Ishikawatrechus bidilatatus Sugaya

Sugaya, Kazuki & Yamasako, Junsuke, 2014, A new species of the genus Ishikawatrechus (Coleoptera, Trechinae) from Japan, Zootaxa 3768 (2), pp. 189-195 : 190-194

Ishikawatrechus bidilatatus Sugaya , sp. nov.

( Figs 1–4, 7–8 , 11–15 )

Type series ( EUMJ). Holotype: 1♂, “[ EHIME: JAPAN] / Ôyashiki, Kawano-uchi / Tôon-shi, alt. ca. 530 m / 14. V. 2012 / K. Sugaya leg.” [printed on white label]; “ HOLOTYPE / Ishikawatrechus bidilatatus sp. nov. ” [printed on red label].

Paratypes: 1 ♂, same data as holotype but alt. ca. 630 m, 28. X. 2010, K. Sugaya leg.; 1 ♂, same locality but 16. X. 2011, K. Sugaya leg.; 1 ♀, same locality but 3. XII. 2011, Y. Hara leg.; 1 ♀, same locality as holotype but 6. VII. 2012, K. Sugaya leg.

Description (n = 5). Habitus as in Figs 1–2 .

Coloration in dried specimens almost dark reddish brown, but light reddish brown and translucent when alive; palpi, antennomeres 5–11 and legs lighter than the other body parts; pronotal disc and elytral disc markedly iridescent

Body glabrous; 2 setiferous pores on stria 3 at basal 1/6 and 1/3 respectively; single setiferous pore on stria 5 at basal 3/5.

Head subquadrate, widest before neck, thence slightly narrower anteriorly; HL/HW 1.05–1.10 (1.08); HW/PW 0.68–0.70 (0.69); HL/PL 0.67–0.73 (0.71); genae weakly convex; frontal furrows deep, but gradually getting shallower and indistinct posteriorly; dorsum with deeply impressed microsculptures composed of fine reticulation, and some deep wrinkles on supraorbital area. Eyes almost effaced, with conspicuous remnants which are elongateoblong and weakly convex laterally. Mentum tooth bifid. Approximate ratio of antennomeres of holotype as follows; 1.04: 1.00: 1.83: 1.67: 1.67: 1.63: 1.54: 1.38: 1.38: 1.27: 1.44.

Pronotum elongated subcordate, widest at basal 3/4; PW/HW 1.44–1.46 (1.45), PL/PW 1.02–1.08 (1.05), PA/ PW 0.67–0.70 (0.69), PB/PW 0.61–0.63 (0.62); PB/PA 0.88–0.94 (0.91); front margin shallowly emarginate; sides forming edge, arcuately dilated in apical 1/3, widest at apical 2/5, thence straightly narrowed posteriorly toward middle and subparallel sided at basal half; front angles obtuse and rounded; basal margin almost straight; hind angles sharp, weakly projecting backwards; dorsum convex dorsally in apical 2/3, thence declivous posteriorly, depressed near base; median line deep; apical transverse impression distinct; basal transverse impression wide and deep, longitudinally foveolate on each side of median line, laterally merging into basal foveae, which are deep and widely extended anteriorly along side borders; surface even with vague microsculpture composed of transverse finely engraved lines, radially with distinct waving wrinkles extending from median line. Proepipleuron expanding outwards and visible from above.

Elytra oval, widest at basal half; EW/PW 1.78–2.01 (1.84); EL/PL 2.52–2.62 (2.59); EL/EW 1.35–1.54 (1.48); basal peduncle with deep transverse furrow; prehumeral borders slightly short, oblique, slightly emarginate, diminishing anteriorly but reaching basal carina of intervals 5 and 6; humeri very obtuse; lateral sides hardly emarginate behind humeri; disc depressed basal 1/5 which is delimited by the basal part of interval 5 laterally, thence very convex dorsally, with a depression on each lateral side before middle; striae slightly crenulate, deeply impressed but becoming indistinct outwards gradually; apical striole deep, not connected with any stria but directed to the termination of stria 5; each strial interval slightly convex dorsally; microsculpture composed of transverse finely engraved lines.

Male genitalia (n = 3, Figs 3–4 , 11–15 ). Aedeagus in lateral view ( Fig. 3 ) robust, about 1/3 as long as EL, curved ventrally at basal 1/3, thence hardly arcuate apically; basal part markedly curved ventrally behind basal orifice, roundly pointed at apex, with small sagittal aileron; apical part in dorsal view ( Fig. 4 ) tapered apically, faintly twisted leftwards; apical orifice wide, deeply emarginated at left side; apical lobe in dorsal view ( Fig. 4 ) not so extended forward, with rounded apex; ventral hook elongate. Styli ( Fig. 3 ) in lateral view feebly curved ventrally, bearing 4 setae on each apex; left one obviously larger than right one.

