Oosternum gibbicolle, Hebauer, Martin Fiká Č Ek Franz & Hansen, Michael, 2009

Hebauer, Martin Fiká Č Ek Franz & Hansen, Michael, 2009, Taxonomic revision of New World species of the genus Oosternum Sharp (Coleoptera: Hydrophilidae: Sphaeridiinae) I. Definition of species groups and revision of the Oosternum aequinoctiale group, Zootaxa 2054, pp. 1-37 : 26-30

Oosternum gibbicolle sp. n.

( Figs. 33 , 40, 44, 52–53, 62, 68, 74, 84)

Type locality: Ecuador, Sucumbíos province, Limoncocha, 250 m a.s.l.

Type material: Holotype. 1 male ( CNC): “ ECU. Napo, 250m / Limoncocha, St. / J. Peck, 25. VI. / 1976, Ber. 355 / forest litter // HOLOTYPE / Oosternum gibbicolle / M. Hansen”. Paratypes (50). ECUADOR: 1 male, 7 unsexed specimens ( CNC, NMPC, ZMUC): “ ECU. Napo, 250m / Limoncocha, 18. / VI. 1976 Ber./ 348, S&J Peck”; 1 unsexed specimen ( CNC): “ ECU. Napo, 250m / Limoncocha, S&J. / Peck, 21.VI.76 / Berlese 351 // nuts & debris / at base of / spiny palm”; 1 unsexed specimen ( ZMUC): “ ECU. Pasteza [sic!], 900 / m. 22Km. SW Puyo / 15.VII.76, Ber. / 362, S&J Peck / litter”; 1 unsexed specimens ( FMNH): “ ECUADOR: Pastaza Prov. / 1000 m. (25 Km N Puyo) / LEG: S. Peck / VII:13:1976 // FM(HD)#76-128 / Ber. #361 / Cloud forest litter”. PANAMA: 1 male, 3 unsexed specimens ( KSEM): “ PANAMA: DARIEN / Estacion Ambiental Cana / 07°45.32΄N 77°41.07΄W / Cerro Pirre, 1300m, 6.VI.1996 / R. S. Anderson, 96-113 / cloud forest trans. litter”; 30 unsexed specimens ( BMNH, HHFU, NHMW, SRBC, ZMUC): “ PANAMA: Darien, Estacion / Ambiental Cana, Cerro Pirre / 1300m, 7°45.32΄N 77°44.07΄W / 6.Jun.1996 R. Anderson / cloud for. trans. lit. 96-113”; 1 male, 3 unsexed specimens ( FMNH, NMPC): “ PANAMA: Canal Zone / Barro Colorado Is. / February 27. 1976 / A. Newton // litter under / old tree and / vine fall”¨; 1 male ( FMNH): “Barro Colorado / Is. CANAL ZONE / July II 1969 // J. F. Lawrence / Lot 2850 // Polyporus / trichomallus”.

Differential diagnosis: Body widest at junction of pronotum and elytra; pronotum highly convex; pronotal punctation dense, consisting of sharply impressed ring-like punctures; pronotal interstices lacking microsculpture; median carina of prosternum without anterior tooth; preepisternal elevation of mesothorax 1.8× longer than wide; median portion of metaventrite without intersticial microsculpture; eyes large, separated by 6.0× width of one eye; parameres without inner projections; lateral projections of median lobe narrow, developed in apical 0.45 of median lobe.

Habitually and by pronotum without intersticial microsculpture, the species is rather similar to O. acutheca and O. attenuatum . From these species as well as from all remaining species of O. aequinoctiale species group it can be easily recognized by ring-like punctures on pronotum (Figs. 52–53).

Description: HABITUS: Body widely oval, widest on base of elytra, highly convex in lateral view, strongly narrowing posteriad; TL/TW ratio = 1.55. Length: 1.20–1.35 mm, length of HT: 1.20 mm; width: 0.75–0.95 mm, width of HT: 0.75 mm.

COLORATION. Coloration of dorsal side dark brown, anterior margin of clypeus, lateral margins of pronotum and lateral margins of elytra reddish. Ventral side reddish brown. Coxae, femora and tibiae pale reddish, tarsi, mouthparts and antennae yellowish, antennal club brown.

