Omicrogiton hainanensis, 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 : 102-104

Taxon classification Animalia Coleoptera Hydrophilidae

Omicrogiton hainanensis sp. n. Fig. 15

Type material.

Holotype: male (SYSU): CHINA: Hainan Isl.: Limushan Mts., 19°9.1-9.2'N, 109°45-46'N, along the road, 550-750 m a.s.l., rotting banana trunks at the stream in secondary forest, 5.v.2011, Fikáček & Zhao lgt. Paratypes: 2 males (SYSU, NMPC): same locality as the holotype; 2 males (NMPC): China: Hainan Isl.: Jianfengling Mts., Tiachi Lake env., Bishu villa, rotting banana trunk at the bank of a drying-up stream in the primary forest above the hotel area, 18°44.7'N 108°50.7'E, 950 m a.s.l., 9-11.v.2011, Fikáček, Kubeček & Li lgt.

Diagnosis.

Body length 1.9-2.0 mm. Head and elytra brown; scapus ca. 3.5 × as long as antennomeres 2-5 combined. Interstices of pronotum without microsculpture; prosternum weakly tectiform. Phallobase ca. as long as parameres, wide anteriorly, with wide rounded manubrium; paramere with strongly sclerotized S-shaped portion and membranous mesal and apical portions, sclerotized parts of left and right paramere forming very obtuse angle basally; median lobe narrower than phallobase and paramere, rather wide basally, gradually narrowing towards apex, apex rather widely rounded, gonopore subapical (Fig. 15).

Description.

Form and Color. Body oval, weakly convex, length 1.9-2.0 mm, width 1.2 mm. Head, pronotum and elytra brown; lateral margin of elytra paler than disc; labrum, maxillary palpomeres and antennomeres 1-6 reddish brown, antennal club of antennae slightly paler; ventral surface brown, legs reddish brown.

Head. Clypeus with fine punctures, interstices without microsculpture; lateral deflexed extensions not defined from clypeal disc by ridge; anterior margin with narrow marginal bead laterally. Frontoclypeal suture undetectable. Frons with sparser and coarser punctures than on clypeus, interstices without microsculpture. Eyes small, clearly protruding, interocular distance ca. 5 × as wide as one eye in dorsal view. Labrum exposed, sinuate on anterior margin. Mentum dull, densely granulate, without punctures, ca. 2 × as wide as long, not depressed anteromedially, anterior margin slightly protruding medially. Submentum declined below the level of mentum. Antenna with 9 antennomeres, scapus ca. 3.5 × as long as antennomeres 2-5 combined, club compact, last club antennomere the widest. Maxillary palpomere 2 moderately swollen, palpomere 4 almost symmetrical, widest at midlength, equal in length to palpomere 2, 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 weakly tectiform; antennal grooves absent. Mesoventrite strongly and abruptly raised medially to form a narrow longitudinal lamina not reaching metaventral process posteriorly; cavities for reception of procoxae absent. Metaventrite weakly convex, without glabrous median portion, with weak 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 those on pronotum, interstices without microsculpture; humeral bulge absent; lateral margin of elytron 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 coarse 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 ca. as long as first metatarsomere. First metatarsomere almost as long as metatarsomeres 2-3 combined.

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

Male genitalia. Phallobase ca. as long as parameres, wide anteriorly, with wide rounded manubrium; paramere with strongly sclerotized S-shaped portion and membranous mesal and apical portions, membranous apex of paramere widely rounded; sclerotized parts of left and right paramere forming very obtuse angle basally; median lobe narrower than phallobase and paramere, wide basally, gradually narrowing apicad, apex rather widely rounded, gonopore subapical (Fig. 15).

Differential diagnosis.

Omicrogiton hainanensis sp. n. belongs to the species with strongly sclerotized S-shaped portion of the paramere, together with the Oriental Omicrogiton insularis Orchymont, 1919 and Omicrogiton gomyi Bameul, 1986 from the Reunion Island ( Bameul 1986). It differs from Omicrogiton insularis by the much wider aedeagus (aedeagus is generally very narrow in Omicrogiton insularis (Fig. 19), much wider parameres with bases of strongly sclerotized parts forming a very obtuse angle (parameres are narrow and bases of sclerotized portions form acute angle in Omicrogiton insularis ) and wide median lobe with subapical gonopore (median lobe is extremely narrow apically and the gonopore is situated at midlength in Omicrogiton insularis ). The aedeagus of Omicrogiton gomyi is similar to that of Omicrogiton hainanensis in the proportions (i.e., it is wide and robust in both species), but Omicrogiton gomyi easily differs by wide median lobe with apical gonopore. Omicrogiton coomani and Omicrogiton roberti , differ from all above species including Omicrogiton hainanensis in parameres lacking the strongly sclerotized S-shaped portion, and Omicrogiton coomani and Omicrogiton cheesmanae may be distinguished from other species including Omicrogiton hainanensis by the pronotum with fine mesh-like microsculpture.

Etymology.

The species name is patronymic, referring to the Hainan Island where this species is commonly collected.

Biology.

All type specimens were collected in decaying banana trunks in primary or secondary rainforests. On the type locality, the specimens of this species were collected in the same banana trunk as two other Omicrogiton species occurring in Hainan (i.e. Omicrogiton roberti sp. n. and Omicrogiton coomani ), which indicates that multiple species may occur syntopically in this genus. For this reason, we excluded females from the type series of this species.

Distribution.

China (Hainan).