Ethirostoma semiacma is a moth in the family Gelechiidae. It was described by Edward Meyrick in 1914. It is found in Guyana.[1]
The wingspan is 8–10 mm. The forewings are purplish fuscous, more or less suffusedly irrorated (sprinkled) with white and with a dark fuscous erect mark from the base of the dorsum and an irregular dark fuscous spot beneath the costa at one-fifth. There is a dark fuscous transverse streak from the dorsum at one-fourth, reaching halfway across the wing, posteriorly edged with white and there is a thick black streak along the costa from before the middle to near the apex, cut by two very oblique white strigulae from beyond the middle and at two-thirds. The stigmata are dark fuscous, the plical obliquely before the first discal, followed by a raised white spot, the first discal indistinct, the second enlarged into an irregular spot followed by a whitish tuft and there is an irregular elongate ochreous-white apical blotch, from the anterior extremity of which a faint dentate whitish line runs to the tornus. A leaden-grey spot adjoins an apical blotch beneath. The hindwings are grey in males and dark grey in females, thinly scaled towards the base.[2]