Hemiosus ater, Clarkson, Bruno & Ferreira-Jr, Nelson, 2009

Clarkson, Bruno & Ferreira-Jr, Nelson, 2009, Three new species of Hemiosus Sharp (Coleoptera: Hydrophilidae) and new state records of Hemiosus fittkaui Oliva and H. moreirai d’Orchymont from Brazil, Zootaxa 2139, pp. 61-68 : 62-64

Hemiosus ater , sp. nov.

(Figs. 1–6)

Type Material. Holotype 3, DZRJ: ( Coleoptera 2860 ) “ BRASIL: Rio de Janeiro,/ Nova Friburgo,/ Rio Cascatinha,/ 28.III.1992,/ -22.340408°, -42.557367°,/ J.L. Nessimian leg.”; Paratypes. 1 3, DZRJ: ( Coleoptera 1296 ) “ BRASIL: Rio de Janeiro,/ Nova Friburgo,/ Rio Cascatinha,/ 26.II.1992,/ -22.340408°, - 42.557367°,/ J.L. Nessimian leg.”; 1 3, DZRJ: ( Coleoptera 2862 ) “ BRASIL: Rio de Janeiro,/ Nova Friburgo,/ Rio Cascatinha,/ 25.V.1991,/ -22.340408°, -42.557367°,/ E.R. Silva & L.F.M. Dorville leg.”; 4 Ƥ, DZRJ: ( Coleoptera 2861 ) “ BRASIL: Rio de Janeiro,/ Nova Friburgo,/ Rio Cascatinha,/ 28.III.1992,/ -22.340408°, - 42.557367°,/ J.L. Nessimian leg.”; 1 3, MNRJ: “ BRASIL: Rio de Janeiro,/ Nova Friburgo,/ Rio Cascatinha,/ 28.III.1992,/ -22.340408°, -42.557367°,/ J.L. Nessimian leg.”; 1 3, MNRJ: “ BRASIL: Rio de Janeiro,/ Nova Friburgo,/ Rio Cascatinha,/ 29.IV.1995,/ -22.340408°, -42.557367°,/ folhiço de fundo particulado,/ J.L. Nessimian leg.”; 3 Ƥ, MNRJ: “ BRASIL: Rio de Janeiro,/ Nova Friburgo,/ Rio Cascatinha,/ 28.III.1992,/ - 22.340408°, -42.557367°,/ J.L. Nessimian leg.”; 1 3, MZSP: “ BRASIL: Rio de Janeiro,/ Nova Friburgo,/ Rio Cascatinha,/ 29.IV.1995,/ -22.340408°, -42.557367°,/ folhiço de fundo particulado,/ J.L. Nessimian leg.”; 1 3, MZSP: “ BRASIL: Rio de Janeiro,/ Nova Friburgo,/ Rio Cascatinha,/ 31.VIII.1991,/ -22.340408°, - 42.557367°,/ VIII-Fauna, E.R. Silva & L.F.M. Dorville leg”. 3 Ƥ, MZSP: “ BRASIL: Rio de Janeiro,/ Nova Friburgo,/ Rio Cascatinha,/ 28.III.1992,/ -22.340408°, -42.557367°,/ J.L. Nessimian leg.”

Diagnosis. Dorsal surface almost entirely melanic. Elytra (Fig. 1) each with interstria 9 slightly raised from posterior half of its length to the intersection with interstria 11; interstria 10 strongly raised in anterior part, even under humeral hump; interstria 11 slightly raised. Mesosternal process (Figs. 2, 3) very broad; with strongly raised anterior tooth followed by a shorter tooth and pair of lateral teeth; metasternal process (Fig. 2) wide; anterior carina flat and strongly raised. Ventrite I (Fig. 4) with broad tabular medial carina expanded into round apex; fifth (Fig. 4) ventrite apical notch with short median triangular tooth. Male genitalia (Figs. 5, 6) with median lobe shorter than paramera; appendices acuminate and shorter than median lobe; basal piece approximately same length as distal piece, about twice as long as wide, asymmetrical in basal two-fifths.

Description. Holotype male: total length 4.48 mm; maximum width 2.24 mm; maximum length of the head 1.06 mm; elytral length 3.04 mm; maximum width of the pronotum 1.37 mm.

