Acicnemis ryukyuana Lewis, 2023

Lewis, Jake H., Kojima, Hiroaki & Campbell, Erin O., 2025, A Japan-focused review of East Asian Acicnemis Fairmaire, 1849 (Coleoptera, Curculionidae) reveals cryptic diversity in a well-studied region, ZooKeys 1259, pp. 103-167 : 103-167

Acicnemis ryukyuana Lewis, 2023

Figs 1 , 2 F , 6 N 1–6 , 2 , 25 , 32 A, C

Type material examined

( Japan: 28). Holotype. Japan: Okinawa Prefecture: • Ishigaki, Omoto-dake , 2. VII. 1991, K. Hidetada, bears black-bordered red label reading “ HOLOTYPE / Acicnemis ryukyuana / Lewis, 2023 ”, JHL_ACI_004 , dissected male, deposited in KUM . Paratypes. Japan: Okinawa Prefecture: • Ishigaki Island, Yarabu-dake , 28. V. 1998, K. Takahashi (1, KUM), JHL_ACI_001 ; • Ishigaki Island, Omoto-dake , 2. VII. 1991, K. Hidetada (9, KUM), JHL_ACI_002 , JHL_ACI_003 , JHL_ACI_005 – JHL_ACI_011 ; • Ishigaki Island, Mt. Yarabudake , 17–20. IV. 1998, S. Ohmomo (1, KUM), JHL_ACI_012 ; • Ishigaki Island, Omotodake , 30. VI. 1974 (1, KUM), JHL_ACI_013 ; • Okinawa Island, Kunigami, Yambaru National Park, Yona Field ( 26.73972°N, 128.23630°E), 4–18. IX. 2015, A. Miyagi, Y. Tamaki, I. Maehira, L. Iha, S. Iriyama, T. Yoshida (2, OIST), OKENT 0063788 , OKENT 0063789 (dissected male) ; • Okinawa Island, Kunigami, Yambaru National Park, Yona Field ( 26.73972°N, 128.23630°E), 7–21. VIII. 2015, M. Yoshimura, M. Ogasawara (1, OIST), OKENT 0053190 (GenBank accession number: PV 255639 ) ; • Okinawa Island, Kunigami, Yambaru National Park, Yona Field ( 26.73894°N, 128.23720°E), 21. VIII – 4. IX. 2015, Y. Tamaki, T. Yoshida (2, OIST), OKENT 0055037 , OKENT 0053264 ; • Okinawa Island, Kunigami, Yambaru National Park, Yona Field ( 26.73972°N, 128.23630°E), 18. IX – 16. X. 2015, A. Miyagi, I. Maehira, T. Yoshida (1, OIST), OKENT 0053498 (GenBank accession number: PV 255640 ) ; • Okinawa Island, Hiji , 8. VII. 1974, T. Mikage (1, KUM), JHL_ACI_014 .

Non-type material.

Japan: Okinawa Prefecture: • Takeda-rindo, Ishigaki Island , 19–22. II. 2007, H. Makihara & E. Kagaya (1, KUM), JHL _AREV_625 .

Diagnosis.

Body length 3.2–5.0 mm. Covered in dark gray, black, and bright yellow scales, with a black-bordered, yellow spot at the center of each elytron. Apex of elytra covered in yellow scales, and contrasting with overall dark dorsal surface of elytra. Pronotum lacking impunctate longitudinal midline (present in A. koguma ), but with an M-shaped band of yellow scales. Scutellum small, red, shiny, and largely bare over dorsal surface. Elytra with long, erect scales only on odd intervals. Sclerolepidia distinct and protruding. Third tarsomeres weakly emarginate to truncate (Fig. 2 F ). Pedon with lateral edges approx. parallel in dorsal view, but converging evenly into a blunt, rounded point. Internal sac not visible inside aedeagus, but with protruding basal structure that bears a distinctive U-shaped formation anteriorly at its apex (Fig. 6 N 1 – 2 ).

Distribution.

This species is known only from Okinawa Prefecture, Japan (Yambaru National Park ( Okinawa Island) and forested regions of Ishigaki Island.

Remarks.

