Arthrobrachus forsteri Wittmer 1958

Arthrobrachus forsteri Wittmer, 1958.

(Figure 1 –3)

Holotype: La Paz, Bolivia. 7625. Deposited in Zoologische Staatssammlung München in Munich, ♂.

Diagnosis. Antennae with four dilated preapical antennomeres (Fig. 1,2a); pronotum with an anterolateral, oblique carina, half the length of the pronotum; the lateral margins of the protonum have flattened, slightly widened and curved planes; males: ventrite 6 with two flat, transverse, subcontiguous plates (Fig. 2b); last tergite rounded apically (Fig. 2b); parameres are weakly sclerotized at the base; apex is subsquare in dorsal and ventral view (Fig. 3a,b); tegmen has no dorsal flange at the base of the parameres; tegminal plate is reduced and flat, slightly projected on apodeme (Fig. 3c); tegminal arms are curved, (Fig. 3c); dorsal surface of the median lobe is sclerotized, with no flection area (Fig. 3d,e).

Description: Male: body length 4 mm (Fig.1), length: width ratio as 1.6:1, sides subparallel; pronotum and elytra with distinct coarse punctures covering their dorsal surface; fine, short and inclined pubescence, dense on dorsal surface; dark-testaceous body, elytra with a light testaceous marginal stripe, also slightly curved and extended to the suture before the apex; orange antennae and legs.

Head: Including the eyes, slightly wider than the distal margin of the pronotum (1.12:1); antennae shorter than the length of the pronotum (0.866:1), with the seventh to tenth antennomer dilated (Fig. 1,2a).

Thorax: Pronotum wider than it is long (1.5:1), moderately convex transversely and slightly curved longitudinally, with base as wide as the apex (1:1) and narrower than the humeral region (0.7:1); from a dorsal view, the distal margin is slightly convex, distal and basal margins are well marked, lateral margins are flattened and slightly curved; the oblique lateral carina extends from the anterior margin up to almost half the length of the pronotum and is more marked on the distal part. Elytra length: width ratio 1.34:1; subparallel lateral margins in the two basal thirds and rounded in the distal one; disc moderately convex, with light lateral border; wide, grainy and hairy epipleura with no apical denticles. Legs: median and hind tibiae with scarce and small spines in the external margin, tarsomeres with few ventral spines.

Abdomen: Ventrite 5 with straight distal margin, slightly concave; ventrite 6 with two flat transverse subcontiguous plates; last tergite has a rounded distal margin and rounded distal angles (Fig. 2b); segment 9 weakly sclerotized, tergum narrow, fine sternal arms and moderately short apodeme (Fig. 2c). Genitalia: parameres subsquare at apex and slightly emarginated in the middle, sides subparallel, emarginated or weakly sclerotized at the base, lateral margins communicated on the apex. Tegmen has no dorsal flange at the base of the parameres; thick tegminal arms with curved sides, gradually convergent toward the base, from lateral view, curved; tegminal plate plane, curved from a lateral view; distal margin slightly concave; apodeme is subtriangular (Fig. 3a–c). Median lobe body, subcylindrical, sclerosed, with sides subparallel, converging at apex; from lateral view, slightly curved; no flection area at base; apex acuminate; phallotreme oblong, with a linear membranous area; apodeme is enlarged (Fig. 3d–f).

Distribution: BOLIVIA: Departamento de La Paz, Province of Pedro Domingo Murillo, La Paz (3.600 – 4.000 msnm) (ZSM). ARGENTINA: Province of Formosa, Clorinda (IMLA) (1♂).