Laccobius (Cyclolaccobius) martini, Jia, Fenglong, Song, Keqing & Gentili, Elio, 2013

Jia, Fenglong, Song, Keqing & Gentili, Elio, 2013, A new species of Laccobius Erichson, 1837 from China (Coleoptera: Hydrophilidae), Zootaxa 3734 (1), pp. 91-95 : 92-95

Laccobius (Cyclolaccobius) martini sp. nov.

( Figs. 1–9 )

Type locality. China, Guangxi, Shiwandashan Mts., 2189900˚N, 107.90570˚E.

Type material. Holotype: ♂ (SYSU): China: Guangxi, Shiwandashan Mt., in the upper part of Shitouhe River (=Stone River), Tri-channel river, in sands of water margin among large stones, 21.89900˚N, 107.90570˚E, 339 m a.s.l., 9.vii. 2011, Keqing Song leg. (with Chinese and English labels). Paratypes: 12 ♂♂, 9♀♀ (SYSU, MSNV, IZCAS): same data as holotype.

Differential diagnosis. Laccobius martini sp. nov. is very close to L. hainanensis Jia, Gentili & Fikáček, 2013 , but can be distinguished from it by the whole dorsal surface with white setae (yellowish brown setae in L. hainanensis ), the setae forming 10 white lines along primary punctural rows (specify the state of this character in L. hainanensis here), secondary rows of punctures somewhat sparser, and the median lobe of aedeagus not constricted subapically (constricted subapically in L. hainanensis ). The new species can be distinguished from L. politus Gentili, 1979 , another similar species, by the wider lateral pale stripe on elytra suddenly widening near the elytral apex (more or less uniformly wide in L. politus ), the elytral puncture rows more conspicuous (scarcely evident in L. politus ), the primary rows with dense and conspicuous white setae that form 10 lines along primary punctural rows (setae inconspicuous or barely conspicuous in L. politus ), and parameres wider than median lobe (parameres narrower in L. politus ).

Description. Total length 1.8–2.1 mm (holotype 2.0 mm); maximum width 1.3–1.4 mm (holotype 1.3 mm). Total length / total width ratio = 1.5. Body oval, moderately convex, with greatest width in anterior third of elytra, evenly narrowed posteriad ( Fig. 1 ).

Head. Labrum black, without specula in both sexes, slightly convex on anterior margin, closely adhering to clypeus; surface densely punctured, anteriorly with stiff white setae. Clypeus and frons shiny black, preocular pale spots extremely small and vague or completely absent ( Fig. 3 ); surface with irregular, sparsely arranged fine punctures, punctures slightly impressed but larger than labral punctures, each puncture with decumbent white seta; microsculpture absent. Clypeus nearly 1.5× as wide as long, deeply emarginate anteriorly; frontoclypeal suture scarcely apparent. Eyes transversely oblique, nearly 2.5× as large as long, reniform posteriorly ( Fig. 3 ), closer to each other posteriorly than anteriorly; minimum interocular distance in frontal view 2.3× of width of one eye. Ventral surface black, except the brown maxillae. Mentum flat, uniformly microreticulated, with sparse punctures. Postmentum smooth, gula granulate. Maxillary palpi yellowish; palpomere 3 inflated, palpomere 4 asymmetrical, straight medially and convex laterally, scarcely infuscate at extreme apex. Labial palpi same colour as maxillary palpi. Antennae with 8 antennomeres, yellowish with darker club; scape (antennomere 1) longer than antennomeres 2–4 combined, pedicel (antennomere 2) cone-shaped, two intermediate antennomeres (antennomeres 3–4) very short, cupule (antennomere 5) asymmetrical, oval ventrad, crescent-shaped and emarginated dorsad, antennomere 7 expanded, larger than remaining club antennomeres, antennomere 8 constricted near apex.

