Macrostomus acreanus sp. nov.

(Figs 1–9, 54–55)

Diagnosis. Thorax predominantly black, except mesopleuron yellow adjacent to all coxae. Abdomen including terminalia black. Male tergite 8 short, with shallow sinus anteriorly and indistinct sinus posteriorly. Anterior cercus longitudinally elongate; posterior cercus vertically elongate, simple, inverted C-shaped. Hypandrium with uniseriated setae medially. Female hind tibia without pinnate setae.

Description. Holotype male. Body length 2.7 mm; wing length 2.9 mm. Width of frons approximately subequal to anterior ocellus width. Antenna velvety black. Palpus brown. Thorax shiny black with mesopleuron adjacent to all coxae yellow. Thoracic setae: 3–4 dorsocentrals, 2–3 antepronotals, 1–3 proepisternals, 1–2 pairs of scutellars. Legs shiny yellow with apex of hind femur, entire hind tibia and all tarsi black, except fore tarsomeres 1–2 somewhat yellow. Hind femur (Fig. 1) with setae as described for species-group. Wing (Fig. 54, paratype). Halter dark brown, knob partially white. Abdomen shiny black. Terminalia with tergite 8 short, with shallow sinus anteriorly and indistinct sinus posteriorly (Fig. 2). Epandrium with anterodorsal and posterodorsal lobes of same height (Fig. 3). Anterior cercus longitudinally elongate; posterior cercus elongate vertically, simple, somewhat inverted C-shaped. Cercal bridge (Fig. 4) that connects both anterior cerci, almost as long as, and connected anteriorly to, anterior cercus. Ventral projection of cercus thin, without setae distally. Hypandrium (Fig. 5) bearing aligned uniseriated setae medially, with small sinus on posterior margin distad of last seta.

Female. Hind tibia without pinnate setae. Wing (Fig. 55). Terminalia (Figs 6–9). Tergite 8 slightly shorter than sternite 8 (Fig. 6) with distal sinus larger than basal one (Fig. 7). Sternite 8 (Fig. 8) slightly wider at basal third. Genital fork (Fig. 9) small with elongated inwardly curved lateral arms. Genital chamber membranous.

Geographical distribution. Brazil (Acre).

Type Material. HOLOTYPE ♂: “ BRASIL, Acre, Cruzeiro do Sul, Rio Moa, 0 7 º 37'02''S – 72 º 46'15''W, 19– 28.xi.1996 ”; “J.A.Rafael, J.Vidal & R.L.Menezes” [sweeping, forest]; “ Macrostomus acreanus Holótipo ♂” (red label) (INPA). PARATYPES. BRAZIL. Same data as holotype (3♂, 1♀ INPA; 3♂, 1♀ CNC).

Holotype condition. Pinned, in good condition, not dissected.

Etymology. Named after the Brazilian State, Acre, where the specimens were collected.

Discussion. Macrostomus acreanus sp. nov. differs from other species in the species-group by the male having a cercal bridge (Fig. 4) that is almost as long as the anterior cercus (shorter in other species), a hypandrium (Fig. 5) with a narrow posterior sinus (wide or absent in other species), a longitudinally elongate anterior cercus (in lateral view), and a vertically elongate simple posterior cercus that is inverted C-shaped (Fig. 3).