Sacosternum epulum, 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 : 15-16

Sacosternum epulum sp. n.

(Figs. 15–16)

Type locality. Brazil, Santa Catharina State, Nova Teutonia, 300–500 m a.s.l. [coordinates ca. 27° 03'S 52°24'W].

Type material. Holotype: male ( FMNH): “ BRASIL: Sta. Catharina / Nova Teutonia / X:1972, 300– 500m / leg. F. Plaumann”. Paratypes (9 spec.): BRAZIL: 1 male ( FMNH): same data as the holotype; 1 male, 4 spec. ( FMNH, NMPC): “Nova Teutonia, Sta. / Catharina, BRAZ. / III:15:1952 / Fritz Plaumann leg. // bei Eciton / praedator ”; 2 spec. ( FMNH, NMPC): same label data with date “III:22:52”; 1 spec. ( FMNH): same label data with date “III:19:1952”; 1 female ( FMNH): same label data with date “IV:7:1953”.

Differential diagnosis. The species can be easily recognized from all other Sacosternum species by the combination of absence of the triangular area at lateral sides of the metaventrite, pronotal interstices without microsculpture (in contrast to species of “ S. cruciphallus complex”), head without tufts of erect hairs (“horns”) anteriorly of each eye and abdominal ventrite 5 without longitudinal ridges (both latter characters distinguish it from S. megalopus ). In all these characters S. epulum agrees with S. sp. B, but it may be easily recognized from this species by narrowly suboval preepisternal elevation and abdominal ventrites 2–4 with longitudinal ridges.

Description. Body widest ca at midlength, weakly convex in lateral view. Body length 1.9–2.1 mm (holotype: 2.0 mm), body width 1.2–1.3 mm (holotype: 1.3 mm); TL/TW ratio = 1.6.

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

Head. Clypeus with dense punctation consisting of rather small, slightly rasp-like punctures, each puncture bearing fine decumbent seta; interstices without microsculpture; anterior margin of clypeus truncate. Interocular area with median triangular area defined by shallow depressions. Frons with dense punctation consisting of moderately large semicircular rasp-like punctures, interstices without microsculpture. Eyes large, separated by 2.9× 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 in contrast to lateral portions; surface with dense punctation consisting of rather large, rounded punctures; interstices with fine mesh-like microsculpture. Maxillary palpomeres 2 and 4 ca. 1.5× as long as palpomere 3. Scapus slightly longer than antennomeres 2–6 combined.

Prothorax. Pronotum forming continuous curve with elytra in lateral view, continuously arcuate on posterior margin; surface shallowly sulcate, bearing two weak but distinct longitudinal impressions on each side. Posterolateral corners rounded, lateral margin weakly sinuate, with narrow marginal rim. Pronotal punctation moderately dense, as dense as on frons, punctures moderately large, rounded; interstices without microsculpture. Transverse row of punctures on posterior margin of pronotum absent. Median carina of prosternum narrow, projecting anteriad mesally, straight in lateral view. Median portion of prosternum 1.45× wider than long; additional lateral expansions of the prosternal shield not developed; postero-mesal projection with shallow notch. Lateral margin of antennal grooves rounded.

Mesothorax. Scutellar shield bearing a few minute punctures, interstices with fine mesh-like microsculpture. Elytral series 1–7 arising basally, series 8 arising subbasally; series 9 joining series 8 anteriorly, nearly reaching elytral base. Serial punctures moderately large, transverse, sparsely arranged, slightly larger than interval punctures. Serial punctures not connected to each other with a fine and sharp longitudinal furrow. Elytral intervals weakly convex at suture, becoming slightly more convex laterad and posteriad; series weakly impressed mesally and laterally. Interval punctation arranged in series at least on some intervals, consisting of small transverse, scar-like punctures. Epipleura slightly wider than pseudepipleura. Preepisternal plate very narrow; 4.8× longer than wide, suboval; median part flat, bearing densely arranged moderately large setiferous punctures; plate narrowly attached to metaventrite, its posterior part slightly overlapping over 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 of metaventrite consisting of densely arranged, moderately large punctures each bearing long pale seta; interstices without microsculpture, shiny. Anterolateral ridge arcuately bending posteriad towards lateral margin of metaventrite, concave sublaterally. Length of median ridge of metaventrite similar in both sexes, reaching posterior margin of metaventrite. Anterior margin of metaventrite indistinctly crenulate. Lateral portion of femoral lines absent, triangular area at sides of metaventrite missing. Anepisternum 10.0× 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 entire in both sexes.

Male genitalia. Aedeagus 0.70 mm long. Parameres 1.3× longer than phallobase, rather narrow basally, continually narrowing apicad. Phallobase narrow, 1.2× longer than wide. Median lobe narrow in basal 0.7, slightly widened in apical 0.3. A pair of lateral subapical sclerites present; apical sclerite wide, lateral sclerites narrow but not extremely long, forming a sharp angle to apical sclerite. Gonopore present, situated subapically. Median portion of sternite 9 shallowly circular.

Variation. Not observed.

Etymology. Epulum (Lat., feast, banquet), reflecting one of the paratypes collected as a “guest on a banquet” of the army ants of the genus Labidius. Standing as a noun in apposition.

Biology. One of the paratypes was collected in association with the army ant Labidius praedator (F. Smith, 1858) ( Formicidae , Ecitoninae ).

Distribution. Known only from the type locality.