HEAD. Clypeus with dense punctation consisting of fine, sharply impressed round punctures, each puncture bearing fine decumbent yellowish seta; interstices without microsculpture; anterior margin truncate. Frons with moderately dense punctation consisting of small, sharply impressed round punctures, punctures of same shape medially and laterally; interstices without microsculpture. Eyes moderately large, separated by 6.0× of width of one eye. Mentum 2.1× wider than long, anterior margin deeply emarginate; punctation consisting of small, sharply impressed round punctures bearing minute setae; interstices without distinct microsculpture. Submentum with poriferous disc-like ereas. Maxillary palpus with palpomeres 2 and 4 ca.

2.0× longer than palpomere 3. Scapus shorter than antennomeres 2–6 combined; antennal club ca. 2.0× longer than wide.

PROTHORAX. Pronotum apparently more convex than elytra in lateral view, punctation consisting of small, sharply impressed, ring-like punctures, similar on whole surface of pronotum; interstices without microsculpture. Median carina of prosternum straight in lateral view. Median portion of prosternum 1.5× wider than long, postero-mesal projection without notch, pits laying next to ridges delimiting prosternal plate minute.

FIGURES 66–71. Prosternal plate. 66: O. acutheca ; 67: O. attenuatum ; 68: O. gibbicolle ; 69: O. latum ; 70: O. aequinoctiale ; 71: O. holosericeum .

FIGURES 72–77. Meso- and metaventrite. 72: O. acutheca ; 73: O. attenuatum ; 74: O. gibbicolle ; 75: O. latum ; 76: O. aequinoctiale ; 77: O. holosericeum .

MESOTHORAX. Scutellar shield bearing few small punctures, interstices without microsculpture. Elytral series 1–5 arising basally, series 6 arising subbasally, series 7 and 8 only reaching anterior 0.4 of elytra, series 9 abbreviated anteriorly, undetectable in ca. basal 0.2. Elytral series 7 and 8 markedly closer to each other than to other series. Serial punctures minute, indistinct under binocular microscope. Elytral intervals moderately convex at suture; intervals 5, 7 and 9 distinctly higher than adjacent intervals; punctation irregular on all intervals, consisting of sparsely distributed, fine, round punctures. Elytral interstices shiny, without microsculpture. Epipleuron narrowing posteriad, reaching elytral apex. Preepisternal plate drop-like, 1.8× longer than wide; median part concave, bearing densely arranged, moderately large setiferous punctures; interstices without microsculpture.

METATHORAX. Punctation of median portion of metaventrite fine and sparse, consisting of semicircular scar-like setiferous punctures, interstices without microsculpture, shiny. Anepisternum 6.6 ×longer than wide.

LEGS. Tarsi with long yellowish pubescence ventrally.

ABDOMEN. Ventrite 1 without additional longitudinal ridges laterally.

MALE GENITALIA. Paramere 1.3× longer than phallobase, without inner projection, bearing two long setae apically. Phallobase narrow, 1.6× longer than wide. Median lobe narrowing from base towards apex; lateral projections narrow, developed in apical 0.5 of median lobe.

Variation: The species varies slightly in size and coloration, as well as in the density of pronotal punctation (sometimes it is slightly denser than in Figs. 52–53). Shape of pronotal punctures and morphology of male genitalia are constant in all examined specimens.

Etymology. Latin gibbus = hump, collum = neck, pronotum. The name was used for this species by M. Hansen in his original manuscript and refers to the highly convex pronotum of this species.

Habitat. All examined specimens were sifted from leaf litter in tropical forests. One specimen was found in nuts and debris under a spiny palm.

Distribution. Distributed along northern part of Andes Mts. at altitudes 250–1300 m a.s.l. Known from Ecuador (Sucumbíos and Morona-Santiago Provinces) and Panama ( Panama and Darien Province).

Figures

FIGURES 32 – 35. Habitus of the representatives of O. aequinoctiale group. 32: O. aequinoctiale; 33: O. gibbicolle; 34: O. holosericeum; 35: O. latum.