Acicnemis ryukyuana Lewis, 2023

Lewis, Jake H., 2023, A New Species of Acicnemis Fairmaire, 1849 (Coleoptera: Curculionidae) from Okinawa and Ishigaki Islands, Okinawa Prefecture, Japan, The Coleopterists Bulletin 77 (2), pp. 185-188 : 186-188

Acicnemis ryukyuana Lewis , new species

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Fig. 1

Diagnosis. Acicnemis ryukyuana ( Figs. 1A–E ) is separated from congeners by the following combination of characters: elytra covered in light to dark gray scales with three black, suberect scale patches (one surrounding scutellum, one at middle of elytra near suture, one at subapical third of elytra near suture) and with conspicuous V-shaped, yellow scale band on pronotum and elytral humeri. Yellow scale patch also in center of elytra and with another large yellow patch apically. Body with white to light grayish scales ventrally. Base of rostrum, pronotum and odd elytral intervals with thick, erect, dark gray and yellow scales which are as long or longer in length than tarsal claws. Funicle with second antennomere shorter than or subequal to first antennomere. Metatibia only curved in basal third. Third tarsomere very weakly emarginate ( Fig. 1E ), not deeply emarginate over more than one-third of tarsomere length (as in Fig. 1F ).

Description. Body length (excluding rostrum): 3.2–5.0 mm; body width at widest point 1.6–2.1 mm; see Diagnosis for scale patterning (except leg pattern). Head: Rostrum evenly curved and nearly as long as pronotum; with white- to tan-colored scales up to antennal insertion; distal half of rostrum bare and with fine punctures. Scape of antenna inserted slightly before midpoint of rostrum, bare on basal third, with tan-colored scales on distal twothirds. First antennomere of funicle approximately equal in length to second antennomere. Antennal club without conspicuous elongate “stem” at base (e.g., as in Acicnemis maculaalba Roelofs, 1875 ). Pronotum: Length approximately equal to width; sides evenly curved in dorsal view, and parallel at base. Elytra: 2.6–2.8 times longer than pronotum; base sinuate; widest at basal fourth; punctures very deep, each bearing scale. Legs: Femora flattened in basal half, and with swollen region bearing a conspicuous ventral tooth preapically; bearing both flattened, circular scales and erect ones (gray or white). Each tooth and swollen area of same size on all femora. Tibiae curved in basal half with gray scales, curved in distal half with white scales; bearing large, curved apical spur dorsally and dense group of erect setae of same length ventrally. Tarsomere 1 equal or subequal in length to tarsomeres 2 + 3 combined; tarsomere 3 shallowly emarginate, depth of emargination not exceeding one-third of tarsomere length; apical tarsomere (pretarsus) subequal in length to first tarsomere; pretarsal claw simple. Abdomen: Suture between ventrite 1 and 2 sinuate; sutures between other ventrites transverse, straight; longitudinal length of ventrite 1 at middle approximately equal to length of ventrite 2; longitudinal length of ventrites 3 and 4 equal; longitudinal length of ventrite 5 approximately equal to ventrites 3 + 4 combined. Male genitalia: Penis ( Figs. 1C, D ) with apex evenly rounded and sides subparallel; internal sac with small square to quadrilateral shaped sclerite and protruding structure which extends past tegmen ring; tegmen ring open.

Specimens EXamined. Holotype: Japan: Ishigaki, Omoto-dake , 2.VII.1991, K. Hidetada, KUM, JHL_ACI_004 . Paratypes: 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_5–JHL_ACI_011 ; Ishigaki Island, Mt. Yarabudake , 17–20.IV.1998, S. Ohmono (1, KUM), JHL_ACI_012 ; Ishigaki Island, Omoto-dake , 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), OKENT0063788 , OKENT0063789 ; Okinawa Island, Kunigami, Yambaru National Park , Yona Field (26.73972°N, 128.23630°E), 7–21.VIII.2015, M. Yoshimura, M. Ogasawara (1, OIST), OKENT0053190 ; 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), OKEN T0055037 , OKENT0053264 ; 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 ; Okinawa Island, Hiji , 8.VII.1974, T. Mikage (1, KUM), JHL_ACI _014.

