Trigonochrostia Hampson

Type species: excisa Hampson, Borneo.

This is a monobasic genus where only the holotype female of the type species is known. It is a small, dull, greyish brown insect with narrow forewings that are paler (or more worn!) over the basal two thirds. They are crossed by very broken black antemedial and postmedial fasciae that are most clearly marked on the costa. The hindwings are rather triangular, uniformly dark, the same shade as the distal part of the forewings. The forewing venation resembles that of Neachrostia with R1 and R2 arising independently from the cell; the remaining radial sector veins are reduced from  three to two and are stalked. In the hindwing, all veins are present; Rs and M1 are stalked, and M3 and CuA1 are connate.

The labial palps are directed forward, the second segment triangular, broadest at the junction with the third which is half the length, much narrower and slightly downturned. The lower clypeofrons is unscaled.

The female genitalia have the eighth segment very short, the ostium at its anterior margin with a distinctly convex underlip extending from the short, sclerotised basal portion of the ductus bursae. The distal part of the ductus bursae is twice as long as the basal part but narrower, unsclerotised, and joins the corpus bursae subbasally. The basal lobe of the corpus bursae is rounded and gives rise to the ductus seminalis before narrowing into a much narrower but longer section that broadens just basal to central into the pyriform distal part of the bursa. This last contains a narrow scobinate band that extends obliquely for most of its length.