( holotype: 1.7). Eyes black. Head black, lateral sides of clypeus pale. Antennae dark brown to black, with antennomere I brown basally. Mandibles brown, with apices darker; maxillary and labial palpomeres black, with apices of terminal maxillary palpomeres brown. Pronotum black, with posterior margin yellowish brown. Scutellum black. Elytra yellowish brown; meso- and metaventrites black; abdomen dark brown to black. Legs black, with coxae pale distally. Body densely covered with fine yellowish pubescence; anterior margin of clypeus fringed with yellowish bristles; antennae, elytra and legs with some yellowish bristles intermingled with primary pubescence, but sparsely at humeri.

Head as long as wide, eyes moderately protruding, approximate ratio of eye diameter to interocular space 1.0:2.7–4.3; dorsum slightly swollen posteriorly, depressed along anterior margin of clypeus and laterally anterior to eyes; anterior margin of clypeus arcuate, slightly emarginate medially; surface densely, finely punctate, each side with rectangular impression posterior to antennal socket; antennae filiform and long, extending to apical fourth of elytra, antennomere I clavate, II short and expanded apically, III–XI subcylindrical, with a small groove on each segment, approximate ratio of antennomere lengths as follows: 20.8:10.0:20.0:27.5:26.3:27.5:25.6:25.6:22.5:21.3:20.6.

Pronotum trapezoidal, about 0.71 times as wide as head, about 1.18 times as long as wide; anterior and posterior margins arcuate; lateral sides widening anteriad, distinctly constricted in anterior third, marginated in anterior half; anterior angles somewhat expanded and rounded; posterior angles slightly protruding and obtuse; disc swollen, with pair of rounded elevations posterolaterally; antero-lateral areas hollowed; medio-longitudinal furrow distinct in centre of disc; surface semilustrous, finely and sparsely punctate. Scutellum triangular with obtuse apex. Elytra collectively about 1.5 times as wide as pronotum, about 3.4–3.6 times as long as wide, lateral margins subparallel, moderately narrowed apically; surface densely and coarsely punctate. Prosternal process concave apically. Mesoventrite distinctly convex medially. Legs very slender; femora nearly straight; tibiae nearly straight but somewhat bent; tarsi with tarsomere I–III emarginate and IV bilobed; claws simple.

Aedeagus ( Figs. 6A–D, F View FIGURE 6 ). Oval; globular and swollen dorsally at base. Ventral process of each paramere subcylindrical, slightly narrowed apically, slightly bent inwards; dorsal plate of each paramere with one well-developed apical tooth from caudal view, slightly longer than ventral process, distinctly curved inwards, rounded apically, forming a broad, oval middle emargination; laterophyses closely next to each other, distinctly bent dorsad, apically rounded, distinctly exceeding the middle emargination of dorsal plate.

Female ( Fig. 3M View FIGURE 3 ). Length: 9.7 mm; width: 1.9 mm. Similar to male. Body and pronotum wider than male; head as long as wide, eyes less protruding than in male, approximate ratio of eye diameter to interocular space 1.0:4.1; antennae shorter than male, extending to elytral midlength, approximate ratio of antennomere lengths as follows: 15.0:10.0:17.0:16.0:15.0:15.0:16.0:15.0:14.0:12.0:12.0. Pronotum about 0.90 times as wide as head, about 1.05 times as long as wide. Elytra collectively about 1.4 times as wide as pronotum, about 3.7 times as long as wide. Abdominal ventrite VII ( Fig. 7D View FIGURE 7 ) with lateral margins weakly arcuate, terminal margin slightly sinuate laterally, with submedian rounded lobe on each side, angularly emarginate medially, with an oval, apically rounded and weakly sclerotised membrane behind the middle emargination. Female genitalia ( Fig. 8D View FIGURE 8 ) with vagina elongate and stout apically; diverticulum weakly spiralling, much longer than spermathecal duct; spermatheca with a weakly spiral and long tube, longer than diverticulum; accessory gland long, about 1.3 times as long as diverticulum.

Derivation of name. The specific epithet is a Latinised adjective derived from ‘Kasuga’, the Paiwan name for Chunri Township, referring to the only currently known distribution of the species. Chunri is an indigenous mountain township in Pingtung County, Taiwan, primarily inhabited by the Paiwan people.

Distribution and natural history. This species is known only from Mt. Tahan, Chunri Township, Pingtung County, Taiwan ( Fig. 9D View FIGURE 9 ), with occurrence records spanning from middle April to early May and primarily concentrated in late April ( Fig. 10 View FIGURE 10 ). Although it appears to be sympatric with its closely related W. brunnea at Mt. Tahan, population of W. brunnea at Mt. Tahan is primarily recorded from late March to middle April, whereas the majority of specimens of W. kasugana were collected in late April to early May, with only a single record dated April 11.