(Figs. 19, 42, 83-84, 111, 119)

Type material: Holotype ♂ (MUSM): Peru, Huanuco, provincia de Leoncio Prado, 40 km NE de Tingo Maria, Abra Divisoria, Rio Azul, 09°12′12″S, 75°48′47″, alt. 1,670 m, 04.IV.2015, leg. R. Constantin.

Description: Holotype. Length 3.5 mm. Head black, the clypeus yellow. Pronotum orange yellow. Elytra chocolate-brown. Antennae black, the first two antennomeres yellow, the third brownish yellow. Legs orange yellow, the apical half of tibiae and the tarsi brown. Abdomen brown. Head 0.86 times as wide as pronotum, short, the clypeus not protruding. Eyes remarkably developed, broad, bulging, the interocular space only as wide as one third of head width. Frons concave between the antennal sockets.Temples short. Cephalic surface smooth, not punctate,with sparse thin yellowish setae. Antennae longer than the body, the first two antennomeres smooth, the second very minute, the following parallel sided, warty, bearing numerous erect brown setae as long as antennomere width. Pronotum 1.6 times wider than long, with angular apical edge, arched and laterally sinuous basal edge, the lateral edge with a narrow bead and an emargination in front of the basal corners. Pronotal surface shiny, without visible punctation. Elytra 2.4 times longer than combined width at the base, very thinly punctate, irregularly disposed, covered with long, thin, yellow setae. Aedeagus: tegmen with apices of lateral lobes straight and dorsally emarginated; lateral sclerites long and slender; median lobe very short.

Dimensions of the holotype: TL = 3.5 mm; AL = 4.0 mm; HW = 0.86 mm; IOW = 0.3 mm; OL = 0.43 mm; IAW = 0.09mm;PL = 062 mm;PW = 1.0 mm; EL= 2.65 mm; EW = 1.1 mm. Length of the antennomeres, in mm: aI = 0.29; aII = 0.08; aIII = 0.36; aIV = 0.4; aV = 0.44; aVI = 0.45; aVII = 0.45; aVIII = 0.43; aIX = 0.39; aX = 0.33; aXI = 0.35.

Differential diagnosis: Plectonotum rubrithorax sp. nov., is similar to the Peruvian species P.neoruficolle nom. nov., by the similar habitus and colour pattern. It differs from the latter by the concave frons, broader eyes, longer antennae, narrower pronotal bead and aedeagus shape.

Etymology: The specific epithet refers to the peculiar pronotal colouration.

Natural history: Collected beating shrubs and trees on the edge of a small wood.