Diochus pulchellus Cameron , 1918

Zhou, Yu-Lingzi & Zhou, Hong-Zhang, 2016, Taxonomy of the genus Diochus Erichson, 1839 (Coleoptera: Staphylinidae, Staphylininae, Diochini) in China with descriptions of four new species, Zootaxa 4127 (1), pp. 1-30 : 26-29

8. Diochus pulchellus Cameron, 1918

( Fig. 3 G; Fig. 10 A–N; Fig. 10-1 A–H)

Cameron, 1918: 84 (Type locality: Singapore: Sembawang); Cameron, 1921: 404 ( Singapore); Scheerpeltz, 1933: 1324 (catalog); Herman, 2001: 2448 (catalog); Smetana, 2004 (Palaearctic catalog; Hongkong); Löbl & Löbl, 2015: 1007 (Palaearctic catalog; Hongkong).

Type material examined: male, with labels as follows: “Holo-, Type ”/“ TYPE ”/ “HOLOTYTYPE, Diochus , pulchellus, Cameron, 1918 , det. R.G. Booth 2013”/ “Sembawang, Singapore., Dr. Cameron.”/ “Debris”/ “M. Cameron., Bequest., B.M.1955–147.” ( BMNH).

Description. Measurement. BL= 2.94 mm, FL= 1.61 mm, HL= 0.48 mm, HW= 0.40 mm, PL= 0.52 mm, PW= 0.53 mm, EL= 0.57 mm, EW= 0.70 mm.

Body nearly fusiform shaped, small sized ( Fig. 3 G). Body yellow brown; head, basal half of elytra and abdomen darker. Legs, antennae, maxillary and labial palpi yellow brown.

Head ( Fig. 10 A, D). Rounded triangular in shape (HL to HW ratio 1.2), tempora (behind eyes) gradually dilated and arcuate posteriad, widest at basal 1/5, posterior angles rounded. Dorsal integument shiny, extensively bearing microstriae, but with some polygonal reticulum on frontal region, also with 3–5 small, scattered punctures behind each eye, and numerous smaller punctures on deflexed portion of tempus and near the posterior margin. Each side of cranium with large characteristic punctures: one frontal puncture on frontal region, two anterolateral punctures near antennal insertion, three ocular punctures near dorsal margin of eye, temporal puncture at the basal 1/6, also with occipital puncture near hind margin. Frontal furrows and anteocular furrows absent, with big and round elevation between eyes. Eye large sized, longer than half the length of tempora (eye: tempora = 0.13: 0.20 mm), distinctly protruding laterad. Epistoma not flattened, abruptly oblique, anterior margin emarginate medially. Distance between antennal insertions 0.15 mm being distinctly longer than distance from antenna to eye (0.06 mm). Ventral surface ( Fig. 10 D) with scattered punctures, interspaces between them ca. 5 punctures’ diameter. Gular sutures deep, confluent at base 1/3.

Antennae ( Fig. 10 F). Total length 1.00 mm. Scape rod-shaped, slightly thickened apically, 0.19 mm, shorter than two subsequent antennomeres combined; antennomere II elongate, 0.08 mm; III 0.09 mm, slightly longer than II; IV 0.08 mm, longer than V; VI–X subequal in length of 0.06 mm; XI 0.11 mm, longer than X.

Mouthparts ( Fig. 10 G–I). Labrum semi-circle shaped ( Fig. 10 G), lateral margin slightly waved. Mandibles falciform, left one with one or two indistinct teeth on inner edge, right one with one sharper distinct tooth ( Fig. 10 I–J).

Neck ( Fig. 10 J–K). Surface shiny, only bearing shallow microsculpture, in trapezoidal shape, width of 0.15 mm, slightly wider than 1/3 width of head, with a shallow bisinuate basal furrow near posterior margin ( Fig. 4 J). Ventral surface with observable gular sutures, not forming obvious triangular region, which missing transverse median furrow ( Fig. 4 K).

Prothorax ( Fig. 10 B, E). Pronotum elliptical (PL to PW ratio 0.98), with subequal length to head, but distinctly wider. Anterior region near anterior angles not deflexed or not narrowed, lateral margins parallel, anterior and posterior angles broadly rounded. Dorsal surface glossy extensively with micropunctures, but without any microsculpture. Each side of the midline with symmetrical five large lateral punctures, with additional 13–15 punctures near each margins (including anterior, lateral and posterior margins). Prosternum bearing observable transverse ridge between basisternum and furcasternum, which angularly backwards ( Fig. 10 E).

