Baconia isthmia, 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 : 59-61

Baconia isthmia sp. n. Figs 15 A–C, G, I–JMap 3

Type locality.

MEXICO: San Luis Potosí: El Salto Falls [22.58°N, 99.37°W].

Type material.

Holotype male: "MEXICO: San Luis Potosí: El Salto Falls, 12 km NW El Naranjo, 26 July 1990, 400 m, J.S.Ashe, K.-J.Ahn, R.Leschen #246 ex.fungusy log" / “SEMC0903644” (SEMC). Paratypes (3): 1: BELIZE: Cayo: Las Cuevas, 8.v.1994 (BMNH). 2: MEXICO: Puebla: 4.7 mi. SW La Cumbre, 5200 ft., 23.vii.1987, Kovarik & Schaffner (CHPWK).

Diagnostic description.

Length: 2.1-2.2mm, width: 1.8-1.9mm; body broadly elongate oval, depressed, glabrous; color metallic blue to greenish-blue over most of dorsum, pronotum may be more distinctly greenish (not in type), venter rufobrunneus; frons elevated over antennal bases, depressed at middle, ground punctation fine, with few coarse punctures at middle and near vertex, frontal stria present along inner margin of eye, curving inward at front, interrupted over antennal bases and at middle; antennal scape short, club nearly circular; epistoma truncate apically; labrum about 4 ×wider than long, weakly bisinuate apically; both mandibles with acute basal tooth; pronotum with sides increasingly arcuate to apex, marginal stria complete along lateral and anterior margins, lateral submarginal stria absent, disk depressed along anterior fifth of lateral margin, ground punctation of pronotal disk very fine, coarser secondary punctures limited to narrow lateral region; elytra with two complete epipleural striae, outer subhumeral stria absent, inner subhumeral stria present as basal and median fragments, dorsal striae 1-3 complete, 4th stria complete or interrupted in basal half, 5th stria weakly impressed in apical half to two-thirds, abbreviated from apex, sutural stria shorter than 5th anteriorly, but extending further to apex, elytral disk with few coarse punctures in apical sixth; prosternum moderately broad, weakly convex, keel subacutely emarginate at base, carinal striae complete, depressed at bases, slightly sinuate, weakly divergent anterad; prosternal lobe about two-thirds keel length, apical margin rounded, marginal stria obsolete at sides; mesoventrite subacutely produced at middle, marginal stria interrupted for width of prosternal keel; mesometaventral stria strongly arched forward, weakly crenulate, detached from lateral metaventral stria, which extends from inner corner of mesocoxa posterolaterad toward outer corner of metacoxa, abbreviated apically, outer lateral metaventral stria absent, metaventral disk impunctate at middle; abdominal ventrite 1 with single, complete lateral stria, middle portion of disk lacking coarse punctures; protibia 4-5 dentate, the basal denticles weak, outer margin serrulate between teeth; mesotibia with two weak marginal spines; outer metatibial margin smooth; transverse basal propygidial stria varied, complete or represented only by subserially arranged punctures, punctures otherwise rather small and sparse, separated by 1 –2× their diameters; propygidial gland openings evident about one-third behind anterior margin, about one-fourth width from each lateral margin; pygidium with ground punctation rather dense in apical half, secondary punctation evident only along basal margin. Male genitalia (Figs 15 A–C, G, I–J): T8 slightly shorter than broad, sides weakly widened in basal one-third, convergent to apex, basal emargination broad, deep, weakly acute at middle, basal rim slightly explanate, apical emargination narrow, shallow, with ventrolateral apodemes separated by about one-half maximum T8 width, extending about one-half distad beneath, obsolete in apical half; S8 divided, inner margins approximate at base, weakly divergent in basal half, strongly divergent to apex, bearing conspicuous fringe of setae in apical one-third, outer margins subparallel, apical guides well developed in apical half, narrowly lobate apically; T9 with basal apodemes thin, about two-thirds total length, T9 apices narrow, bluntly subacute, weakly opposed, glabrous, ventrolateral apodemes weakly projecting beneath; S9 weakly widened at base, head broad, with apicolateral points curved, horn-like, desclerotized along midline, with narrow apicomedial division; tegmen with sides subparallel to near apex, apical one-fourth weakly bulbous, broadly rounded at apex, dorsobasal edge projecting, tegmen more or less straight in lateral aspect; median lobe about one-half tegmen length; basal piece about one-fourth tegmen length.

Remarks.

Baconia isthmia is very closely related to Baconia scintillans , above, both lacking a submarginal lateral pronotal stria, and exhibiting an isolated median fragment of the mesometaventral stria. Baconia isthmia is slightly smaller, a little more distinctly flattened, has a distinct transverse propygidial stria, has the 4th elytral stria reaching the base (may be interrupted), and lacks a median fragment of the inner subhumeral stria. There are slight genitalic differences as well, with the tegmen of Baconia isthmia slightly shorter and more spatulate apically, and the 8th sternite of the male less elongate, than those of Baconia scintillans or Baconia godmani .

Etymology.

This species is named for Isthmian region (de Tehuantepec) that spans the region inhabited by this species.