Rimboda saekii Fujisawa & Lewis, 2025

Rimboda saekii Fujisawa & Lewis , new species

[Japanese common name: Ryukyu-nise-kagiashi-kumo-zoumushi]

http://zoobank.org/ urn:lsid:zoobank.org:act:B1E32C95-232A-4895-BF33-C7B9F614E1B2

Figures 2 View FIGURE 2 , 3 View FIGURE 3

Brimoda sp. 1 : Sugimoto, 2022: 40 (habitus photograph).

Diagnosis. Rimboda saekii ( Fig. 2 View FIGURE 2 ) is immediately distinguished from its congeners by the black-scaled dorsum with distinct, white-scaled patches in the middle of the pronotum and a white-scaled T-shaped region at the apex of the elytra.

Description. Male: Body length: 2.4–4.0 mm; body width at widest point 1.0– 1.9 mm. Color pattern: Cuticle black to dark red. Legs and venter covered in bright white scales, except for prosternal canal which is covered in yellow-orange scales. Dorsal half of head covered in black scales. Pronotum largely covered by black scales, but also with sparsely scattered orange scales and four prominent patches of white scales (two at postero-lateral corners of pronotum, one at posterior edge of pronotum medially, and one more along middle of pronotum near anterior edge). Scutellum covered in bright white scales. Elytra largely covered by black scales, but also includes sparsely distributed orange scales and white patches in following regions: (1) at base of elytra, (2) longitudinally along first elytral interval at middle of elytra, (3) along 6 th and 7 th elytral intervals laterally, and (4) in T-shaped patch at elytral apex. Head: Rostrum straight in basal half, evenly curved in apical half; distal half of rostrum bare and with fine punctures. Scape of antennae slightly curved and inserted after midway point of rostrum, but before apical 3 rd; first segment of funicle approximately equal in length to second segment. Eyes nearly touching ventrally, converging dorsally, creating conspicuous open region between eyes centrally. Pronotum: Length slightly wider than long; coarsely punctured; with conspicuous longitudinal carina in center of pronotum (absent near anterior and posterior edges of pronotum) ( Fig. 2C View FIGURE 2 ). Prosternum: weakly depressed before coxae and bordered weakly by broad keels. Elytra: Sinuate at base; scutellum large and square shaped (covered in white scales); conspicuously carinate ( Fig. 2D View FIGURE 2 ). Legs: Forecoxae with ventral projection. Femora roughly of equal width across length; bearing small tooth at midpoint ventrally, and with another smaller tubercle of varying size apically after tooth. Hind femora weakly exceeding elytral apices. Tibiae stout, each bearing a large apical spur. 1 st tarsal segment as long as 2 nd + 3 rd tarsal segment; 3 rd tarsal segment bilobed; tarsal claws simple. Abdomen: First ventrite concave. Sulcus between 1st and 2 nd largely straight, but somewhat sinuate at edges laterally; sulci between other externally visible segments transverse (i.e., straight); length of 2 nd segment slightly wider than 3 rd or 4 th segments; apex of 5 th segment without white scales medially. Male Genitalia: Penis with edges diverging laterally and coming to a rounded point at apex ( Fig. 3A View FIGURE 3 ). Internal sac with M-shaped structure visible inside the aedeagus. Female: Forecoxae without ventral projection. First ventrite convex or flat. Tergite 8 shaped sub-triangle ( Fig. 3E View FIGURE 3 ); spermatheca with ramus and collum close to each other, differentiated ( Fig. 3H View FIGURE 3 ); spermathecal duct short.

Material Examined

HOLOTYPE: JAPAN: Okinawa Prefecture: Okinawa Island, Kunigami, Oku , 13.VI.2003, H. Makihara (male, TUA).