Internal sac in fully inflated condition through eversion (n = 2, Figs 11–14 ) about 1.50 times as long as aedeagus, pyriform, nearly symmetrical though twisted rightwards behind middle; basal half swollen in campanular shape, with two projections on dorsal side and a copulatory piece (CP, Figs 11, 13–15 ) on left side, covered with spicules except for elongated narrow area on basal 1/5 of left latero-ventral side; apical half well swollen in bulb-shape, with spicules on longitudinal area extending from basal half successively to periphery of gonopore through right latero-ventral side; gonopore (GP, Figs 11, 14 ) opening ventral side. Dorsal projections ( Figs. 11–14 ) composed of large and small triangular swellings; large one just before the middle of internal sac, small one before the large one. CP hyaline, elongated paddle-shaped, attached on the middle of right side of internal sac, about 1/5 as long as internal sac, rounded at apex. Spicules ( Figs. 11–15 ) fine, scaly and feebly sclerotized, gradually getting larger and more spinous dorsally; those on apical half rudimentary sclerotized.

Female genitalia (n = 2, Figs 7–8 ). GC1 rectangular, with 4–5 short setae on ventral side of apical margin and 2 short setae on dorsal side of inner margin near apex; GC2 thick, slightly curved outwardly, roundly pointed at apex, weakly emarginated near base on outer margin, with 2 ensiform setae on dorsal side near base and 2 nematiform setae on ventral side near apex.

Measurement (n = 5). TL: 5.34–6.23 (5.75) mm, HL: 0.86–0.99 (0.95) mm, HW: 0.82–0.94(0.88) mm, PL: 1.27–1.45 (1.34) mm, PW: 1.18–1.36 (1.27) mm, PA: 0.82–0.92 (0.88) mm, PB: 0.74–0.84 (0.79) mm, EL: 3.21– 3.79 (3.47) mm, EW: 2.10–2.51 (2.34) mm.

Diagnosis. This new species can be easily distinguished from the other congeners of Ishikawatrechus by its dark coloration and pronotum with subparallel sides at basal 3/7 and short hind angles projected posteriorly. It is similar to I. ishiharai ( Figs 5–6, 9–10 , 16–19 ) in general appearance, but well differentiated from the latter by the following characteristics: large body size, pronotum peculiarly elongated, nearly parallel-sided in basal 3/7; hind angles of pronotum protrudent posteriorly; aedeagus hardly arcuate in apical half; internal sac with two remarkable projections on dorsal side and a copulatory piece on right lateral side.

Etymology. The specific name is referring to the two remarkable dorsal projections on the internal sac.

Biological notes. The type locality is located at the headwaters of a small branch of the Shigenobu River in the northwestern part of Shikoku. All materials in this study were collected from an upper hypogean zone, approximately 100 cm below ground, under a thick layer of volcanic and sedimentary rocks covered with humus.

Remarks. The genus Ishikawatrechus has been divided into 7 species groups based on the combined characteristics of the external features including the male genital structure ( Uéno 1957, 1996, 1999a, 2002, 2008). The new species, I. bidilatatus , should belong to the ishiharai species group (sensu Uéno 1997), which consists of 8 species with 1 subspecies and distributed widely in the Ishizuchi Range ( Uéno 1994, 1997, 1999b, 2008), because of its close relationship with I. ishiharai . The new species shares with I. ishiharai not only external features but also the basic structure of the internal sac, and their type localities are extremely close to each other. On the other hand, in spite of those affinities, I. bidilatatus is well differentiated from I. ishiharai in the structure of the everted internal sac in a fully inflated condition, having appendixes as mentioned in the diagnosis above. The structures of the everted internal sac in a fully inflated condition are therefore valuable characters for the taxonomic study on the genus Ishikawatrechus .

Figures

FIGURES 1 – 2. Habitus of Ishikawatrechus bidilatatus sp. nov., holotype, male. 1, Dorsal view; 2, Left lateral view.

FIGURES 3 – 10. Genital organs of Ishikawatrechus spp. 3 – 4, 7 – 8, I. bidilatatus sp. nov.; 5 – 6, 9 – 10, I. ishiharai. 3, 5, Aedeagus in left lateral view; 4, 6, Apex of aedeagus in dorsal view; 7, 9, Left stylus in ventral view; 8, 10, Ditto in dorsal view. Abbreviations; GC 1, basal gonocoxite 1; GC 2, apical gonocoxite 2.

FIGURES 11 – 19. Internal sac of Ishikawatrechus spp. 11 – 15, I. bidilatatus sp. nov.; 16 – 19, I. ishiharai. 11, 16, Right lateral view; 12, 17, Left lateral view; 13, 18, Dorsal view; 14, 19, Ventral view; 15, Copulatory piece of I. bidilatatus. Abbreviations; CP, copulatory piece; GP, gonopore.