Stenoscelis acutipennis Zherikhin, 1991

Stenoscelis acutipennis Zherikhin, 1991 View in CoL

[New Japanese common name: Togariba-kuchibuto-kikui-zômushi]

( Figs 1–4 View FIGURES 1–6 , 7–11 View FIGURES 7–11 , 68 View FIGURE 68–73 & 78 View FIGURE 78–83 )

Stenoscelis acutipennis Zherikhin View in CoL in Zherikhin & Egorov, 1991: 83 (type locality: “pos. Mendeleevo, Kunashir Is.”); Kojima & Morimoto, 2004 (cataloged); Hlaváč & Maughan, 2013 (cataloged); Legalov, 2020 (cataloged); Alonso-Zarazaga et al., 2023 (cataloged).

Stenoscelis sp. : Hirano et al., 2017 (recorded from Hokkaido, Japan).

Stenoscelis sp. 1 : Morimoto, 1985.

Diagnosis. Stenoscelis acutipennis can be distinguished from the other congeners (except for Stenoscelis puncticulatus Zhang, 1995 ) by having the following character states: the punctures on the disc of the rostrum being minute and almost contiguous to each other; the base of epistome being with a pair of tufts; the apex of elytra being acuminate.

Redescription. Body length 3.7–4.6 mm; black, rather shiny; mouth parts, antennae, tarsi, and apical part of tibiae reddish brown; setae yellowish brown.

Rostrum 0.5–0.6 times as long as wide; dorsum convex; dorsal surface reticulate, rugosely punctate; punctures minute on disc, medium around, almost contiguous to each other; upper margin of scrobe directed to middle of eye; epistome with a pair of tufts of long setae basally, with anterior margin obtusely projected at right side. Head with dorsal surface reticulate, smoothly punctate; punctures small, separated by interspace approximately 2–4 times as long as diameter; interocular area with a shallow fovea; eye round, hardly convex.

Antennae with club subcircular, slightly wider than long; funicle 7-segmented, slightly longer than club.

Prothorax 0.8–0.9 times as long as wide, widest before base, gradually narrowed anteriorly, weakly sinuate laterally; anterior margin weakly sinuate in middle or not; subapical constriction distinct on lateral side, obsolete on dorsal side; disc reticulate, rugosely punctate; punctures medium, separated by interspace approximately 1–2 times as long as diameter.

Elytra 1.8–2.0 times as long as wide, 1.0–1.1 times as wide as and 2.2–2.3 times as long as prothorax, subparallel, conjointly acuminate at apex; apex acutely angulated in lateral view; striae rather deep, with medium punctures separated by interspace approximately 1–2 times as long as diameter; apical part of striae moderated, not dilated or reticulate; second stria distinctly separated from base; intervals somewhat convex, with an irregular row of small puncture; base of first to fourth intervals smooth in male; base of first to third or fourth intervals rugosely punctate-granulate in female; apical half of ninth interval and tenth interval carinate; granules of intervals arranged in a single row, indistinct basally, distinct and conical on declivity; setae on declivity arranged irregularly in one or two rows, and more than twice as long as granules.

Aedeagal body (Figs 7,8) 2.5 times as long as wide, 2.5 times as long as apodeme, moderately arcuate laterally, gradually narrowed and moderately prolonged apically; apodeme attached sublaterally; endophallus without distinct sclerites; tegmen ( Fig. 9 View FIGURES 7–11 ) without dorsal part and paramere, with distinct manubrium; spiculum gastrale ( Fig. 10 View FIGURES 7–11 ) gradually curved to right side apically, not expanded apically; sternite VIII divided, with several long setae apically; without spinulate apical membranous area.

Spiculum ventral not bifurcate at base; spermatheca ( Fig. 11 View FIGURES 7–11 ) with cornu falciform; collum slightly developed; ramus not developed.

Distribution. Japan: Hokkaido, Honshu, Shikoku and Kyushu; Chishima Islands: Kunashir Is.

