Operclipygus quadratus, Caterino, Michael S. & Tishechkin, Alexey K., 2013

Caterino, Michael S. & Tishechkin, Alexey K., 2013, A systematic revision of Operclipygus Marseul (Coleoptera, Histeridae, Exosternini), ZooKeys 271, pp. 1-401 : 94-98

Operclipygus quadratus sp. n. Figs 24 E–F25A–DMap 8

Type locality.

BRAZIL: Pará: Tucuruí [3°45'S, 49°40'W].

Type material. Holotype male: "BRASIL: Pará: Tucuruí, 3°45'S, 49°40'W. Piège d’interception. vi.1985"/ "Caterino/Tishechkin Exosternini Voucher EXO- 00287 " (UFPR). Paratypes (6): 1: same data as type (CHND); FRENCH GUIANA: 1: Belvèdére de Saül, point de vue, 3°1'22"N, 53°12'34"W, 20.xii.2010, FIT, SEAG (FMNH), 1: 4.i.2011, FIT, SEAG (MNHN); 1: Rés. Natur. des Nouragues, Camp Inselberg, 4°05'N, 52°41'W, 22.viii.2011, FIT, SEAG (CHND), 1: 25.viii.2011, FIT, SEAG (MSCC). 1: GUYANA: Kurupukari, 4°40'N, 58°40'W, ix–xi.1992, malaise/FIT (BMNH).

Other material.

BRAZIL: 2: Mato Grosso: Claudia, 11°24.5'S, 55°19.5'W, 17-27.x.2010, FIT, A.F. Oliveira (MSCC, FMNH); 1: Cotriguaçu, Fazenda São Nicolau, Mata Norte, 9°49.15'S, 58°15.6'W, 8-14.xii.2010, FIT, F.Z. Vaz-de-Mello (CEMT); Pará: 2: Tucuruí, 3°45'S, 49°40'W, vi.1985, FIT (CHND, AKTC).

Diagnostic description.

Length: 1.93-2.00 mm, width: 1.34-1.56 mm; body rufobrunneus, broad, depressed, subquadrate, densely punctate on all surfaces; frons depressed at middle, frontal stria divergent, rounded between eyes, complete, transverse across front, continuous with complete supraorbital stria; epistoma broadly depressed, elevated at sides and along apical margin; labrum about half as long as wide, with sides rounded, apex shallowly emarginate; left mandible with prominent, acute basal tooth, right mandible untoothed, with apex frequently narrow, elongate; prono tal disk with indistinct prescutellar impression; marginal stria interrupted behind head; lateral submarginal pronotal stria complete, very close to margin, subcarinate, curving inward at front, meeting anterior submarginal stria at distinct postocular angulation; anterior submarginal stria transverse, ends not recurved posterad; median pronotal gland openings within postocular angulation of striae; elytra with all striae impressed as pair of dense rows of interconnected punctures; one complete epipleural stria present, outer subhumeral complete beneath strong lateral elytral margin (apparently representing complete inner subhumeral stria), dorsal striae 1-5 complete, sutural stria and marginal carina connected by a complete, fine apical marginal stria; prosternal keel produced posteriorly, truncate at base, carinal striae deeply impressed, meeting at acute angle in front; prosternal lobe with midline elevated, apex distinctly, narrowly emarginate, marginal stria interrupted by emargination; mesoventrite deeply emarginate anteriorly, marginal stria interrupted by anteriorly arched, deeply impressed, crenulate mesometaventral stria; lateral metaventral stria reaching middle of metacoxa; 1st abdominal ventrite with two complete lateral striae; propygidium and pygidium similarly densely, uniformly covered with small punctures; marginal pygidial sulcus complete, fine. Male genitalia (Fig. 25): accessory sclerites absent; T8 rather short, sides moderately convergent to apex, basal apodemes rounded, basal emargination subangulate, basal membrane attachment line distad emargination by about one-third its depth, ventrolateral apodemes most strongly produced at middle, nearly meeting at midline, apical emargination simple; S8 very much like Operclipygus hospes , sides broadly rounded in basal two-thirds, apical guides narrow, only developed near apex, ventrally halves approximate for short distance near base, weakly diverging to apex; T9 with sides in contact for short distance along dorsal midline, apices narrow, truncate; T10 divided; S9 narrowest just basad middle, basal half strongly widened, broadly rounded, largely desclerotized, lateral flanges with prominent apical corners, apex with narrow, shallow median emargination, apical flanges small and separate; tegmen rather narrow, elongate, widest just distad midpoint, narrowed to base, apex subacute, with subapical, ventrolateral cleft, medioventral process long with very narrowly truncate apex projecting beneath about one-third from base; basal piece about one-third tegmen length; median lobe about one-third tegmen length, with filamentous portions of proximal apodemes not apparent.

Remarks.

This species is generally very similar to Operclipygus carinisternus , but can be separated by the angulate junction of the anterior and lateral submarginal pronotal striae behind the eye (Figs 24 E–F). Operclipygus quadratus also lacks a recurrent stria on the lateral part of the metaventrite, which all the other species in the group have. While this species is highly distinctive, there is also a surprising amount of variation in several significant characters. In particular, a few individuals have mandibles with the apex of the incisor edge strongly prolonged and narrowed (Fig. 24F), and this might appear to represent sexual dimorphism. However, some males do not show this, even from the same locality as the holotype. So it seems to represent a more complex within-species polymorphism. Other variable characters include the degree of frontal depression, the depth of the prosternal lobe emargination, the size of elytral interstrial punctures, and presence of elytral microsculpture. We therefore delimit the type series very narrowly, in case this turns out to be a complex of closely related species.

Operclipygus quadratus shares significant characters with members of the Operclipygus hospes group, including the deeply emarginate mesoventrite with arched mesometaventral stria, the two complete lateral striae on the 1st abdominal ventrite, the basally rounded S8 and by the shape of the tegmen and its ventral subapical cleft, and it may represent a transitional form linking the two groups, although phylogenetic analyses do not support this idea unambiguously.

Etymology.

The name of this species refers to its distinctly quadrate body form.