Comparisons with Related Species. Acicnemis ryukyuana is immediately recognized by the distinct pattern of gray, black, and yellow round, flattened scales and comparatively long (equal to or longer in length than tarsal claws), erect, black and yellow scales on the rostrum, pronotum, and odd elytral intervals. In Japan and Taiwan, the only other recorded species with similarly long, erect scales is Acicnemis costulifera Hubenthal, 1919 , which has distinctly ridged even elytral intervals and a coarsely granulate pronotum. Acicnemis ryukyuana is also one of the few in the genus with shallowly emarginate tarsal claws; a few other species in East Asia share this character, namely Acicnemis lutomaculata Morimoto and Miyakawa, 1995 and Acicnemis biarcuata Hubenthal, 1917 .

Etymology. The specific name ryukyuana is a reference to the Ryukyu Islands where this species has been collected (see Fig. 1G ). I also suggest the Japanese common name リュウキュウカレキゾウムシ [Ryukyu-kareki-zômushi] for this species, which translates in English to “Ryukyu dead-tree weevil”.

Comments. Despite SLAM traps having been deployed widely at 24 sites across Okinawa Island from 2015–2018 by OIST researchers, and unlike several other species of Acicnemis which were widely collected in traps across Okinawa Island, A. ryukyuana was only collected in small numbers on Okinawa Island from one site (Yona Field, Yambaru National Park). Similarly, collection records from Ishigaki Island are also all from well-preserved subtropical forest areas. Relative to other species of Acicnemis in the Ryukyu Islands, this suggests that A. ryukyuana is comparatively more sensitive to anthropogenic disturbance and only persists in well-preserved forest habitats. Notably, although Yambaru National Park is well preserved as a UNESCO Natural Heritage Site, parts of Ishigaki Island where A. ryukyuana was collected are not as well protected. Furthermore, the host plant(s) remains unknown for this species and would be worth investigating in future field studies.

Here, A. ryukyuana is placed in the present genus based on the open tegmen of the aedeagus ( Figs. 1C, D ; closed in Karekizo and Trachodes ), possessing fully developed hind wings (absent in Trachodes ), possessing a prominent scutellar shield (absent or reduced in Trachodes ), possessing parallel sided elytra and a relatively elongate body form (ovate and rounded in Trachodes ), and possessing a smooth pronotum (with longitudinal ridges in Karekizo ). Although Morimoto and Miyakawa (1995) used the emargination of the third tarsomere (or lack thereof) to separate Acicnemis (emarginate) from Trachodes and Karekizo (truncate), it was found here that A. luteomaculata also has truncate third tarsomeres. Furthermore, the European species Trachodes hispisdus (Linnaeus, 1758) has emarginate third tarsomeres. Thus, although the shape of the third tarsomere is very useful for separating the species and species groups, it cannot be used alone to separate Acicnemis , Karekizo , and Trachodes as some exceptional species exist. In general, few of the characters traditionally used to separate these genera hold for all species and many intermediate forms exist. A preliminary molecular study of the tribe is currently in preparation with the hope of elucidating the phylogenetic relationships of the aforementioned genera.

Figures

Fig. 1. Acicnemis ryukyuana, new species: A) Lateral view, B) Dorsal view, C) Aedeagus (lateral), D) Aedeagus (dorsal), E) Shallowly emarginate third tarsomere of foreleg with tarsal claw removed for visibility. Acicnemis postica Hubenthal, 1917: F) Deeply emarginate third tarsomere of foreleg with tarsal claw removed for visibility. G) Map of localites (Okinawa and Ishigaki Islands, Japan) of A. ryukyuana, new species.