Sacosternum garciai, 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 : 16-19

Sacosternum garciai sp. n.

(Figs. 3–4, 17–18, 36–37, 38–39, 46)

Type locality. Panama, Chiriquí Province, Boquete [coordinates ca. 8°46'N 82°26'W, altitude ca. 1100m].

Type material. Holotype: male ( UCDC): “Boquete PAN / Chirique Prov. / III 19 1977 / Henk Wolda”. Paratypes (12 spec.): PANAMA: 1 female ( CNC): same data as the holotype; 1 male ( NMPC): same label data with date “ VIII 12 1977 ”; 2 females ( CNC): same label data with date “ X 17 1977 ”; 1 female ( NMPC): same label data with date “ X 18 1977 ”; 1 spec. ( CNC): same label data with date “ IX 11 1977 ”; 1 female ( CNC): same label data with date “ VI 26 1977 ”; 1 male ( CMN): “ PANAMA: Chiriqui Prov. / 27.7 km W Volcan / Hartmann’s Finca / 08°45'N, 82°48'W / 1450m, 14–17 VI 1995 / J. Ashe & R. Brooks#231 / ex: flight intercept trap”. COSTA RICA: 1 male ( KSEM): “ COSTA RICA: Limon / Reventazon, Hamburg / Farm XI:10:1927 / leg. F. Nevermann // Field Mus. Nat. Hist. / 1966 / A. Beirig Colln. / Acc. Z-13812 // at light”; 1 female ( FMNH): same label data with date “XI:10:27”; 1 female ( FMNH): same label data with date “V:27:1935”. VENEZUELA: 1 male ( MALUZ): “ Venezuela Zulia / Dtto Maracaibo / San Jose de los / Altos 35 Km. N / O. de Laberinto / 1400m 18/ 19-VIII-1990 // Colector: / J. Camacho”.

Differential diagnosis. Extremely similar to Sacosternum auribleps , S. cruciphallus and S. emissarium by the combination of the absence of triangular areas at the lateral sides of metaventrite, very narrow preepisternal plate of mesothorax, pronotum with fine microsculpture and at least two very distinct sublateral longitudinal impressions. Males may be distinguished from these species by median carina of metaventrite reaching posterior margin of metaventrite (at least slightly reduced posteriorly in the remaining species) and rather narrow aedeagus and only moderately widened apical portion of the median lobe, bearing wide but rather small lateral sclerites. Females may be distinguished from S. emissarium by the posterior emargination of abdominal ventrite 5 (absent in S. emissarium ).

Description. Body widest ca at midlength, weakly convex in lateral view. Body length 1.4–1.9 mm (holotype: 1.7 mm), body width 0.9–1.1 mm (holotype: 1.1 mm); TL/TW ratio = 1.6.

Coloration. Dorsal side dark reddish brown, frons slightly darker; ventral side dark reddish brown; coxae, femora, tibiae and antennal clubs reddish brown, mouthparts, antennomeres 1–6 and tarsi yellowish.

FIGURES 15–22. Aedeagophores. 15–16: S. epulum ; 17–18: S. garciai ; 19–20: S. inconnivum ; 21–22: S. megalopus . 15, 17, 19, 21: whole aedeagus, dorsal view; 16, 18, 20, 22: detail of the apical portion of the median lobe.

Head. Clypeus with moderately dense punctation consisting of moderately large semicircular rasp-like to scar-like punctures, each puncture bearing fine decumbent seta; interstices with fine microsculpture; anterior margin of clypeus slightly convex. Interocular area with triangular area defined by shallow depressions. Frons with moderately dense punctation consisting of moderately large semicircular scar-like punctures; interstices with fine mesh-like microsculpture. Eyes large, separated by 2.2× 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 sparse punctation consisting of large, nearly circular punctures; interstices with fine mesh-like microsculpture. Maxillary palpomeres 2 and 4 ca. 1.5× as long as palpemere 3. Scapus slightly longer than antennomeres 2–6 combined.

Prothorax. Pronotum forming continuous curve with elytra in lateral view, continuously arcuate on posterior margin; 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 dense, slightly denser than that on frons, punctation consisting of small, semicircular rasp-like punctures; interstices with 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 1.2× wider than long; additional lateral expansions of prosternal shield absent; posteromesal projection with shallow notch. Lateral margin of antennal grooves rounded.

Mesothorax. Scutellar shield bearing few minute punctures, interstices with fine mesh-like microsculpture. Elytral series 1–5 and 7 arising basally, series 6 and 8 arising subbasally; series 9 joining series 8 anteriorly, slightly abbreviated anteriorly, arising in basal 0.1 of elytral length. Serial punctures small, transverse, sparsely arranged, slightly larger than interval punctures. 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 arranged to series at least on some intervals, consisting of minute transversely scar-like punctures. Epipleura ca. as wide as pseudepipleura. Preepisternal plate very narrow, 4.0× longer than wide, suboval, median part flat, bearing densely arranged small setiferous punctures; plate narrowly 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 rather sparsely arranged small setiferous punctures; interstices without microsculpture, shiny. Anterolateral ridge bending arcuately 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 line absent, triangular area at lateral sides of metaventrite absent. Anepisternum 10.0× longer than wide.

Legs. Protibiae not emarginate on outer margin apically.

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 weakly emarginate medially in females.

Male genitalia. Aedeagus 0.67 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 0.6, moderately widening in apical 0.4. A pair of lateral subapical sclerites present; apical sclerite wide; lateral sclerites wide, each with small lateral tooth in almost perpendicular position to apical sclerite. Gonopore present, situated subapically. Median portion of sternite 9 shallowly circular.

Variation. A rather wide variation in the shape of the lateral sclerites of the median lobe was observed among the examined specimens, which seems to be at least partly caused by the different direction and “folding” of these sclerites in different aedeagophores examined. As the specimens examined agree in all remaining characters including of the entirely developed median carina of the metaventrite in males (which is unique for this species within the “ S. cruciphallus complex”), we consider these variation as intraspecific.

Etymology. The species is dedicated to Mauricio García (MALUZ), a specialist on Neotropical Hydrophilidae and primary collaborator of the project on Aquatic Insects of Venezuela.

Biology. Unknown. Some of the specimens examined were collected at light or in flight intercept traps.

Distribution. Known from Costa Rica (Limon Province), Panama (Chiriquí Province) and western Venezuela (Zulia State). Probably rather widely distributed in southern Central America and north-western South America.