Bisayodes Wakimura & Jałoszyński, 2023

Jałoszyński, Paweł & Wakimura, Ryotaro, 2023, A new genus, new species and new records of Eucinetidae in Japan and Taiwan (Coleoptera), Zootaxa 5351 (1), pp. 122-138 : 124-128

Genus Bisayodes Wakimura & Jałoszyński , gen. n.

Type species: Bisayodes hure Wakimura & Jałoszyński , sp. n.

Diagnosis. Body small, not reaching 2 mm in length, short oval; head subpentagonal with antennal insertions not exposed in dorsal view; frons not constricted in front of eyes; frontoclypeal margin carinate; clypeus exposed in dorsal view, about 6 × wide as long at middle; mouthparts semisuctorial, with labrum and prelabium about twice as long as broad and truncate apically; mentum as long as wide; labial palpomere 2 pedunculate; labial palpomere 3 fusiform and rapidly narrowing in distal third; galea vestigial, lacinia longer than stipes and with several conspicuously short and widely spaced thick distomesal setae; maxillary palpomere 1 subtriangular and shorter than palpomere 2; maxillary palpomere 2 subcylindrical; maxillary palpomere 3 fusiform, nearly gradually narrowing distally; antenna loosely assembled, with slender and elongate proximal antennomeres and clearly delimited trimerous club; mesoventral process broadly subtriangular and not separating mesocoxae; metaventrite behind mesocoxae with transverse carina; median region of metaventrite broadly subtriangular and posteriorly reaching behind half length of metacoxal plates; apical mesotibial spurs of subequal length and apically rounded; elytra lacking adsutural striae and transverse strigulae; parameres shorter than penis and lacking setae.

Description. Body ( Figs 1 , 5–6 ) short oval and strongly convex dorsally, not reaching 2 mm in length.

Head ( Figs 7–12 ) flattened and transverse, subpentagonal with tempora strongly converging posteriorly and sides of frons strongly converging anteriorly. Vertex and frons confluent; anterior margin of frons demarcated from clypeus by arcuate transverse carina laterally extending along mesal margins of eyes; clypeus visible in dorsal view, arcuate, about 6 × as wide as long. Eyes convex. Each gena with infraocular carina. Antennal sulcus present at each side of head, extending ventrally from antennal fossa to lateral margin of submentum, with carinate outer edge ( Figs 8–10 ).

Gular plate subrectangular, slightly transverse; gular sutures distinct.

Mouthparts ( Figs 13–19 ) semisuctorial. Labrum ( Fig. 13 ) trapezoidal, elongate, with truncate anterior margin, together with prelabium forming tubular sucking apparatus ( Fig. 9 ). Mandibles ( Fig. 14 ) short, elongate subtriangular and flattened, with weakly sclerotized apical subtriangular and pointed tooth directed anteriorly, mesal margin sharp, with short and broad preapical tooth and lacking prostheca and mola. Maxillae ( Figs 15–17 ) with slender stipes and palpifer, galea vestigial, presumably represented by narrow and short slender projection at base of maxillary palp; lacinia slender and weakly curved, slightly longer than stipes, with a few short and sparse distomesal setae. Maxillary palp tetramerous, palpomere 1 smallest, elongate, asetose; palpomere 2 subtriangular, weakly elongate and shorter than 3, with only a few setae; palpomere 3 subcylindrical with oblique distal margin, sparsely setose; palpomere 4 largest, fusiform and nearly gradually tapering apically, sparsely setose on entire surface. Labium ( Figs 8 , 18–19 ) with strongly transverse and short, slightly impressed submentum, trapezoidal mentum with lateral and anterior marginal carinae, and elongate, subtrapezoidal prelabium truncate at apex; premental sclerites absent. Labial palps inserted at base of prelabium, trimerous, palpomere 1 vestigial, subtriangular, asetose; palpomere 2 pedunculate, strongly broadening distally to middle and then strongly narrowing, covered with sparse setae; palpomere 3 about as long and about half as wide as 2, fusiform with rapidly narrowing apical region, sparsely setose.

Antenna ( Figs 10–12 ) slender, with enlarged scape, elongate pedicel and elongate proximal flagellomeres, distally thickened to form distinct trimerous club. All antennomeres covered with long setae.