PARATYPES: JAPAN: Kagoshima Prefecture: Amami-oshima Island, Nishinakama , 1–7.VI.1970, H. Makihara, (1 male, KUM) ; Amami-oshima Island, Nishinakama , 3–5.VIII.1969, H. Makihara, (1 female, KUM) ; Amami-oshima Island, Hatsuno , 26.VI.1970, I. Matoba, (1 male, KUM) ; Amami-oshima Island, Shinmura , 12.VI.1962, M. Sato, (1 male, KUM) ; Tokunoshima Island, Amagi town, Mikyo , 15.V.1976, J. Okuma / (1 female, KUM) ; Okinawa Prefecture: Okinawa-jima Island, Kunigami vill., Okuni-Rindo , 15.VI.2014 (emerged from Distylium racemosum ), H. Nishino, (1 female, TUA) ; Okinawa-jima Island, Kunigami vill., Hedo , 14.V.2017, H. Nishino, (1 male, TUA) ; Okinawa-jima Island, Kunigami vill., Yona , 2.VI.2021, T. Saeki, (1 male, TUA) ; Okinawa-jima Island, Kunigami vill., Yona , 27.IV.2021, T. Saeki, (1 male, 3 females, TUA) ; Okinawa-jima Island, Kunigami vill., Yona , 18.XI.2021 ~ 5-19.V.2022 (emerged from Distylium racemosum ), T. Saeki, (6 females, TUA) ; Okinawa-jima Island, Kunigami vill., Mt. Nishime-dake , 2.VI.2021, H. Sawada, (1 male, TUA) ; Okinawa-jima Island, Kunigami, Oku , 26.VI.2003, H. Makihara, (1 male, TUA) ; Okinawa-jima Island, Kunigami vill., Benoki , 1.I–4.VI.1988 (emerged from Distylium racemosum ), S. Furihata, (1 male, KUM) ; Okinawa-jima Island, Hiji , 9.VII.1974, T. Mikage, (1 female, KUM) ; Ishigaki-jima Island, Mt. Omoto-dake , 11.VI.1974, T. Mikage, (1 female, KUM) ; Okinawa-jima Island, Kunigami, Yambaru Manabi-no-mori (26.72256°N, 128.26027°E), 13–27.V.2016, (1 male, OIST), OKENT0091309 GoogleMaps ; Okinawa-jima Island, Kunigami, Oku (26.83604°N, 128.27191°E), 10– 24.VI.2016, (1 male, OIST), OKENT0089308 GoogleMaps ; Okinawa-jima Island, Kunigami, Oku (26.83630°N, 128.27051°E), 29.IV–13.V.2016, (1 female, OIST), OKENT0087120 GoogleMaps ; Okinawa-jima Island, Kunigami, Yona Field (26.73894°N, 128.23720°E), 29.IV–13.V.2016, (1 male, 1 female, OIST), OKENT0061634 , OKENT0061635 GoogleMaps .

Okayama Prefecture (dubious collection record): Tsuyama city, Shimotakakura-nishi , 6.VI.1992, M. Fukuda, (1 male, TUA) .

Distribution: Japan (Ryukyu Island: Amami-oshima, Tokunoshima, Okinawa-jima and Ishigaki-jima). The specimen apparently collected from Okayama Prefecture is dubious and is reported here only as a formality.

Ecology: The larvae have been reared from Distylium racemosum Siebold & Zucc. ( Hamamelidaceae ).

Etymology. The specific name “ saekii ” honors the contributions of Mr. T. Saeki, who graciously collected specimens for use in the current paper.

Comments. Malaise trap data (OIST insect collection) and collection data from other islands (TUA, KUM) suggest that R. saekii only occurs in natural, Ryukyu subtropical forest areas. Notably, one comparative field study of eleven potential indicator plant species in Yanbaru National Park found the presence of large Distylium racemosum (the host plant of R. saekii ) trees was strongly associated with forest age and old-growth forests ( Abe et al. 2020). The recorded host plant and collection records of R. saekii suggest that this species is a natural, endemic element of the Ryukyu fauna, and is also sensitive to anthropogenic disturbance. The discovery of Rimboda from the Ryukyu Islands of Japan represents a significant extension to the known geographic range of the genus as the other described species are known from Malaysia, Indonesia and Philippines. We place R. saekii in Rimboda based on the prosternum weakly depressed before coxa, lacking a ventral canal and hind femora extended beyond elytral apices.