Tribonium sagittum sp. nov.

(Figs. 1–8)

Coloration mainly brown with darker spots (Fig. 8). Light-yellow ocellar spots. Dark-brown eyes and vertex; clypeus with brown labrum and chestnut-brown spots evident on apex (Fig. 1). Pronotum brown with symmetrical dark spots, without a defined shape in central region (Fig. 2). Anal base of tegmen chestnut-brown. Marginal field of tegmen and outer part of scapular field varying from brown to light brown. Whitish-brown pulvilli; light-brown arolium and claw with darker apical portion.

Measurements of holotype male (mm): total length 16.0; pronotum length 3.0; pronotum width 6.0; tegmen length 13.5; tegmen width 4.0.

Head triangular; vertex exposed; interocular space broad, 0.8 mm wide, approximately half the distance between antennal sockets. Well-marked ocellar spots. Antennae of medium length, not reaching apex of tegmina. Palpi and antennae hairy; second article of maxillary palp minute, third article about 0.5 mm long, fourth article same size as second, fifth article enlarged similarly to third article and markedly tomentose.

Pronotum convex, with apical region on head in relief with rounded border. Tegmina developed, extending beyond apex of cerci; marginal field slightly concave, apex blunt in dorsal view; scapular field tapering progressively to apex; discoidal field extended mid-apically, slightly angular along the veins. Wings with narrow marginal field, subcostal vein reaching basal third of scapular field; cubital vein with numerous complete veins and fewer incomplete veins; apex triangle absent. Legs short, robust; anterior, middle, and posterior legs narrow, with slight projection on the inner apex of posterior coxae. Fore, mid, and hind femora sparsely ciliate along ventro-cephalic margin. Small pulvilli present on four tarsal segments; claw simple, symmetrical, with concave arolium.

Supra-anal plate setose, with prominent median edge between the cerci with slight median indentation; cerci short, setose, with 11 segments (Fig. 3). Right phallomere hook-shaped, with small preapical indentation (Fig. 4). Subgenital plate asymmetrical, with two tapered styles, derived from edges of plate (Fig. 5). Median sclerite elongated preapically, with lateral arm; apex of median sclerite irregular and slightly rounded, arrow-shaped, with lateral expansions differentiated in size and shape (Fig. 6); left phallomere slightly sclerotized (Fig. 7).

Etymology. The name “ sagittum ” derives from the Latin sagitta, meaning arrow, referring to arrow-shaped apex of the median sclerite.

Discussion. Tribonium sagittum sp. nov. is separated from other members of the genus by the pronotum coloration and configuration of the apex of the median sclerite.

Examined material. Holotype male: Brazil, Amazonas, Coari, Urucu River, LUC-18 (4º 53’ 53”S / 65º 11’ 58”W), 19 February 1993, P. F. Buhrnheim, N. O. Aguiar, colls.