Megarthrus solitarius Sharp, 1887

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 : 119-120

Megarthrus solitarius Sharp, 1887 Figs 3, 154-170

Megarthrus solitarius Sharp, 1887: 743 .

TYPE MATERIAL: Holotype (♀, in BMNH): “ Megarthrus solitarius . Type D. S. Purula, Guatemala, Champion [Sharp’s handwritting] / Purula, Vera Paz, Champion / B.C.A. Col. 1. 2. Megarthrus solitarius Sharp ”.

ADDITIONAL MATERIAL: GUATEMALA, Bja Verapaz , 8km S Purulhá, 1650m 29.vi.1993 (Ashe & Brooks) #149, ex Cecropia treefall , 2 ƋƋ and 2 ♀♀ in MHNG and SEMC .

DESCRIPTION: Habitus as in Fig. 3. Combined length of pronotum and elytra = 1.3-1.5 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 fairly uniform, denser on pronotum than on elytra; frontal setae directed forward; elytral and pronotal setae slightly arcuate, recumbent; metasternal setae uniform, shorter than prosternal; pubescence on abdominal tergites parallel; that on sternites IV-VII uniform, except for a pair of subapical macrosetae on each sternite. 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 evenly carinate, 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. 165) 2.1-2.3 times longer than pronotum.

Pronotum (Fig. 169) with center moderately convex in frontal view; pronotal disc deeply depressed near middle of lateral edges, shallowly depressed along anterior margin, posterior margins 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 absent. Scutellum with anterior margin subangulate in middle and posterior margin weakly arcuate toward right-angled apex.

Elytra gradually widened (Fig. 3); humeral callus low, moderately convex; disc with low swellings, moderately depressed posteriorly along lateral edge, the latter finely carinate, very finely denticulate, in dorsal view slightly arcuate.

Abdominal sternites II and III with medial processes as in Fig. 170, posterior portion of process of sternite III widened, or trifid.

Male: Frontoclypeal area not modified. Protarsomeres 1 lacking tenent setae. Mesofemora (Fig. 158) as long as metafemora. Mesotibiae (Fig. 159) shorter than metatibiae. Metatarsomeres 1 about as long as combined length of metatarsomeres 2-4. Peg-like setae arranged in a single row on mesotrochanters (Fig. 158), grouped in a field on mesotibiae, and absent from protrochanters, profemora, protibiae, mesofemora, metatrochanters, metafemora and metatibiae. Apex of abdominal tergite VIII as in Figs 156, 157. Sternite VIII as in Figs 160-161. Sternite IX lacking subbasal protuberance. Aedeagus as in Figs 154, 155.

Female: Abdominal tergite VIII (Figs 166-167) with a medioapical projection. Sternite VIII as in Fig. 168. Genital segments as in Figs 162-164; gonocoxal plate bearing a mediodorsal ridge.

DISTRIBUTION AND NATURAL HISTORY: Megarthrus solitarius is apparently endemic to Guatemala (Dept de Baja Verapaz), where it was collected in Cecropia treefall at an elevation of 1650 m.

COMMENTS: Megarthrus solitarius and M. zunilensis are apparently the only Neotropical Megarthrus with the abdominal tergite VIII forming a medioapical projection in the female. These two species differ, however, in most of the other sexual characters. See discussion under M. ogloblini .