Megarthrus bierigi, Cuccodoro & C. & P. & Ch-, 2011

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 : 111-112

Megarthrus bierigi sp. n. Figs 7, 39-56

TYPE MATERIAL: Holotype (Ƌ, in SEMC): COSTA RICA, Puntarenas, Monteverde Biol. Res., trail near lab, 1550m, 21-22.v.1993 (Michalski) ex flight intercept trap . – Paratypes (13): same data as holotype, 2 ♀♀ in MHNG and SEMC; same data, but 26-28.v.1993, 2 ♀♀ in SEMC. – Same data, but 1-2.vi.1993, 2 ƋƋ in SEMC and 1 Ƌ in MHNG. – Same data, but 1620m, 25.vi.1990 (Roberts) ex flight intercept trap, 1 ♀ in MHNG. – COSTA RICA, Alajuela, Peñ as Blancas, 1420m, 20.v.1989 (Ashe, Leschen & Brooks) #274, ex flight intercept trap, 1 Ƌ in SEMC. – San Isidro, La Estrella, 16.x.1941 (Bierig) 1 Ƌ and 3 ♀♀ in FMNH [mislabelled types of M. inaequalis Bierig ] .

DESCRIPTION: Habitus as in Fig. 7. Combined length of pronotum and elytra = 1.3-1.4 mm; maximal pronotal width = 0.9-1.1 mm. Body dark brown with appendages slightly paler; antennomeres 11 paler than antennomeres 1-10. Dorsal pubescence fairly uniform, denser on head and pronotum than on elytral disc; frontal setae directed forward; elytral and pronotal setae slightly arcuate, recumbent; metasternal pubescence fairly uniform, as long as or longer than that of prosternum; pubescence on abdominal tergites parallel, uniform; 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, the latter finely carinate, weakly arcuate in middle and laterally oblique in dorsal view; mesal portion of disc strongly evenly convex in lateral view; U-shaped frontal impression deep in middle, shallow laterally. Temples strongly convex in dorsal view. Antennae (Fig. 51) 2.3-2.5 times longer than pronotum.

Pronotum (Fig. 56) with center strongly convex in frontal view; disc deeply depressed near middle of lateral edges, shallowly depressed along anterior margin, 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, with a discal pit. Prosternal medial ridge absent. Scutellum with anterior margin rounded and posterior margin slighly arcuate toward acutely angular apex.

Elytra gradually widened (Fig. 7); humeral callus raised, forming a blunt longitudinal ridge; disc with low swellings, moderately depressed posteriorly along lateral edges; the latter finely carinate, indistinctly denticulate, slightly arcuate in dorsal view.

Abdominal sternites 2 and 3 with medial processes as in Fig. 54, posterior portion of process of sternite 3 widened.

Male: Frontoclypeal area not modified. Protarsomeres 1 lacking tenent setae. Mesofemora (Fig. 43) as long as metafemora (Fig. 45). Mesotibiae (Fig. 42) shorter than metatibiae (Fig. 43). Metatarsomeres 1 about as long as combined length of metatarsomeres 2-4. Peg-like setae arranged in a single row on mesotrochanters (Fig. 43), 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 44, 47. Sternite VIII as in Fig. 46. Sternite IX lacking subbasal protuberance. Aedeagus as in Figs 39, 40.

Female: Abdominal tergite 8 (Figs 53, 55) lacking a medioapical projection. Sternite VIII as in Fig. 52. Genital segments as in Figs 48-50; gonocoxal plate bearing a mediodorsal ridge.

ETYMOLOGY: The species is named after its first collector, Alejander A. Bierig,

San Pedro de Montes de Oca.

DISTRIBUTION AND NATURAL HISTORY: The species is apparently restricted to Costa Rica, where it was collected at elevations ranging from 1400-1600 m using flight intercept traps.

COMMENTS: From the Neotropical Megarthrus possessing a conspicuous humeral callus ( M. bierigi , M. inaequalis and M. mammiger ), M. bierigi can be easily distinguished by its lack of elytral discal humps. See comments under M. adelphus .