Baconia atricolor, Caterino, Michael S. & Tishechkin, Alexey K., 2013

Caterino, Michael S. & Tishechkin, Alexey K., 2013, A systematic revision of Baconia Lewis (Coleoptera, Histeridae, Exosternini), ZooKeys 343, pp. 1-297 : 270-272

Baconia atricolor sp. n. Figs 84 C–D 86Map 23

Type locality.

COSTA RICA: Guanacaste: Sta. Rosa National Park [10.3°N, 85.62°W].

Type material.

Holotype male: "Est. Sta. Rosa, 300m, P.N. Sta. Rosa, Guanacaste Costa Rica, 13 a 28 jun 1992, III curso Parataxon. L-N 313000, 359800" / "INBIO CRI000492752 (INBIO). Paratypes (2): COSTA RICA:1: Guanacaste: P. N. Guanacaste, Los Almendros, 1-22.vii.1992, E. Lopez (INBI); 1: x.1983, D. Janzen & W. Hallwachs (INBI).

Other material.

BRAZIL: 1: Mato Grosso:Mpio. Cuiaba, Fazenda Mutuca, 15.3145°S, 55.9703°W, 6.iii.2009, FIT, J. Rocha (CEMT), 1: 6.xii.2008, FIT, F. Gava & J. Rocha (FMNH).

Diagnostic description.

Length: 1.7-2.0mm, width: 1.2-1.8mm; body broadly ovoid, strongly depressed, glabrous; rufopiceous throughout; frons weakly elevated over antennal bases, depressed in middle, ground punctation of frontal disk very fine, inconspicuous, with few irregularly scattered coarse punctures on epistoma, middle of frons and near vertex, frontal stria present along inner margin of eye and across front but narrowly interrupted over antennae, and more broadly interrupted at middle; supraorbital stria absent; epistoma broadly depressed, weakly emarginate apically; labrum about 3 ×wider than long, apical margin emarginate; antennal scape short, club rounded, expanded to apex; pronotal sides evenly arcuate to apex, marginal stria complete along lateral and anterior margins, weakly crenulate in front; lateral submarginal pronotal stria absent, pronotal disk not depressed in anterior corners, ground punctation of pronotal disk very fine, inconspicuous, sparsely interspersed with small secondary punctures in lateral thirds; elytra with two complete epipleural striae, outer subhumeral stria absent, inner subhumeral stria present in basal fifth, dorsal striae 1-2 complete, 3rd stria slightly abbreviated apically, sinuate in apical half, 4th stria present in basal third, weakly arched toward suture at base, 5th stria absent, sutural stria present in apical half, elytral disk with sparse punctures in apical third; prosternum moderately broad, weakly convex, keel shallowly emarginate at base, carinal striae subparallel, nearly complete, may be united along extreme basal margin; prosternal lobe slightly over one-half keel length, apical margin rather rounded, marginal stria obsolete at sides; mesoventrite weakly produced at middle, marginal stria complete, mesometaventral stria strongly arched forward, crenulate, detached at sides; lateral metaventral stria extending posterolaterad toward middle of metacoxa, outer lateral stria present along basal two-thirds of inner stria, metaventral disk impunctate at middle; abdominal ventrite 1 with inner lateral stria curved mediad, abbreviated apically, outer lateral stria present as short postcoxal fragment, middle portion of disk impunctate; protibia very weakly 4-dentate, outer margin serrulate; mesotibia with two marginal spines; outer metatibial margin smooth; propygidium without basal stria, discal punctures separated by about their diameters in basal half, smaller and sparser apically; propygidial gland openings conspicuous, about one-third from basal and lateral margins; pygidium with ground punctation fine, uniformly interspersed with small, sparse secondary punctures. Male genitalia (Fig. 86): T8 slightly longer than wide, sides subparallel in basal two-thirds, narrowing to apex, basal emargination rather deeply arcuate, apical emargination narrow, ventrolateral apodemes extending to about midpoint beneath, separated by two-thirds T8 width; S8 halves approximate along most of midline, base rounded, sides subparallel, apical guides narrow, widened slightly toward apex, connected by fine dorsal membraneous velum; T9 with proximal apodemes thin, almost one-half total length, apices of dorsal lobes convergent, acute, ventrolateral apodemes strongly dentate, meeting at midline beneath; S9 desclerotized along midline, stem moderately broad, widening slightly toward base, apical arms slightly divergent, curved, apices acute; tegmen with sides subparallel in basal half, widened slightly near apex, rather thick, very weakly curved in lateral aspect; median lobe one-half tegmen length; basal piece one-third tegmen length.

Remarks.

This species is among the few strongly flattened, piceous species. Its pattern of elytral striation is also unique, with the 4th stria represented by a basal arch, the 3rd stria abbreviated and sinuate apically, and the sutural stria very short and apical (Fig. 84C). Preliminary phylogenetic analyses place this species among those of the Baconia salobrus group, and given its coloration this is conceivable. However, the body form is very different, being strongly flattened in Baconia atricolor as opposed to the strongly convex body form of all salobrus group species, and we prefer not to include it at this point. Male genitalia are similar, but without exhibiting any outstanding synapomorphies.

This species is known from a couple of broadly disjunct areas. The Brazilian specimens, from Mato Grosso, are in nearly all respects very similar to those from Costa Rica, but they have slightly denser lateral pronotal punctation, and have the S8 of the male genitalia more broadly expanded apically. Given the limited material available, we prefer to consider these unusual representatives of the same species, but we exclude them as types.

Etymology.

This species is named in reference to its black coloration, unusual among flattened Baconia spp.