Megarthrus machu, 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 : 114-115

Megarthrus machu sp. n. Figs 11, 87-104

TYPE MATERIAL: Holotype (Ƌ, in SEMC): PERU, Cuzco Dept., Pillahuata, Manu Rd. , Km 128, 27.ix.1982 (Watrous & Mazurek) #82-308, ex vine litter . – Paratypes (4): same data as holotype, 1 ♀ in FMNH ; same data, but 26.ix.1982, #82-301, 2 ♀♀ in FMNH and MHNG ; same data, but 25.ix.1982, #82-290, on tent, 1 ♀ in FMNH .

DESCRIPTION: Habitus as in Fig. 11. Combined length of pronotum and elytra =

2.1-2.3 mm; maximal pronotal width = 1.5-1.6 mm. Body dark brown with appendages and elytra slightly paler; antennomeres 10-11 paler than antennomeres 1-9. Dorsal pubescence fairly uniform, denser on head and pronotum than on elytral disc; frontal setae directed forward; elytral and pronotal setae fairly straight, recumbent; metasternal pubescence fairly uniform, shorter than prosternal; pubescence on abdominal tergites parallel, becoming denser near posterior margin of tergite VII. Frons, humeral callus of elytra and anterior portion of prohypomera granulate; frontal granulation conspicuous, with granula about as high as their diameter, or higher; pronotum granulofossulate; metasternum with granulofossulation becoming denser and finer posteriomedially; elytral disc coarsely punctate.

Frons forming above clypeus a sharp ridge. the latter finely evenly carinate, weakly arcuate in middle and laterally oblique in dorsal view; mesal portion of disc strongly evenly convex lateral view; U-shaped frontal impression deep. Temples strongly convex in dorsal view. Antennae (Fig. 98) 2.3-2.6 times longer than pronotum.

Pronotum (Fig. 97) with center strongly convex in frontal view; disc deeply depressed near middle of lateral edge, shallowly depressed along anterior and posterior margins; medial groove 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 angulate in middle and posterior margin slighly arcuate toward obtusely angular apex.

Elytra abruptly widened subbasally (Fig. 11); humeral callus low, moderately convex; disc with low swellings, deeply depressed along lateral edge; the latter finely carinate, markedly denticulate, strongly arcuate in dorsal view.

Abdominal sternites II and III with medial processes as in Fig. 96, posterior portion of process of sternite III widened, or trifid.

Male: Frontoclypeal area not modified. Protarsomeres 1 lacking tenent setae. Mesofemora (Fig. 90) as long as metafemora (Fig. 89). Mesotibiae (Fig. 94) shorter than metatibiae (Fig. 95). Metatarsomeres 1 about as long as combined length of metatarsomeres 2-4. Peg-like setae arranged in a single row on mesotrochanters (Fig. 90), grouped in a field on mesotibiae and metatibiae, and absent from protrochanters, profemora, protibiae, mesofemora, metatrochanters (Fig. 89) and metafemora. Pubescence on sternites IV-VII becoming denser posteriomedially. Apex of abdominal tergite VIII as in Figs 91, 93. Sternite VIII as in Fig. 92. Sternite IX lacking subbasal protuberance. Aedeagus as in Figs 87-88.

Female: Pubescence on sternites IV-VII uniform, except for a pair of subapical macrosetae on each sternite. Abdominal tergite VIII (Figs 102-103) without medioapical projection. Sternite VIII as in Fig. 104. Genital segment as in Figs 99-101; gonocoxal plate bearing a mediodorsal ridge.

DISTRIBUTION AND NATURAL HISTORY: Megarthrus machu is know only from the type locality in Peru (Pillahuata <3° 7' S; 71° 25' W>), which is situated at an elevation of nearly 2500 m just below a patch of forest. It was found in vine leaf litter, and showed good ability to fly (one specimen was found on a tent) .

COMMENTS: Within Neotropical Megarthrus , M. machu is easily distinguished by its abruptly and broadly expanded elytra. Exceeding 4 mm in length (when measured from the middle of the frontal margin to the tip of the abdomen), it is the largest species of Proteininae of the world. See comments under M. adelphus .