Plectophila placocosma is a moth in the family Xyloryctidae. It was described by Oswald Bertram Lower in 1893. It is found in Australia,[1] where it has been recorded from New South Wales.
The wingspan is about 14 mm. The forewings are white, slightly ochreous tinged and with a broad dark fuscous fascia suffused on the lower half, the anterior edge curved from one-sixth of the costa to one-sixth the inner margin. There is a large irregular fuscous patch on the costa beyond the middle, reaching more than half across the wing, the anterior edge preceded by a blackish discal spot. There is a large fuscous patch on the hind margin from the apex to the anal angle and a fuscous hindmarginal line, separated from the preceding patch by a streak of the ground colour. The hindwings are yellowish, with a broad fuscous suffusion occupying the posterior two-thirds of the wing.[2]