Bioacoustics of Xystodesmus kumamotoensis

Description. Length 26–27 mm , midbody width with paraterga 4.8–5.0 mm, midbody metatergal length 1.2–1.3 mm , collum width 3.8–3.9 mm , median collum length 1.9 mm . Body sides between segments 5–16 subparallel. Head smooth, with two frontal setae, epicranial suture distinct. Antennal articles straight, slender, first article short, 1.5 × longer than wide, articles 2–6 subequal in length, 7 small, with length equal to width. Proterga completely smooth, metaterga weakly wrinkled, each with a shallow transverse depression in the middle. Collum subtrapezoid-shape, arched, 1.5 × longer than metatergum 2, lateral edges directed posterioventrad, anteriolateral margin with well visible ridge. Posterior edge of paranota 2–5 rounded, triangular projection only starts from segment 6 onwards, posterior margin of each metaterga straight, sublateral excavations hardly detectable. Lateral sides of paranota straight, almost giving a parallel straight outline to the body. Pore formula normal, pores in lateral position on narrow paranota. Segments 17–19 gradually tapering, posteriolateral corners becoming more pointed. Epiproct protruding, in lateral view slightly curved, with two pairs of setae on small side tubercles, and with two setae apically; paraprocts smooth, with two pair of setae on obvious median ridges; hypoproct subtriangular. Bases of midbody leg pairs clearly separated (by 1.1 mm ), sterna smooth and wide, pro- and metasterna also clearly separated. Postgonopodal prefemora with well-developed ventral spine, increasingly larger from midbody legs onwards, femur 1.5 × longer than prefemur, slightly bent proximad, postfemur short and curved, tibia slender, tarsus 1.5 × longer than tibia, claws normal on all legs. Colour of living specimens unknown. Preserved specimens show faded pattern typical for Xystodesmus : metaterga slightly darker, proterga paler, paranota with pale orangish / yellowish spot. Clypeus light brownish, underside of head, antennae, legs, epiproct, and whole ventral side light pale white. Male sexual characters . Second leg pair with tubulous coxal processes (Fig. 3 D ), densely setose. Sterna of segments 4 and 5 (Fig. 4 A, B ) with a pair of protruding processes, on segment 4 longer, pointed, without setae, on segment 5 lower, widely separated from each other, without setae. Other legs and sterna without modifications. Gonopods (Fig. 3 A – C ): Coxa short and thick, almost as wide as long, no trace of apophyseal process, only a strong single seta ( ms ) on the anteriomesal side. Prefemur stout, nearly straight, densely setose, prefemoral process ( pfp ) broad and flat, lamellate, ~ 2 × as song as wide, subrectangular from ventral view, distal margin slightly serrated (Fig. 3 B ). Acropodite ( a ) delimitated from prefemur by a weak constriction, its length only a little longer than prefemoral process, and soon divided into two branches subequal in length, directed anteriorly and gradually tapering to their pointed tips. Prostatic groove runs to the tip of the branch situated laterad, which is also provided with a small tooth (Fig. 3 B , t ) on it lateral side, best visible in situ from direct ventral view. Female sexual characters . Cyphopods (Fig. 4 C ) situated in deep, joint excavation behind leg pair 2, loosely encapsulated in vulval sacs, well separated from each other. Receptacles ( r ) both on anterior and posterior side, densely setose; operculum ( op ) situated laterally, small, rounded, with numerous short setae; valves ( v ) hairless, mesally with conspicuous pointed apices, closely parallel to each other.