Semnostoma barathrota is a moth of the family Gelechiidae.

The forewings are dark fuscous with a whitish blotch along the basal fourth of the dorsum and a grey-whitish blotch, white on the anterior edge, extending along the posterior half of the dorsum and termen to near the apex, widest above the tornus, where it reaches three-fourths of the way across the wing, including a fine black longitudinal line in the disc in the posterior portion, its posterior end occupied by a blotch of grey suffusion.

There is an oblique blue-leaden-metallic line from four-fifths of the costa to just beyond this blotch.

The apical area beyond this is brownish, with three whitish costal dots separated by dark fuscous, the last edging a black pre-apical dot.

This article on a moth of the subfamily Apatetrinae is a stub.