Holotype (male): “BRAZIL: Pará/ Rio Xingu Camp 52°22'W, 3°39'S/ Altamira, ca 60km S.; 14.x.1986/ leg. P. Spangler & O. Flint// Colln. #23, stream on/ left branch of trail 1” (USNM). Paratype (1): BRAZIL: Pará: same, except “3.x.1986; Colln. #6;/ 1^st jungle stream on trail 1” (1, USNM).

Crucisternum xingu is very similar to C. sinuatus and C. escalera in the shallowness of the punctation and the uniform coloration along the body. It can be readily recognized by its dark brown coloration (as opposed to orange brown; compare Fig. 3E–H to Fig. 1), which is shared with C. sinuatus, from which it can be distinguished by the median lobe gradually narrowing towards the apex (see Fig. 6E, F; as opposed to constricted at midlength, continuing as a narrow and roundly pointed bar, see Fig. 6G, H), and the nearly straight to sinuate outer margins of the parameres (as opposed to strongly constricted at apical third, continuing nearly parallel).

Body length 2.2–2.4 mm, width 1.3–1.4 mm. General coloration uniformly dark brown (Fig. 3E). Elytra with punctures shallowly marked. Aedeagus with outer margins of parameres sinuate to nearly straight; inner margins of parameres concave along apical third; median lobe gradually narrowing towards apex; apex of median lobe rounded (Fig. 6E–F).

Noun in apposition. Named after the Xingu River where the known specimens were collected.

Brazil (Pará). See Fig. 7.

This species is known from forest streams.