Baconia riouka (Marseul, 1861)

Caterino, Michael S. & Tishechkin, Alexey K., 2013, A systematic revision of Baconia Lewis (Coleoptera, Histeridae, Exosternini), ZooKeys 343, pp. 1-297 : 216-218

Baconia riouka (Marseul, 1861) Figs 62 A–D63A–C, G, I–JMap 19

Phelister riouka Marseul, 1861: 158; Pseudister riouka : Bickhardt 1917: 165; Baconia riouka : Mazur 1997: 25.

Type locality.

BRAZIL: Rio de Janeiro [22.9°S, 43.2°W].

Type material.

Lectotype, sex undetermined, here designated (NHRS): "Rio. Jan" / "F. Sahlb." / “Typus” / “Type” / "6910 E91 +" / "LECTOTYPE Phelister riouka Marseul M.S.Caterino & A.K.Tishechkin des. 2010". This species was described from an unspecified number of specimens, and the lectotype designation fixes primary type status on the only known original specimen.

Other material.

PARAGUAY: 1: Itapua, 17 km W Karonay, San Rafael Reserve, 26°45'53"S, 55°50'37"W, 90-110m, 18-21.xi.2000, FIT, Z.H.Falin (SEMC); 1: Cazaapa, Hermosta, prop. Sosa family, San Rafael Reserve, 26°19'15"S, 55°44'55"W, 90m, 3-6.xii.2000, FIT, Z.H.Falin (SEMC). 2: BRAZIL: Santa Catarina, Nova Teutonia, i.1973, F. Plaumann (FMNH).

Diagnostic description.

Length: 2.4-2.5mm, width: 2.2-2.3mm; body broadly oval, moderately depressed, glabrous; color piceous, shining; frons broad, interocular margins convergent dorsad, frontal disk transversely, arcuately elevated above and between antennal bases, frontal stria absent along margin of eyes but complete across front, finely carinate, frontal disk broadly depressed behind, ground punctation conspicuous, rather dense; supraorbital stria absent; antennal scape short, thick, club slightly asymmetrically oblong; epistoma more or less convex, straight across apex; labrum about 2 ×wider than long, apical margin outwardly arcuate; mandibles narrow, convex, left mandible with small basal tooth, right mandible edentate; pronotum wide, sides evenly arcuate from base to apices, lateral marginal and submarginal striae close, parallel, separate to anterior corner, marginal stria usually rounding corner, ending free, submarginal stria joining or detached from anterior marginal stria, pronotal disk narrowly depressed along submarginal stria, largely impunctate at middle, with very small, sparse punctures becoming evident in lateral thirds; elytra with three epipleural striae, outer subhumeral stria present in basal half, weak, inner subhumeral stria complete, dorsal striae 1-3 complete, 4th stria complete or interrupted medially, 5th stria absent, sutural stria present in apical half to two-thirds, elytral disk punctate along apical margin; prosternal keel moderately broad, weakly convex, truncate or very shallowly emarginate at base, with more or less complete, subparallel carinal striae, separate throughout; prosternal lobe about one-half keel length, apical margin rounded, marginal stria present only at middle; mesoventrite broadly, shallowly emarginate, may be very weakly produced at middle, marginal stria interrupted for nearly width of prosternal keel; mesometaventral stria broadly arched forward, detached laterally from inner lateral metaventral stria, which curves obliquely posterad toward outer third of metacoxa, outer lateral metaventral stria very short; metaventral and abdominal disks impunctate at middle; abdominal ventrite 1 with single complete lateral stria; protibia tridentate, with median marginal denticle rather weak, margin serrulate; mesotibia with two small marginal spines; outer metatibial margin with fine subbasal denticle; propygidium short, wide, lacking basal stria, male propygidium biimpressed, each side with small area of dense ground punctation, devoid of secondary punctures, female propygidium only very weakly depressed, with secondary punctures more uniformly scattered; pygidium with fine ground punctation interspersed with small secondary punctures, separated by 2-3 × their diameters. Male genitalia (Figs 63 A–C, G, I–J): T8 slightly longer than wide, basal emargination moderately deep and narrow, sides subparallel, apical emargination subacute, ventrolateral apodemes well sclerotized, separated by half T8 width, projecting distad to about midpoint; S8 longer than broad, halves approximate at inner bases only, narrowing apically, apical guides weakly developed at sides, apices narrowly rounded, moderately well-sclerotized; T9 with proximal apodemes narrow, about one-third total length, apices weakly divergent, bearing a few fine setae, ventrolateral apodemes bluntly rounded beneath; T10 cordate, with distinct desclerotization along middle part of anteroposterior midline; S9 short, broadly subtruncate at base, narrowed to near apex, apical arms thin, divergent, apical emargination broadly arcuate; tegmen nearly parallel-sided throughout, subangulately narrowed to apex, in lateral view showing a pronounced dorsal hump near midpoint, becoming thinner apically, and with a distinct ventral longitudinal keel; median lobe about one-half tegmen length; basal piece short, about one-fifth tegmen length.

Remarks.

This species is highly distinctive, given the characters of the group, in addition to its black, non-metallic coloration of the elytra (Fig. 62A), and its male’s relatively simple propygidium with only shallow micropunctate depressions on each side (Fig. 62D). Apparently the shallow depressions of the male are associated with a median displacement of the propygidial glands, which are, in the female, clearly visible rather close to the sides, but not obviously visible in males.