Thorax. Pronotum black with green reflection, laterally with a sinuate yellowish irregular band widening posteriorly ( Fig. 3 ), external borders slightly explanate; microsculpture absent, punctation consisting of fine sparsely arranged white-setiferous punctures, only with irregular serial arrangement of punctures along margins. Prosternum with narrow longitudinal carina medially. Scutellar shield equilaterally triangular, black with strong green reflection, with a few punctures. Mesoventrite with longitudinal keel, anteriorly forming a “beak”. Elytra combined ca. as long as wide (i.e., elytral index = 1.0), black on disc, yellowish along lateral margins, lateral pale stripe slightly widening anteriorly, more widening posteriorly, very narrow at midlength. Elytral punctation consisting of fine setiferous punctures (each bearing a white seta) arranged in ca. twenty longitudinal rows, with alternating series of larger and denser punctures (primary rows) and more irregularly and sparsely distributed finer punctures (secondary rows), the setae forming 10 white lines along primary punctural rows ( Figs. 1–2 ). Parasutural furrow absent. Microsculpture absent. Lateral margins of elytra slightly explanate with a narrow bead. Epipleura ending at level of metafemora. Metaventrite with decumbent pubescence ( Fig. 4 ), which is absent from a small medioposterior area.

Legs. Coxae dark brown, trochanters and other segments of legs yellowish brown. Trochanters with sparse pubescence, apical part of metatrochanter not abutted to femur. Femora pubescent basally, metafemur with coarser setiferous punctures. Tibiae with rows of spines more developed on outer margin and on mesotibiae, metatibiae curved. Tarsal natatory setae nearly absent. Legs with five tarsomeres; protarsomere 5 nearly 3× as long as other protarsomeres; mesotarsomeres 2 and 5 each nearly 2× as long as other mesotarsomeres; metatarsomeres 1 and 2 each longer than other metatarsomeres. Claws shorter than tarsomere 5, arcuate. Male with basal 2 protarsomeres dilated.

Abdomen. Ventrites nearly smooth, sparsely pubescent, covered with broken-glass-like material; ventrite 5 and 6 wrinkled, pubescence denser on ventrite 6 than on ventrites 1–5.

Aedeagus. Total length 0.42 mm. Parameres nearly 1.9x as long as phallobase. Phallobase 1.2x as long as wide ( Figs. 5–6 ). Parameres slightly narrowing from base to apex, lateral and medial margins very slightly arcuate; distance between lateral margins of phallobase almost as wide as distance between lateral margins of parameres; apex of parameres asymmetrical, obtusely pointed. Median lobe as long as parameres, conically narrowing from base to midlength, then almost parallel, conspicuously narrowing apically. Sternite 9 as in Fig. 7 .

Etymology. Named in honour of Dr. Martin Fikáček, Department of Entomology, National Museum, Czech Republic, and Department of Zoology, Faculty of Science, Charles University in Prague, a hydrophilid specialist who has collaborated with the first and third authors many times.

Biology. All known specimens were collected in an aquatic situation, living underwater in the sand at a river edge ( Figs. 8–9 ). When the sand underwater is stirred, the beetles float up to water’s surface and swim on the surface or swim down quickly. When they reach the substrate, they immediately walk downwards and hide beneath it.

Remarks. The key to Chinese species of the subgenus Cyclolaccobius (Jia et al. 2013) may be modified as following:

5a. Dorsum with white setae, the setae forming 10 white lines along primary punctural rows, secondary rows of punctures somewhat sparser............................................................................ L. martini sp. nov.

- Dorsum with yellowish brown setae or without conspicuous setae, the setae not forming lines along primary punctural rows, secondary rows of punctures somewhat denser............................................................. 5b 5b. Elytral primary puncture rows conspicuously setiferous at 100×; fifth row slightly sulciform. Elytral pale lateral strip constricted at midlength, then suddenly widening near elytral apex. Median lobe constricted subapically, weakly narrowing apicad.............................................................. L. hainanensis Jia, Gentili & Fikáček, 2013 - Elytral primary puncture rows not or scarcely setiferous at 100×; fifth row normal, not sulciform. Elytral pale lateral strip uniformly wide, only widening near elytral apex. Median lobe indistinctly constricted subapically, widely rounded at apex........................................................................................ L. politus Gentili, 1979

Figures

FIGURES 1 – 7. Habitus and details of Laccobius martini sp. nov. 1) dorsal habitus; 2) lateral habitus; 3) head and pronotum, laterally; 4) meso- and metasternum; 5) aedeagus, dorsal view; 6) same, lateral view; 7) sternite 9.

FIGURES 8 – 9. Habitat of Laccobius martini sp. nov. 8. General view of the river where the type specimens of the new species were collected; 9. Collection site of the type specimens of the new species (pointed with arrow).