Operclipygus pygidialis (Lewis, 1908)

Caterino, Michael S. & Tishechkin, Alexey K., 2013, A systematic revision of Operclipygus Marseul (Coleoptera, Histeridae, Exosternini), ZooKeys 271, pp. 1-401 : 360-363

Operclipygus pygidialis (Lewis, 1908) Figs 101 A–B102A–C, HMap 34

Phelister pygidialis Lewis, 1908: 157; Pseudister pygidialis : Hinton (1935c: 14); Phelisteroides pygidialis : Wenzel and Dybas (1941: 454); Operclipygus pygidialis : Wenzel (1976: 259).

Type locality.

Not specified beyondParaguay.

Type material.

Lectotype, here designated, probably male: "Paraguay, Dr. Bohls" / "LECTOTYPE Phelister pygidialis Lewis M.S.Caterino & A.K.Tishechkin des. 2010" (BMNH). 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.

ECUADOR: Napo: 1: 20 km S. Tena, 600m, S. Peck, 11.vii. 1976, Berlese forest litter (FMNH). PERU: Junín: 1: ~16km NW Satipo, Rio Venado, 11°11.677'S, 74°46.137'W, 1150m, 3-8.iii.2010, A.V. Petrov (AKTC).

Diagnostic description.

Length: 1.62-2.06 mm, width: 1.31-1.72 mm; body rufescent, elongate oval, widest behind elytral humeri; frons more or less flat, frontal stria with sides divergent between eyes, weakly sinuate over antennal bases, complete, arcuate anteriorly; epistoma flat at base, weakly convex anteriorly; labrum short, about one-third as long as wide, apex straight; left mandible untoothed, right with acute basal tooth; pronotal disk weakly flattened at base, with small, indistinct prescutellar impression; ground punctation of pronotal disk fine and sparse, but conspicuous, without coarser punctures at sides; marginal pronotal stria complete at side, ending just mesad anterior corner; lateral submarginal stria complete at side, extending forward to anterior margin, replacing marginal for a short distance, ending behind eye; anterior submarginal stria present, briefly recurved posterad at sides; median pronotal gland openings situated laterad ends of anterior submarginal stria; elytron with single complete, sinuate epipleural stria, marginal bead broad and smooth beneath; outer subhumeral stria fine, complete, inner subhumeral absent, striae 1-3 complete, 4th stria present in apical half, 5th stria present in apical third, connected to apex of 4th stria by apical arch, sutural stria present in apical two-thirds, markedly widened anterad; prosternal keel produced, arcuate at base, carinal striae complete, convergent from base to middle, diverging slightly anteriorly, connected by anterior arch; prosternal lobe narrow, long, with complete marginal stria; mesoventral margin shallowly emarginate, with complete, fine marginal stria; mesometaventral stria arched forward at middle, sinuate at side, lateral metaventral stria extending toward outer corner of metacoxa, abbreviated at apex; 1st abdominal ventrite with two complete lateral striae; ventrites 2-4 with single regular series of small punctures at sides, obsolete at middle; propygidium about two-thirds length of pygidium (which appears shorter than normal, rather than propygidium appearing longer than normal), with uniform medium punctures separated by about their diameters, with fine sparse ground punctation interspersed; pygidium with fine, dense ground punctation, with larger punctures sparse, more concentrated along basal margin and onto basomedial part of disk; marginal pygidial sulcus deep, strongly crenulate on inner and outer edges. Male genitalia (Figs 102 A–C, H): accessory sclerites absent; T8 with sides evenly convergent from near base to apex, basal emargination deep and broad, meeting basal membrane attachment line at middle, apices obliquely subtruncate, with narrow apical emargination, ventrolateral apodemes broadest near base, almost meeting at midline, narrowed apicad; S8 with sides parallel, apical guides approximately consistent in width from base to apex, ventral halves approximate in basal fourth, divergent to apex; T9 with sides evenly rounded, apices acute, not strongly convergent; halves of T10 approximate along midline; S9 with stem narrow, widened only slightly to narrowly rounded base, with very small apical emargination and separate apical flanges; tegmen widest just beyond midpoint, evenly narrowed to base and apex, apical half curving downward weakly, with medioventral process ‘U’ -shaped, projecting beneath near midpoint of tegmen; basal piece about one-third tegmen length; median lobe about one-fourth tegmen length, broad portion of proximal apodemes short, separate.

Remarks.

Operclipygus pygidialis has some superficial similarity with members of the Operclipygus impuncticollis group, especially in the small size, arrangement of pronotal striae (Fig. 101A), and coarse pygidial sulcus (Fig. 101B), although the male genitalia show sufficient differences to suggest that this is convergence. It is also similar to the following species, Operclipygus faltistrius , in several characters. Operclipygus pygidialis can be separated from the Operclipygus impuncticollis group species by the complete outer subhumeral stria and by its overall pygidial shape, which is shorter and broader, and from Operclipygus faltistrius by its small, deep propygidial punctures, and deep pygidial sulcus.