This species is very distinct from other Japanese Acicnemis and its range-restricted, endemic presence in pristine, subtropical rain forest dominated parts of Okinawa Prefecture was hitherto a mystery. However, preliminary morphological and molecular evidence suggest a sister relationship between A. ryukyuana and an undescribed Southeast Asian (Thai) species that possesses emarginate third tarsomeres. Acicnemis ryukyuana likely represents a lineage that was isolated from the undescribed Thai species lineage when the Ryukyu Islands separated from mainland Asia (see Osozawa et al. 2011) and evolved truncate third tarsomeres as derived character.

Figures

Figure 1. Maximum likelihood tree of twelve Acicnemis species based on a 300 base-pair long CO 1 gene fragment constructed in IQ-TREE v. 1.6. 12 using a GTR + F + I + G 4 model. Branch support values represent standard nonparametric bootstraps (1000 replicates). Bootstrap values less than 75 are not displayed on the tree. The codes MEBLA 191-14, VVGPL 2845-15, and OWEVG 891-15 are BOLD Systems accession numbers, whereas all other codes are GenBank accession numbers. Associated Acicnemis weevil figures on the right of the tree are approximately to scale.

Figure 2. Diagnostic morphological characters in Acicnemis. A. A. azumai Morimoto & Miyakawa, 1995 (JHL _ ACITAI _ 081) showing lack of prominent posterior prosternal projections; B. A. laeta Hubenthal, 1919 (JHL _ AREV _ 533) showing prominent prosternal projections; C. A. kiotoensis Nakane, 1963 (JHL _ AREV _ 982) showing antenna with the second funicular antennomere longer than antennomeres 3 + 4; D. A. koguma Lewis & Kojima, sp. nov. (JHL _ SYN _ 141) showing antenna with the second funicular antennomere shorter than antennomeres 3 + 4; E. A. luteomaculata Morimoto & Miyakawa, 1995 (JHL _ AREV _ 189) showing truncate third tarsomere; F. A. ryukyuana Lewis, 2023 (JHL _ ACI _ 011) showing weakly emarginate third tarsomere; G. A. maculaalba Roelofs, 1875 (JHL _ AREV _ 577) showing strongly emarginate third tarsomere.

Figure 6. Aedeagi of Acicnemis. A 1–2. A. albofasciata (Ter-Minasian 1953); B 1–2. A. azumai Morimoto & Miyakawa, 1995; C 1–2), A. cryptica Lewis & Kojima, sp. nov.; D 1–2. A. dividicincta Morimoto & Miyakawa, 1995; E 1–2. A. exilis Morimoto & Miyakawa, 1995; F 1–2. A. kiotoensis Nakane, 1963; G 1–2. A. laeta Hubenthal, 1919; H 1–2. A. luteomaculata Morimoto & Miyakawa, 1995; I 1–2. A. maculaalba Roelofs, 1875; J 1–2. A. nobilis Hubenthal, 1919; K 1–2. A. nohirai Morimoto & Miyakawa, 1995; L 1–2. A. palliata Pascoe, 1872; M 1–2. A. postica Hubenthal, 1919; N 1–2. A. ryukyuana Lewis, 2023; O 1–2. A. sauteri Hubenthal, 1919; P 1–2. A. shibatai Voss, 1971; Q 1–2. A. shigematsui Morimoto & Miyakawa, 1995; R 1–2. Acicnemis sp. 1; S 1–2. A. squamata Lewis & Kojima, sp. nov.; T 1–2. A. suturalis Roelofs, 1875.

Figure 25. Acicnemis ryukyuana Lewis, 2023 (OKENT 0063788). A. Lateral; B. Dorsal. Scale bar: 1 mm.

Figure 32. X-ray μCT generated 3 D models of two Acicnemis species. The colored parts in the segmented models below represent hindwing (in blue), metanotum + dorso-longitudinal flight muscles (in green), and dorso-ventral flight muscles (in orange). A. A. ryukyuana Lewis, 2023 (OKENT 0053498) dorsal view with scales removed, showing a relatively smooth pronotum and distantly spaced punctures; B. A. albofasciata (Ter-Minasian, 1953) (JHL _ AREV _ 782) dorsal view with scales removed, showing a moderately rugose to roughened pronotum with interspaces between punctures much smaller; C. A. ryukyuana segmented model with the right elytron removed, showing a comparively larger metanotum and dorso-longitudinal flight muscles relative to the elytra (~ 30 %); D. A. albofasciata showing a comparatively smaller metanotum and dorso-longitudinal flight muscles relative to the elytra (~ 23 %).