Holotype, male (Fig. 30a). Length 2.24 mm. Color of antennae and tarsi ferruginous; remainder dark ferruginous to black; elytra with slight bronze lustre. Body subovate, in dorsal aspect and in profile with weak constriction between pronotum and elytron. Rostrum with median ridge and pair of submedian ridges, intervening furrows each with sparse row of mesad directed scales; epistome with transverse subangulate ridge. Pronotum coarsely punctate, interspaces longitudinally rugose; with median costa; with sparse, suberect scales. Elytra with striae deeply impressed, each with row of slender suberect scales; intervals costate, subglabrous; in basal half incised suture bordered by row of punctures. Femora with simple, crenate anteroventral ridge. Metafemur subapically with stridulatory patch. Metatibia apically with uncus, without premucro. Abdominal ventrite 5 flat, coarsely punctate. Penis (Fig. 30b) with sides of body subparallel; apex broadly angulate, medially rounded and sparsely setose; in apical third with pair of elongate sclerites converging to orifice; transfer apparatus compact, symmetrical; apodemes 1.8 × as long as body; ductus ejaculatorius without bulbus. Intraspecific variation. Length 2.18–2.24 mm. Female unknown.

Holotype (MZB): ARC2192 (EMBL # LM655648), East Nusa Tenggara Prov., Flores Isl., Ruteng, Danau Ranamese, sample 1, S08°37.705', E120°33.702', 1320 m, 08-III-2011. Paratypes (SMNK): Flores Isl., Ruteng, Mt. Ranaka: 1 ex, ARC2583 (EMBL # LM655892), sample 9, S08°37.641', E120°31.204', 1685 m, 10-III-2011.

East Nusa Tenggara Prov., Flores (Ruteng). Elevation: 1320–1685 m.

This epithet is based on the Indonesian word for “four” and is treated as a noun in apposition.

Trigonopterus empat Riedel, sp. n. was coded as “Trigonopterus sp. 303” by Tänzler et al. (2014).