Macrostomus amazonensis sp. nov.

(Figs 18–28, 58–59)

Diagnosis. Thorax entirely black, all coxae yellow. Abdomen including terminalia black. Male tergite 8 short, with shallow sinus anteriorly and deeper sinus posteriorly. Hypandrium with many paired setae medially and with acutely pronounced sinus on posterior margin. Female hind tibia with pinnate setae.

Description. Holotype male. Body length 2.6 mm; wing length 2.7 mm. Width of frons approximately ¾ anterior ocellus width. Antenna velvety black. Palpus brown. Thorax shiny black. Thoracic setae: 3–4 dorsocentrals, 3–4 antepronotals, 1–3 proepisternals, 2 pairs of scutellars. Legs shiny, predominantly yellow with apex of mid and hind femora, apex of fore and mid tibiae black; hind tibia and all tarsi black. Hind femur (Fig. 18) with 1 anteroventral seta at distal third. Wing (Fig. 58, paratype). Halter light brown, knob partially white. Abdomen shiny black. Terminalia with tergite 8 short, with shallow sinus anteriorly and deeper sinus posteriorly (Fig. 19). Epandrium with anterodorsal and posterodorsal lobes of same height (Fig. 20). Anterior cercus subquadrate in lateral view; posterior cercus elongate vertically with secondary protuberances (Fig. 20). Cercal bridge (Fig. 21) small, connected with projection arising anteriorly from dorsal margin of anterior cercus. Ventral projection of cercus thin, with setae distally (as in Fig. 12 of M. albicaudatus). Hypandrium (Fig. 22) bearing many paired setae medially, basal pair longer, with sinus on posterior margin forming acute protuberance.

Female. Legs yellow to dark brown with coxae, trochanters and base of femora light yellow. Mid tibia (Fig. 23) with 1 slightly longer posterodorsal seta near middle. Hind tibia (Fig. 24) with longer pinnate setae along dorsal margin and shorter pinnate setae along basal third ventrally. Wing (Fig. 59). Terminalia with tergite 8 and sternite 8 almost same length (Fig. 25). Sternite 8 with cleft laterally, near middle (Figs 25, 27). Genital fork (Fig. 28) small, without lateral arms. Genital chamber slightly sclerotized.

Geographical distribution. Guyana, Brazil (Roraima, Amazonas, Pará, Rondônia, Mato Grosso).

Type Material. HOLOTYPE ♂: “ BRASIL, Am[azonas], Pq [Parque] Nac[ional] [do] Jau, Rio Unini, Democracia, 0 1 º 43'54''S – 61 º 54'32''W, 2–24.vi.1996 ”; “A.L.Henriques, J.Vidal & F.L.Oliveira, varredura”; “ Macrostomus amazonensis Holótipo ♂” (red label) (INPA). PARATYPES. BRAZIL. Same data as holotype (2♂, 2♀ INPA, 2♂, 1♀ CNC); Amazonas, Rio Jau, Meriti, Novo Airão, 4–10.vi.1994, J.A. Rafael (1♂, 2♀ INPA; 1♂, 2♀ CNC); Tabatinga, 11–14.vii.1991, Socorro & Vidal (1♂, 1♀ INPA); Tefé, 15.vii.1991, Rafael & Vidal, varredura (3♂, 3♀ INPA; 1♂, 1♀ CNC); S. Izabel do Rio Negro, Maturacá, 11–13.x.1990, J.A. Rafael, arm. Malaise (1♂, 1♀ INPA; 1♂, 2♀ CNC); Roraima, Pacaraima, 5–8.iii.1988, Eq. J.A. Rafael, arm. Malaise, mata (1♂ INPA); Serra Pacaraima, BR 174, 0 4 º 27'04''N 61 º 07'56''W, varredura, J.A.Rafael & J.Vidal (2♀ INPA); Mato Grosso, 12 º 50'S 51 º 47'W, 20.iii.1968, O. W. Richards, R.S & R.G.S. Exped., B.M. 1968–260, swarm over log, dry forest (3♂, 5♀ BMNH); Rondônia, Ouro Preto do Oeste, Rio Boa Vista, 6–12.vii.1995, varredura, J.A. Rafael & J. Vidal (1♂ INPA); Pará, Serra Norte, Fofoca, 18.v.1984, T. Pimentel (1♀ MPEG). GUYANA. Colls. Richards & Smart, B.M. 1937–776, Mazaruni, high forest, 20.viii.1937 (1♀ BMNH).

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

Etymology. In reference to the wide distribution in the Amazon Basin.

Variation. Two paratypes with 1 pair of scutellar setae.

Discussion. Macrostomus amazonensis sp. nov. appears most closely related to M. paraiba sp. nov. based on the cercal bridge of the male (Figs 21, 32) being connected to a projection that arises anteriorly from the dorsal margin of the anterior cercus (cercal bridge connected at ventral margin of anterior cercus in other species), the female bearing pinnate setae on the hind femur (Figs 24, 34), female sternite 8 with a lateral cleft near middle (Figs 27, 37), a small genital fork without lateral arms, and a slightly sclerotized genital chamber (Figs 28, 38).