Pterothorax. Mesoscutellum triangular and small ( Fig. 10 M). Surface shiny, bearing some light microstriae, but without any punctures. The transverse ridge on mesoventrites in wave shape; the paired oblique furrows short but deep; the carina (limiting mesocoxal cavity) slightly arcuate. The discrimen region on metaventrite normally elevated.

Elytra ( Fig. 10 C). Transverse and short (EL to EW ratio 0.81), longer than pronotum, and distinctly wider. Humeri well developed, lateral margins divergent posteriorly, hind margin not rounded, but obliquely truncate. Dorsal integument shiny, flattened, without microsculpture; each elytron with a row of 5 punctures along suture, a row of 5 punctures in median, also with 4–5 rows of punctures on deflexed portion.

Legs ( Fig. 10 L). First four segments of protarsi not dilated, as wide as those of meso- and metatarsi. Last segment of protarsi as long as II and III together; that of mesotarsi slightly longer than II and III together; that of meta- longer than II and III together.

Abdomen ( Fig. 10 N). Broadest at segment V. Tergites III–VII covered with dense and obvious transverse microstriae; each tergite with dense yellow pubescence, also with a row of darker and coarser setae at posterior margin of III–VI. Tergites III–VII with a basal impression near anterior margin, respectively, each one only possessing one basal transverse carina; surface shiny, bearing polygonal reticulum, but without any punctures. The intersegmental membrane bearing transparent yellow fenestra. All abdominal sternites shiny, with microstriae and punctures as those on tergites.

Male ( Fig. 10-1 A–H). Posterior margin of tergite VIII arcuate ( Fig. 10-1 A), that of sternite VIII bisinuate ( Fig. 10-1 B). Tergite IX symmetrical, connected mediobasally ( Fig. 10-1 C), sharpened apically. Sternite IX symmetrical, widest near the middle, without longitudinal furrow near each lateral margin, and basal margin concaved ( Fig. 10-1 D). Tergite X symmetrical, large with arcuate posterior margin ( Fig. 10-1 C). Aedeagus pearlike shaped and symmetrical ( Fig. 10-1 E–G), small sized, ca. 0.31 mm long. Parameres long and symmetrical, slightly curved apically, 4/5 times the length of basal bulb. Internal sac possessing inner sclerites, sperm pump coiled once, not thinned toward apex ( Fig. 10-1 H).

Female. Unknown.

Distribution. China ( Hongkong); Singapore.

Remarks. This species is distinguished from its congeners by the combination of the following characters: 1) the rounded labrum; 2) the blunt teeth on left mandible; 3) emarginated posterior margin of abdominal sternite VIII; 4) slender and elongate parameres and apical broad sclerites of aedeagus.

Figures

FIGURE 3. Habitus of seven species in dorsal view: A. Diochus japonicus Cameron, 1930; B. D. bicornutus sp. nov.; C. D. conicollis (Motschulsky, 1858); D. D. ampullaceus sp. nov.; E. D. bisegmentatus sp. nov.; F. D. membranaceus sp. nov.; G. D. pulchellus Cameron, 1918. Scale bars 0.50 mm.

FIGURE 4. Diochus bicornutus sp. nov.: A. head, dorsal view; B. pronotum, dorsal view; C. elytra, dorsal view; D. head, ventral view; E. pronotum, ventral view; F. elytra, ventral view; G. antennae; H. labrum; I. left mandible; J. right mandible; K. neck, dorsal view; L. neck & cervical sclerites, ventral view; M. proleg; N. mesoscutellum; O. basal visiable four segments of abdomen, dorsal view; P. labial & maxillary palpi, ventral view. Scale bars 0.30 mm.

FIGURE 10. Diochus pulchellus Cameron, 1918: A. head, dorsal view; B. pronotum, dorsal view; C. elytra, dorsal view; D. head, ventral view; E. pronotum, ventral view; F. antennae; G. labrum; H. left mandible; I. right mandible; J. neck, dorsal view; K. neck; L. proleg; M. mesoscutellum; N. basal visiable four segments of abdomen, dorsal view. Scale bars 0.30 mm.