Pronotum ( Fig. 5 ) strongly transverse and strongly convex, with anterior and lateral margins confluent and broadly rounded, posterior margin strongly arcuate and posteriorly convex in middle, laterally strongly emarginate, so that posterior pronotal corners are projecting posterolaterally. Lateral pronotal edges visible in ventral view; hypomera concave; prosternum short, in front of procoxae nearly carinate; prosternal process narrow, rounded at apex, not projecting ventrally beyond ventral surface of procoxae.

Mesoscutellar shield not exposed in intact beetles.

Elytra ( Fig. 5 ) strongly convex, oval, lacking fine transverse strigulae and lacking adsutural striae, with subhorizontal epipleurae ( Fig. 6 ) weakly, gradually narrowing posteriorly.

Mesoventrite ( Fig. 20 ) short, anteriorly concave and posteriorly convex, with impressed and broad procoxal rests in its anterior region; posteriorly, median region of mesoventrite forming short and broadly subtriangular mesoventral process entirely situated in front of mesocoxae; median region of mesoventrite forming demarcated elongate rhomboidal plate with median longitudinal impression.

Metaventrite ( Fig. 20 ) with median region broadly subtriangular and bearing anterior transverse carina behind mesocoxae; posterior tip of median region of metaventrite reaching distinctly behind middle of metacoxal plates; metanepisterna not exposed in ventral view. Large metacoxal plates meeting along midline behind median region of metaventrite, with posterior margin of each plate forming two angles: outer rounded and more posterior and inner (mesal) more subtriangular and less projecting posteriorly; lateral margin of each metacoxal plate weakly rounded in anterior and posterior thirds, at middle straight.

Fore legs ( Figs 6 , 21 ) with strongly transverse procoxae, each bearing ventral lateral carina on entire length; protrochanters small, subtriangular; profemora ( Fig. 21 ) flattened laterally, slightly narrowing distally, each with anteroventral row of dense thick and slightly unevenly distributed setae in basal half; protibiae ( Fig. 21 ) about as long as profemora, broadening distally and flattened dorsoventrally, lacking apical spurs, with ventral and dorsal apical rows of densely set thick trichia; protarsi ( Fig. 21 ) longer than half length of tibiae, with tarsomeres 1–4 subequal in lengths, subcylindrical, tarsomere 5 elongate, subcylindrical, with pair of unmodified claws.

Middle legs ( Figs 20, 22 ) with strongly transverse mesocoxae slightly longer than procoxae and each also bearing posteroventral carina, distal coxal region above coxo-trochanteral articulation projecting mesally as subtriangular tooth; mesotrochanters small, subtriangular; mesofemora flattened dorsoventrally and narrowing distally; mesotibiae indistinctly shorter than mesofemora, flattened dorsoventrally and broadening distally, each with apical transverse row of dense and thick trichia along ventral and dorsal margin, and with two apical mesal spurs ( Fig. 22 ) of similar lengths, slightly curved in apical regions and blunt; mesotarsi ( Fig. 22 ) shorter than mesotibiae, similar to protarsi but with tarsomere 1 strongly elongate.

Hind legs ( Fig. 20 ) with coxae hidden under metacoxal plates; metatrochanters small and subtriangular; metafemora, metatibiae and metatarsi similar to those in middle legs, but femora with apical spurs gradually narrowing to pointed apices, and metatarsi slightly longer than mesotarsi.

Abdomen ( Fig. 6 ) with five visible ventrites, the first longest, but largely hidden under metacoxal plates.

Aedeagus ( Fig. 37 ) with parameres devoid of setae and shorter than slender penis.

Distribution and composition. One species inhabiting northern Japan: Hokkaidô.

Etymology. The name Bisayodes (gender masculine) is derived from the genus Bisaya .

