Omicrogiton roberti, Jia, Fenglong, Lin, Renchao, Li, Bijun & Fikacek, Martin, 2015

Jia, Fenglong, Lin, Renchao, Li, Bijun & Fikacek, Martin, 2015, A review of the omicrine genera Omicrogiton, Mircogioton and Peratogonus of China (Coleoptera, Hydrophilidae, Sphaeridiinae), ZooKeys 511, pp. 99-116 : 104-106

Taxon classification Animalia Coleoptera Hydrophilidae

Omicrogiton roberti sp. n. Figs 1, 2, 16

Type material.

Holotype: male (SYSU): CHINA: Hainan isl., Limushan Mts., Limu temple, 5.v.2011, 19°9.1-9.2'N, 109°45-46'E, 550-750 m; along the road, rotting banana trunks at the stream in secondary forest, Fikáček & Zhao lgt.

Diagnosis.

Body length 2.1 mm. Head and elytra black or dark brown; pronotum paler than head and elytra. Scapus ca. 2.5 × as long as antennomeres 2-5 combined. Prosternum strongly tectiform, with low longitudinal carina medially. Phallobase much shorter than parameres, with thin and long basal manubrium; paramere without distinct S-shaped more sclerotized portion, narrow, weakly curved on outer margin, rounded apically; median lobe much broader than paramere, bottle-shaped, widest at basal third, strongly narrowing ca. at midlength, apex broadly truncate; gonopore large, situated subapically (Fig. 16).

Description.

Form and Color. Body oval, weakly convex (Fig. 1), length 2.1 mm, width 1.35 mm. Head and elytra dark brown; pronotum brown; lateral margin of elytra paler than disc; labrum, maxillary palpomeres and antennomeres 1-6 reddish brown, antennal club paler; ventral surface brown, legs reddish brown.

Head. Clypeus with rather densely arranged fine punctures, interstices without microsculpture; lateral deflexed extensions not defined by ridge. Anterior margin of clypeus with narrow bead laterally. Frontoclypeal suture undetectable. Frons with sparser and coarser punctures than on clypeus, without microsculpture on interstices. Eyes small, clearly protruding, interocular distance ca. 7 × as wide as one eye in dorsal view. Labrum exposed, sinuate on anterior margin. Mentum densely granulated, without punctures, ca. 2 × as wide as long, not depressed anteromedially, anterior margin slightly protruding medially. Submentum below the level of mentum. Antenna with 9 antennomeres, scapus ca. 2.5 × as long as antennomeres 2-5 combined, club compact, last club antennomere the widest. Maxillary palpomere 2 moderately swollen, palpomere 4 almost symmetrical, widest in middle, equal to palpomere 2 in length, longer than palpomere 3.

Thorax. Pronotum ca. 2.6 × as wide as long; pronotal punctation similar to that on frons, interstices without microsculpture. Lateral margins with strong bead overlapping to anterior margin, posterior margin of pronotum without bead. Prosternum strongly tectiform, antennal grooves absent. Mesoventrite strongly and abruptly raised medially to form a narrow longitudinal lamina not contacting metaventral process posteriorly, cavities for reception of procoxae absent. Metaventrite weakly convex, with a small glabrous portion, with a posteromedial depression on elevated portion. Elytra widely explanate laterally, with 10 series of large punctures, series 1-5 almost reaching base, series 6-10 abbreviated anteriorly; interval punctures very fine but distinct, similar to on pronotum; interstices without microsculpture. Humeral bulge absent, lateral margin of elytron very finely serrate; epipleuron wide throughout.Profemur glabrous, anterior margin angulate near base, with a large basal depression with golden pubescence, tibial groove sharply defined. Mesofemur with sparse and strong punctures on anterior half, each puncture with a short seta; posterior half glabrous, with fine longitudinal sculpture. Metafemur with fine longitudinal sculpture and scattered fine punctures. Tibiae flat, meso- and metatibiae with long and stout spines along outer face and 1 or 2 pairs of spines on apical half of inner face; metatibial long spur longer than first tarsomere. First metatarsomere almost as long as metatarsomeres 2-3 combined.

Abdomen. Abdomen with five ventrites; first ventrite not longer than ventrites 2-5, without median longitudinal carina; fifth ventrite rounded, not emarginate apically.

Male genitalia. Phallobase much shorter than parameres, with a thin and long basal manubrium. Paramere without S-shaped strongly sclerotized portion, narrow throughout, weakly curved on outer margin, rounded apically. Median lobe much broader than paramere, bottle-shaped, widest in basal third, strongly narrowed ca. at midlength, apex broadly truncate; gonopore large, situated subapically (Fig. 16).

Different diagnosis.

Omicrogiton roberti is similar to Omicrogiton coomani Balfour-Browne, 1939 in the aedeagus without the strongly sclerotized S-shaped portion of the paramere. It differs from Omicrogiton coomani by the morphology of the aedeagus (median lobe very wide with very large subapical gonopore and very short phallobase in Omicrogiton roberti , rather narrow and with small apical gonopore and rather long phallobase in Omicrogiton coomani ) and by the pronotal interstices without fine mesh-like microsculpture (with fine mesh-like microsculpture in Omicrogiton coomani ).

Etymology.

The species is named after Dr. Robert Bagrie Angus, a British specialist on the Helophoridae , who helped us a lot with this study.

Biology.

The holotype was collected in a decaying banana trunk together with specimens of Omicrogiton hainanensis and Omicrogiton coomani .

Distribution.

China (Hainan).