Trigonopterus asper

The beetle is 2.48–2.60 mm long. It has a reddish-brown head and legs, with the rest of the body being black. The body is elongated, with a pronounced constriction between the pronotum and elytron when viewed from above, and a distinct narrowing also visible in profile. The rostrum is coarsely wrinkled and punctured, featuring a median ridge and a pair of irregular submedian ridges. The epistome has a faint, angled transverse ridge.^[1]

The pronotum narrows clearly near the tip and projects slightly at the front. Its surface is rough, with each puncture bearing an erect seta, and a central ridge runs along the middle. The elytra have deeply impressed striae, each lined with stout, suberect bristles. The intervals are tuberculate, mostly bare, with the sutural interval extending slightly at the apex. Interval 7 is swollen near the tip and projects weakly outward. The femora are edentate. The metafemur has a stridulatory patch near the tip. Abdominal ventrite 5 is flat, densely punctured, and covered with setae.^[1]

The penis is flattened and strongly curved in profile, with nearly parallel sides from above. The apex has a central, triangular extension. The transfer apparatus is flagelliform and 1.5 times the length of the penis body. The apodemes are 2.6 times as long, and the ductus ejaculatorius lacks a bulbus.^[1]

In females, the rostrum has pairs of lateral and submedian grooves on the upper surface, and the epistome is simple.^[1]

Trigonopterus asper is endemic to the Indonesian province of West Java, where it is known only from Mount Bukittinggul. It has been recorded from elevations of 1,983–2,185 m (6,506–7,169 ft).