Sacosternum auribleps, Fikáček, Martin & Short, Andrew E. Z., 2010

Fikáček, Martin & Short, Andrew E. Z., 2010, A revision of the Neotropical genus Sacosternum Hansen (Hydrophilidae: Sphaeridiinae: Megasternini), Zootaxa 2538, pp. 1-37 : 8-9

Sacosternum auribleps sp. n.

(Figs. 7–8, 33–34, 41, 43, 50)

Type locality. Brazil, Rondônia State, 62 km SW of Ariquemes near to Fzda. Rancho Grande [ca. 9°58'S 62°48'W; altitude ca. 150 m a.s.l.].

Type material. Holotype: male ( FSCA): “ BRAZIL: Rondônia 62 / km SW Ariquemes, nr / Fzda. Rancho Grande / 3-15-XII-1996 JE Eger / Black Light Trap”. Paratypes (7 spec.): BRAZIL: 2 females, 3 spec. ( FSCA): same data as holotype; 1 male ( KSEM): “ BRAZIL: Rondonia, 62 / km. SW Ariquemes, nr. / Fdza. Rancho Grande / 8-20-XI-1994; J. Eger / C. O'Brien, black light”; 1 male ( NMPC): “ BRAZIL: Rondonia, 62km / SW Ariquemes, Fzda / Rancho Grande, 11-XI- / 1994, C.W.O'Brien / blacklight trap”.

Differential diagnosis. Extremely similar to Sacosternum cruciphallus , S. emissarium and S. garciai by the combination of the absence of triangular areas at lateral margins of metaventrite, very narrow preepisternal plate of mesothorax, pronotum with fine microsculpture and with two very distinct sublateral longitudinal impressions. Males may be distinguished from S. garciai by posteriorly reduced median carina of the metaventrite (complete in S. garciai ) and from all these species by the morphology of the apical portion of the median lobe which is rather weakly widened and lacks lateral sclerites. Females may be distinguished from S. emissarium by the posterior emargination of abdominal ventrite 5 (absent in S. emissarium ); females of S. garciai and S. cruciphallus cannot be distinguished.

Description. Body widest ca at midlength, weakly convex in lateral view. Body length 1.6–1.8 mm (holotype: 1.7 mm), body width 0.9–1.2 mm (holotype: 1.1 mm); TL/TW ratio = 1.65.

Coloration. Dorsal side reddish brown, frons and lateral margins of pronotum brown; ventral side reddish brown; coxae, femora and tibiae reddish brown, palpi, antennae and tarsi yellowish.

Head. Clypeus with dense punctation consisting of moderately large rasp-like punctures, each puncture bearing fine decumbent seta; interstices with fine microsculpture; anterior margin of clypeus slightly convex. Interocular area with median triangular area defined by shallow depressions. Frons with moderately dense punctation consisting of moderately large rasp-like punctures, punctures of same shape on mesal and lateral portion; interstices with fine mesh-like microsculpture. Eyes large, separated by 1.6× of width of one eye. A tuft of yellowish erect setae anteriorly of each eye absent. Mentum 1.5× wider than long, anterior margin slightly emarginate; anteromedian part slightly impressed, bearing sparse punctation consisting of large nearly circular punctures; interstices with fine mesh-like microsculpture. Maxillary palpomeres 2 and 4 ca. twice as long as palpomere 3. Scapus slightly longer than antennomeres 2–6 combined.

Prothorax. Pronotum continuously arcuate on posterior margin; shallowly sulcate; bearing two weak but distinct longitudinal impressions sublaterally. Pronotum forming continuous curve with elytra in lateral view; posterolateral corners rounded, lateral margin weakly sinuate, with narrow marginal rim. Pronotal punctation dense, slightly denser than that on frons, consisting of rather large deeply impressed rasp-like punctures; interstices with microsculpture. Transverse row of punctures on posterior margin of pronotum absent. Median carina of prosternum narrow; projecting slightly anteriad mesally, straight in lateral view. Median portion of prosternum 1.5× wider than long; additional lateral expansions of the prosternal shield not developed; postero-mesal projection with shallow notch. Lateral margin of antennal grooves subangulate.

Mesothorax. Scutellar shield lacking punctures, interstices with fine mesh-like microsculpture. Elytral series 1–5 and 7 arising basally, series 6 and 8 arising subbasally; series 9 not joining series 8 anteriorly, nearly reaching elytral base. Serial punctures small; transverse, sparsely arranged, slightly larger than interval punctures. Lateral serial punctures connected to each other by a fine and sharp longitudinal furrow. Elytral intervals moderately convex at suture, becoming slightly more convex laterad and posteriad; series weakly impressed mesally and laterally. Interval punctation consisting of small, transversely scar-like punctures arranged in series at least on some intervals. Epipleura ca. as wide as pseudepipleura. Preepisternal plate very narrow, suboval, or nearly linear, 3.3× longer than wide; median part bearing densely arranged large setiferous punctures; plate narrowly attached to metaventrite; posterior part of preepisternal elevation slightly overlapping anterior margin of metaventrite.

Metathorax. Metaventrite ca. as long as preepisternal elevation of mesothorax, median portion markedly differing from lateral portion in punctation and microsculpture; punctation of median portion moderately dense, consisting of rather large nearly circular setiferous punctures; interstices without microsculpture, shiny. Lateral portions of anterolateral ridges arcuately bent posteriad, concave sublaterally. Length of median carina of metaventrite ridge sexually dimorphic, reaching anterior third of metaventrite length in male and posterior margin of metaventrite in female. Anterior margin of metaventrite indistinctly crenulate. Lateral portions of femoral lines not developed, the lateral triangular area on metaventrite absent. Anepisternum 8.4× longer than wide.

Legs. Protibiae not emarginate on outer margin apically.

Abdomen. Abdominal ventrite 1 not crenulate anteriorly. Ventrites 2–4 with additional ridges, ventrite 5 flat; posterior margin of ventrites 1–4 finely denticulate; abdominal ventrite 5 emarginate medially in females.

Male genitalia. Aedeagus 0.67 mm long. Parameres 1.4× longer than phallobase, gradually narrowing from base to apex. Phallobase wide, 0.9× longer than wide. Median lobe nearly parallel-sided in basal 0.7, slightly widened in apical 0.3; pair of lateral subapical sclerites absent; apical sclerite wide. Gonopore present, situated subapically. Median portion of sternite 9 shallowly circular.

Variation. Uniform in most external characters examined. The only observed variability concerns the preepisternal plate of mesothorax which is partly reduced posteriorly in two specimens examined (the plate therefore appears shorter and widely separated from the anterior margin of the metaventrite).

Etymology. Derived from aura (Lat., glow) and blepsis (Greek; seeing, sight), i.e. seeing the glow, referring to the fact that all specimens were attracted at black light. Standing as a noun in apposition.

Biology. Unknown. All species were collected at light.

Distribution. Known only from the type locality.