Sacosternum inconnivum, 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 : 19-24

Sacosternum inconnivum sp. n.

(Figs. 19–20, 47, 55)

Type locality. Panama, Canal Zone, Barro Colorado Island [coordinates ca. 9°09'N 79°50'W, altitude ca. 0–70 m a.s.l.].

Type material. Holotype: male ( KSEM): “ PANAMA: Panama / Barro Colorado Isd. / 09°11'N, 79°51'W / 6 Aug. 1994, D. Banks / ex: flight intercept trap”. Paratypes (4 spec.): PANAMA: 1 female ( KSEM): “ PANAMA: Colon / Parque Nac. Soberania / Pipeline Rd. Km 6.1 / 09°07'N 79°45'W, 40m / 7–21 June 1995 / J. Ashe, R. Brooks #265 / ex: flight intercept trap”; male ( UCDC): “Barro Colorado I / CZ Panama VIII / 25 ,27 1986 / Henk Wolda // TRAP / 2B”. COSTA RICA: 1 male ( NMPC): “ COSTA RICA: Heredia Province / 16km SSE La Virgen, 1070m / 10°16'N 84°05'W / 10–21.iv.2001; 11/TN/19/029 / INBio-OET- ALAS transect”; 1 male ( INBio): “Rancho Quemado, 200m / Peninsula de Osa, Prov. / Puntarenas, Costa Rica / Oct 1992, F. Quesada / L-S 292500, 511000”.

Differential diagnosis. Easily distinguishable from all known Sacosternum species except S. delta by the shape of the anterolateral ridge on the metaventrite which is convex and subangulate sublaterally. For differential characters from S. delta , see this species or the respective couplets in the key.

FIGURES 27–37. 27, 30: S. cruciphallus ; 28, 32: S. megalopus ; 29: S. delta ; 31: Sacosternum sp. A; 33–34: S. auribleps (33: male; 34: female); 35: Sacosternum sp., female belonging to the “ cruciphallus complex”, Mexico, Veracruz, Canyon SW Rio Metlac; 36–37: S. garciai . 27: head, dorsal view; 28: head, frontal view; 29–30: pronotum; 31–33: abdomen, ventral view; 34–35: abdominal ventrites 4–5; 36: malesternite 9; 37: male sternite 8.

FIGURES 38–49. 38–39, 46: S. garciai ; 40, 45, 49: Sacosternum sp. B; 41, 43: S. auribleps ; 42, 48: S. lebbinorum ; 44: S. delta ; 47: S. inconnivum . 38: head, ventral view; 39: prosternum, ventral view; 40–42: mentum; 43–45: prosternal shield and procoxae; 46–49: preepisternal elevation of mesothorax.

Description. Body widest ca at midlength, weakly convex in lateral view. Body length 1.7–2.0 mm (holotype: 2.0 mm), body width 1.1–1.2 mm (holotype: 1.2 mm); TL/TW ratio = 1.6.

Coloration. Dorsal side reddish brown; ventral side reddish brown; legs, mouthparts and antennae yellowish.

Head. Clypeus with moderately dense punctation consisting of moderately large nearly circular punctures, each puncture bearing fine decumbent seta; interstices without microsculpture; anterior margin of clypeus slightly concave. Interocular area with triangular area defined by shallow depressions. Frons with dense punctation consisting of moderately large circular punctures; interstices without microsculpture. Eyes large, separated by 2.4× of width of one eye. A tuft of yellowish erect setae anteriorly of each eye absent. Mentum 2.0× wider than long, anterior margin slightly emarginate, anteromedian part slightly impressed; surface with moderately dense punctation consisting of moderately large circular punctures; interstices without distinct microsculpture. Maxillary palpomeres 2 and 4 ca. 1.5× as long as palpomere 3. Scapus shorter than antennomeres 2–6 combined.

Prothorax. Pronotum distinctly more convex than elytra in lateral view, weakly bisinuate on posterior margin; surface evenly convex, or shallowly sulcate, bearing indistinct longitudinal impression posteriorly on each side. Posterolateral corners forming obtuse angle; lateral margin angulate, with narrow marginal rim. Pronotal punctation dense, as dense as on frons, consisting of rather small rounded punctures; interstices without microsculpture. Transverse row of punctures on posterior margin of pronotum absent. Median carina of prosternum narrow; projecting anteriad mesally, with anterior portion extending into small tooth in lateral view. Median portion of prosternum 1.9× wider than long; additional lateral extensions of prosternal shield developed; postero-mesal projection with shallow notch. Lateral margin of antennal grooves subangulate.

Mesothorax. Scutellar shield bearing few minute circular punctures, interstices without microsculpture. Elytral series 1–5 arising basally, series 6–8 arising subbasally; series 9 not joining series 8 anteriorly, abbreviated anteriorly, arising in basal 0.15 of elytral length. Serial punctures moderately large, rounded, sparsely arranged, much larger than interval punctures. Serial punctures connected to each other by a fine and sharp longitudinal furrow. Elytral intervals weakly convex at suture, becoming slightly more convex laterad and posteriad; series deeply impressed mesally and laterally. Interval punctation arranged in series at least on some intervals, consisting of small, scar-like punctures. Epipleura ca. as wide as pseudepipleura. Preepisternal plate narrow, 1.8× longer than wide, arrow-head shaped, with median longitudinal carina, bearing rather dense and coarse setiferous punctation; elevation widely attached to metaventrite, posterior part slightly overlapping anterior margin of metaventrite.

Metathorax. Metaventrite ca. as long as preepisternal elevation of mesothorax; its median portion markedly differing from lateral portion in punctation and microsculpture. Punctation of median portion of metaventrite consisting of densely arranged small circular setiferous punctures; interstices without microsculpture, shiny. Anterolateral ridge arcuately bending posteriad towards lateral margin of metaventrite, subangulate sublaterally. Length of median ridge of metaventrite sexually dimorphic, reaching posterior fifth in male and posterior margin of metaventrite in female. Anterior margin of metaventrite crenulate. Lateral portion of femoral line present between anterolateral ridge and lateral sides of metaventrite, delimiting a triangular area. Anepisternum 11.5× longer than wide.

Legs. Protibiae with shallow apical emargination on outer margin.

Abdomen. Ventrite 1 not crenulate anteriorly. Ventrites 2–4 with longitudinal ridges, ventrite 5 flat; posterior margin of ventrites 1–4 finely denticulate; abdominal ventrite 5 without emargination in both sexes.

Male genitalia. Aedeagus 0.85 mm long. Parameres as long as phallobase, narrow basally, continually narrowing apicad. Phallobase narrow, 1.5× longer than wide. Median lobe narrow basally, slightly widening up to apical fourth, sclerotized median portion then triangularly narrowing apicad. A pair of lateral subapical sclerites present; apical sclerite narrow; lateral sclerites narrow but not extremely long, forming a sharp angle to apical sclerite. Gonopore indistinct. Median portion of sternite 9 shallowly circular.

Variability. None observed.

Etymology. Derived from inconnivus (Lat., never closing the eyes), reflecting the large eyes of this species typical for the genus Sacosternum . Adjective.

Biology. Unknown. Some specimens examined were collected at flight intercept trap.

Distribution. Known from Costa Rica (provinces of Heredia and Puntarenas) and Panama (Canal Zone).