Opomyzidae

Slender to very slender flies, 2-4.5 mm long, shining to pruinose
yellow, reddish, brown, or blackish. Head more or less rounded with only
one pair of fronto-orbital setae. Wing always with at least an apical
spot, usually with more extensive markings. Larvae develop within the
stems of Gramineae, causing damage termed "dead heart". (Vockeroth 1987, Brunel 1998)