Biological note. In Daisenzan-rindô, Ôita Prefecture, the adults were collected on the surface of a dead broad-leaved tree ( Fig. 84 View FIGURE 84–89 ) (Takuto Hashizume & Tsubasa Nozaki pers. comm.). In Mt. Kurodake, Ôita Prefecture, many adults were found on the surface of some standing dead broad-leaved trees, which seemed to be flying on one after another on May 20, 2024. On July 21, 2024, only one adult was found on the same trees.

Non-type material. Honshu: Honshu: [Fukushima Pref.]: 1 male, Mt. Akazura, 27.VIII.2002, S. Mizunoya leg. ( KUM); [Tokyo Met.]: 1 female, Nippara, Okutama , 16.V.1970, S. Miyake leg. (KUM); [Ishikawa Pref.]: 1 male, Mt. Ôarashiyama , Hakusan-C, 8.V.2018, H. Kawase leg. (KUM); [Fukui Pref.]: 1 female, Kamiohno, Izumi Villege, Alt 700 em, 1.VI.2004, Shoji Inoue leg. (KUM); [Nara Pref.]: 1 female, Ohdaigahara , 25.VI.1984, K. Konishi leg. (KUM); [Mie Pref.]: 1 male, Myôjindaira, Mt. Myôjin-dake, Iitaka-chô , 12.VI.1998, K. Kanno leg. (KUM); [Wakayama Pref.]: 1 female, Mt. Shirama-yama , 11.V.2009, I. Matoba leg. (KUM); 2 male, ditto, 13.VI.2011 I. Matoba leg. (KUM); Shikoku: Shikoku: [Tokushima Pref.]: 1 female, Mt. Takashiro (1300 m), Kisawa-son , 23.V.1998, M. Yoshida leg. (KUM); Kyushu: Kyushu: [Fukuoka Pref.]: 2 male, Mt. Hikosan , Soeda-machi , 9.VI.2019, T. Nozaki leg. (KUM); [Ôita Pref.]: 2 female, Mt. Kurodake , 6.VIII.1987, K. Kido leg. ( KUM); 1 female, ditto, 9.VI.1996, K. Kido leg. (KUM); 2 male, Mt. Kurodake, Shônai-machi , 14.VI.1997, K. Kido leg. (KUM); 1 female, ditto, 29.VI.1997, K. Kido leg. (KUM); 1 male, 2 female, Mt. Kurodake, Kuju , 29.IV.1998, K. Kido leg. ( KUM); 1 female, Nr. Mt. Kurodake, Shônai, Yufu-shi , 24.VI.2018, R. Ito leg. (KUM); 8 male, 10 female, Near Oike Spring, Mt. Kurodake, Shonaichô Asono , Yufu-shi , 20.V.2024, Shugo Inoue leg. (KUM); 1 male, ditto, 21.VII.2024, Shugo Inoue leg. ( KUM); 2 male, Daisenzan-rindô, Ôaza Ariuji, Kujú-machi , Takeda-shi , 28.V.2023, T. Nozaki leg. (KUM).

Remarks. Stenoscelis puncticulatus Zhang, 1995 from China is very similar to Stenoscelis acutipennis in sharing some character states: the punctures on the disc of the rostrum being minute and almost contiguous to each other, the apex of elytra being acuminate. The dorsal shape of the male aedeagus of the two species is also similar to each other. However, Zhang (1995) didn’t mention the difference between S. puncticulatus and S. acutipennis . If the figure of the head of S. puncticulatus in Zhang (1995) is accurately illustrated, this species has six long setae on the epistome, but S. acutipennis have paired tufts of long setae, and this seems to be an only character that can separate two species. Further study is needed to consider whether they are different species. In this study, I identified the Japanese population as S. acutipennis , because it was described from the geographically allied area and has the identical tufts on epistome.

In this study, sexual dimorphism of the elytra were recognized for S. acutipennis : the base of first to fourth intervals smooth in male, the base of first to third or fourth intervals rugosely punctate-granulate in female; the acumination of the apex of elytra more acute in male than in female. In the original description ( Zherikhin & Egorov, 1991), the elytral base was described as smooth (based only on a holotype), but the holotype was treated as female. Therefore, the sex determination in the original description was possibly an error.