Megarthrus flavosignatus Bierig, 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 : 112-113

Megarthrus flavosignatus Bierig, 1940 Figs 5, 57-68

Megarthrus flavosignatus Bierig, 1940: 378 .

TYPE MATERIAL: Holotype (Ƌ, in FMNH): “ Carpintera , 6.viii.39, Costa Rica [handwritten] | Typus ”.

ADDITIONAL MATERIAL: Same data as holotype, but 16.vi.1940, 1 Ƌ in MHNG.

DESCRIPTION: Habitus as in Fig. 5. Combined length of pronotum and elytra = 1.3-1.4 mm; maximal pronotal width = 0.9-1.1 mm. Body dark brown wih appendages slightly paler; antennomeres 10-11 paler than antennomeres 1-9. Dorsal pubescence denser on head and pronotum than on elytral disc, becoming denser along medial groove of pronotum and on anterior portion of elytral disc; frontal setae directed forward; elytral and pronotal setae slightly arcuate, recumbent; metasternal pubescence becoming denser anteriorly and medially, as long as or longer than that of prosternum; pubescence on abdominal tergites parallel, uniform; that on sternites IV-VIII uniform. Frons, pronotum, lateral portion of elytral disc and anterior portion of prohypomera granulate; frontal granulation conspicuous, with granula about as high as their diameter, or higher; central, adsutural and posterior area of elytral disc punctate, coarsely; metasternum coarsely granulofossulate.

Frons forming above clypeus a sharp ridge, the latter finely evenly carinate, nearly straight in middle and laterally oblique in dorsal view; mesal portion of disc strongly evenly convex in lateral view; U-shaped frontal impression shallow. Temples strongly convex in dorsal view. Antennae (Fig. 61) 2.1-2.3 times longer than pronotum.

Pronotum (Fig. 68) with center strongly convex in frontal view; disc deeply depressed near middle of lateral edges, shallowly depressed along anterior and posterior margins; medial groove slightly arcuate in lateral view, deep, narrowed in middle; hypomera ridged from anterior margin to laterobasal angle, disc without pit. Prosternal medial ridge absent, or absent. Scutellum with anterior margin rounded and posterior margin slighly arcuate toward right-angled apex.

Elytra gradually widened (Fig. 5); humeral callus low, moderately convex; disc with low swellings, moderately depressed posteriorly along lateral edges; the latter very finely carinate, finely denticulate, slightly sinuate in dorsal view.

Abdominal sternites II and III with medial processes as in Fig. 66, posterior portion of process of sternite III straight.

Male: Frontoclypeal area not modified. Protarsomeres 1 lacking tenent setae. Mesofemorar (Fig. 62) as long as metafemora. Mesotibiae (Fig. 60) shorter than metatibia (Fig. 59). Metatarsomere 1 about as long as combined length of metatarsomeres 2-4. Peg-like setae arranged in a single row on mesotrochanters (Fig. 62) and mesotibiae, arranged in double row on metatibiae, and absent from protrochanters, profemora, protibiae, mesofemora, metatrochanters and metafemora. Apex of abdominal tergite VIII as in Figs 63, 67. Sternite 8 as in Figs 64-65. Sternite IX lacking subbasal protuberance. Aedeagus as in Figs 57-58.

Female: Unknown.

DISTRIBUTION AND NATURAL HISTORY: The species is known only from the type locality in Costa Rica. According to the original description, A. Bierig collected the holotype at 1800 m from sifted leaf litter of a fallen tree in forest (together with the types of M. adelphus ) .

COMMENTS: The male abdominal sternite VIII with a pair of projecting tips of M. flavosignatus is particularly notable. This feature is shared only with M. zunilensis , which has different male sexual characters. See comments under M. zunilensis .