Dorsal surface melanic. Head and pronotum with metallic sheen. Scutellum without metallic sheen. Elytra with large lighter spot on apical fourth. Apical maxillary palpomeres dark on apical thirds, with light-colored tips. Sternites and legs dark-brown.

Head, pronotum and scutellum punctulate. Head with dense and large punctures; profile flattened; labrum narrow, directed downwards; apical maxillary palpomeres short and thick. Pronotum punctation less dense and finer than head; median line without punctures; posterolateral pits rudimentary; lateral margins depressed and crenulated; anterior angles coarsely crenulated. Elytra (Fig. 1) with punctures much larger than the pronotal ones; scutellar stria developed with deep punctures; inner interstriae wide and flat, about 3 times as wide as striae, with row of very small punctures; outer interstriae narrow and convex; interstria 9 slightly raised from posterior half to intersection with interstria 11; interstria 10 strongly raised in anterior two-thirds, even under humeral hump; interstria 11 slightly raised throughout its length; lateral edge of elytron with deep and very coarse punctures. Mesosternal process (Fig. 2) in ventral view very broad, especially in anterior third, with median depression; in lateral view (Fig. 3) with strongly raised anterior tooth followed by a shorter tooth; pair of lateral teeth on anterior third of process; posterior third raised and slanting posteriorly. Metasternal process (Fig. 2) wide; anterior carina flat and strongly raised, more strongly raised than the mesosternal process; posterior edge of process weakly produced. Legs with middle and hind femora with extensive pubescence, about four-fifths of its length. Ventrite I (Fig. 4) with broad tabular medial carina, expanded into round apex, which overlaps the posterior edge of sternite, raised on anterior part and slanting posteriorly; lateral carinae narrow, flat, broadened posteriorly, about two-thirds the length of sternite. Ventrites II and III with flat basal carinae rounded apically, which do not reach posterior margin of sternites. Ventrite V apical notch with median portion produced in triangular tooth; lateral margins very finely crenulate. Male genitalia (Figs. 5, 6) with median lobe shorter than paramera, subcylindrical and blunt, only tip visible in ventral view; appendices shorter than the median lobe and acuminate; paramera slightly constricted in apical third, tips turned inwardly; basal piece approximately same length as distal piece, about twice as long as wide, asymmetrical in basal two-fifths.

PLATE 1. Figs. 1–6. Hemiosus ater , sp. nov., 1: left elytron in lateral view: colour pattern, interstria 9 and 11 slightly raised, interstria 10 raised under the humeral hump; 2: mesosternal and metasternal process in ventral view; 3: mesosternal process and anterior part of metasternal process in lateral view; 4: apparent ventrites in ventral view: median and lateral carinae, apical notch; 5: male genitalia in ventral view; 6: male genitalia in lateral view. Scale on figs. 1 and 4 = 1.0 mm, others = 0.5 mm.

Etymology. The specific name is derived from the latin ater , meaning black, alluding to the dark, mostly melanic, dorsal surface, which is exceptional in this genus.

Taxonomic notes. The above-mentioned characters can distinguish the new species from all other described Hemiosus . The combination of the genitalia shape and shape of the mesosternal and metasternal processes are diagnostic of this species. The new species is the only species in the genus to have its dorsal surface almost entirely melanic. Among the Neotropical genera of Berosini, all Derallus Sharp and few Berosus Leach species have melanic dorsal surfaces, completely dark in the former or with light areas in the latter. Hemiosus ater , sp. nov., is a large species, considering that other Hemiosus usually measure between 3mm and 4mm. Frequently, in the genus, interstriae 10 and 11 of the elytra are raised for part of their length, but rarely along the anterior half, especially under the humeral hump. Previously, this condition has only been reported for H. moreirai ( Oliva 1991, 1994), and is now described for H. ater , sp. nov., and H. santosi , sp. nov. (see below), in addition both also have interstria 9 slightly more raised than in H. moreirai . Hemiosus moreirai has a wide distribution in Rio de Janeiro state, also occurring in the same stream in Nova Friburgo (Santos et al., In press), where H. ater , sp. nov., was collected.