Remarks. Bisayodes can be distinguished from all other extant genera of Eucinetidae by the following set of characters: semisuctorial mouthparts, antennae slender with trimerous clubs, antennal fossae not exposed in dorsal view, and the carinate frontoclypeal border demarcating a relatively long, dorsally clearly visible clypeus (see identification key for genera of Eucinetidae given below). Among the genera with suctorial or semisuctorial mouthparts, Bisayodes is most similar to Bisaya and Tohlezkus . It differs from Bisaya in: (1) head pentagonal, with anterior margin strongly convex (in Bisaya hexagonal, with anterior margin truncate); (2) head not constricted at antennal insertions, hence antennal fossae not exposed in dorsal view (in Bisaya head strongly constricted and antennal fossae exposed in dorsal view); (3) frontoclypeal border carinate (in Bisaya frons and clypeus confluent); (4) labial palpomere 3 fusiform, broadest near proximal third and strongly narrowing distally, with strongly sinuate outer margin, about half as wide as palpomere 2 and as long as palpomere 2 (in Bisaya labial palpomere 3 nearly filiform, very slender, with outer margin nearly straight, as wide as 1/4 width of palpomere 2 and longer than palpomere 2); (5) maxillary palpomere 1 subtriangular and shorter than palpomere 2 (in Bisaya subcylindrical and clearly longer than 2); (6) galea vestigial, lacinia much longer than maxillary palpomere 1 and 2 combined, with a few widely spaced and conspicuously short distomesal setae (in Bisaya galea distinct, lacinia clearly shorter than palpomeres 1 and 2 combined, with distomesal group of dense long setae); (7) postcoxal carina or line on metaventrite at middle straight (in Bisaya forming subtriangular expansion between mesocoxae projecting anteriorly); (8) median region of metaventrite with its apex posteriorly reaching far behind middle length of metacoxal plates (in Bisaya apex of median region of metaventrite not reaching middle of metacoxal plates). Bisayodes differs from Tohlezkus in: (1) antennae loosely assembled with antennomeres 1–5 elongate and well-defined trimerous club (in Tohlezkus antennae massive, compact and with antennomeres 2–10 transverse); (2) mouthparts semisuctorial, with labrum and prelabium about twice as long as broad and with truncate anterior margins (in Tohlezkus mouthparts suctorial, with labrum and prelabium more than twice as long as broad and apically pointed); (3) maxillary palpomere 2 subtriangular, about 1.5 × as long as broad and clearly shorter than palpomere 3 (in Tohlezkus pipe-shaped or weakly clavate, 2–3 × as long as broad and clearly longer than palpomere 3); (4) maxillary palpomere 4 almost gradually narrowing distally (in Tohlezkus rapidly narrowing so that apical region forms a nearly rod-like projection); (5) postcoxal carina on metaventrite at middle straight (in Tohlezkus forming subtriangular expansion between mesocoxae projecting anteriorly); (6) median region of metaventrite broadly subtriangular, in posterior half forming a nearly equilateral triangle (in Tohlezkus median region of metaventrite has strongly concave sides, so that its anterior region is broad but posterior very narrow, nearly needle-shaped, posterior half forming strongly elongate triangle with narrowly sharp posterior apical angle); (7) apical mesotibial spurs of subequal lengths and both subparallel up to rounded apices (in Tohlezkus mesotibial spurs are of strongly unequal lengths and both narrowing from bases to pointed apices).

Figures

FIGURES 1‒4. Dorsal habitus of males. Bisayodes hure gen. & sp. n. (1); Tohlezkus uminchu sp. n. (2); Tohlezkus orientalis Vít (3); Tohlezkus rufus (M. Sakai) (4).

FIGURES 5‒6. Bisayodes hure gen. & sp. n. Dorsal (5) and ventral (6) habitus.

FIGURES 7‒12. Bisayodes hure gen. & sp. n. Head in dorsal (7, 11), ventral (8, 12) and anteroventral (9) views; right antenna in anteroventral view (10).

FIGURES 13‒19. Bisayodes hure gen. & sp. n. Labrum in dorsal view (13); mandible in dorsal view (14); right maxilla in dorsal (15) and ventral (16, 17) views; labium (excl. submentum) in ventral view (18); mentum, prelabium and maxilla in ventral view (19).

FIGURES 20‒22. Bisayodes hure gen. & sp. n. Pterothorax in ventral view (20); fore femur, tibia and tarsus in ventral view (21); left mesotarsus and apex of mesotibia in ventral view (22).

FIGURES 37‒40. Aedeagus. Bisayodes hure gen. & sp. n. (37); Tohlezkus uminchu sp. n. (38); Tohlezkus orientalis Vít (39); Tohlezkus rufus (M. Sakai) (40).