Megarthrus ogloblini Bruch, 1940

Cuccodoro, Giulio, 2011, Revision of the Neotropical types of Megarthrus Curtis, 1829 and description of two new species from Costa Rica and Peru (Coleoptera, Staphylinidae, Proteininae), Revue suisse de Zoologie 118 (1), pp. 107-147 : 118-119

Megarthrus ogloblini Bruch, 1940 Figs 4, 143-153

Megarthrus ogloblini Bruch, 1940: 113 .

TYPE MATERIAL: Holotype (Ƌ, in MLPA): “ Loreto , Misiones, Rep. Argentina, Dr. A.A. Ogloblin [typewritten], 15.v.1934 [handwritten underneath the label] / Megarthrus ogloblini Bruch [handwritten], C. Bruch determ. 1939 [typewritten] / Museo La Plata [typewritten] / Typus! [handwritten]”.

DESCRIPTION: Habitus as in Fig. 4. Combined length of pronotum and elytra = 1.5 mm; maximal pronotal width = 1.0 mm. Body dark brown wih appendages somewhat paler; antennomeres 10-11 slightly paler than antennomeres 1-9. Dorsal pubescence fairly uniform, denser near lateral margin of elytra and somewhat longer anteriomedially on pronotum; frontal setae directed forward; elytral and pronotal setae slightly arcuate, recumbent; metasternal pubescence uniform, as long as or longer than that of prosternum; pubescence on abdominal tergites parallel; that on sternites IV-VII uniform. Frons, pronotum, elytra and anterior portion of prohypomera granulate; frontal granulation conspicuous, with granula about as high as their diameter, or higher; metasternum with granulofossulation becoming denser and finer posteriomedially.

Frons forming above clypeus a sharp ridge finely evenly carinate, the latter evenly arcuate in dorsal view; mesal portion of disc weakly evenly convex in lateral view; U-shaped frontal impression deep in middle, shallow laterally. Temples strongly convex in dorsal view. Antennae (Fig. 145) 2.4 times longer than pronotum.

Pronotum (Fig. 147) with center strongly convex in frontal view; disc deeply depressed near middle of lateral edges, shallowly depressed along posterior margin and posterior portion of medial groove; the latter slightly arcuate in lateral view, deep, parallel-sided; hypomera ridged from anterior margin to laterobasal angle, disc without pit. Prosternal medial ridge entire. Scutellum with anterior margin subangulate in middle and posterior margin broadly arcuate toward right-angled apex.

Elytron gradually widened (Fig. 4); humeral callus low, moderately convex; disc with low swellings, shallowly depressed posteriorly along lateral edge, the latter finely carinate, indistinctly denticulate, slightly arcuate in dorsal view.

Abdomal sternites II and III with medial processes similar to that in Fig. 20, posterior portion of process of sternite III widened.

Male: Frontoclypeal area not modified. Protarsomeres 1 lacking tenent setae. Mesofemora (Fig. 152) shorter than metafemora (Fig. 153). Mesotibiae (Fig. 148) shorter than metatibiae (Fig. 149). Metatarsomeres 1 about as long as combined length of metatarsomeres 2-4. Peg-like setae arranged in two rows on mesotrochanters (Fig. 152), grouped in a field on mesotibiae and metatibiae, and absent from protrochanters, profemora, protibiae, mesofemora, metatrochanters and metafemora. Apex of abdominal tergite VIII as in Figs 150-151. Sternite VIII as in Fig. 146. Sternite IX lacking a subbasal protuberance. Aedeagus as in Figs 143-144.

Female: Unknown.

DISTRIBUTION AND NATURAL HISTORY: Megarthrus ogloblini is known only from the type locality in Argentina (Loreto <27° 18' S; 55° 32 W>), which lies at an elevation of nearly 200 m, near the Rio Paraná. Megarthrus ogloblini is the only Neotropical member of the genus collected below 1400 m. It is also the southernmost record of a species of Proteinini in the New World.

COMMENTS: Megarthrus ogloblini differs from the other Neotropical Megarthrus , except for M. solitarius , by the shape of the pronotum, which is shallowly emarginate laterobasally and has the lateral contours forming four denticles. It can be easily distinguished from M. solitarius by the sexual characters.