Deltoplastis horistis is a moth in the Lecithoceridae family. It was described by Meyrick in 1910. It is found in India (Assam). The wingspan is about 21 mm. The forewings are blackish-fuscous with the costal area above a line running from the base of the dorsum to four-fifths of the costa whitish-ochreous, within this, the basal third of the costa is suffused with dark fuscous, the rest of the costal edge ochreous-orange. There is a slender whitish-ochreous streak running from this pale costal area in the middle of the wing to the dorsum near the tornus and there is a slightly irregular white line from the costa near the apex to the tornus. Some cloudy white submarginal dots are found around the apex and termen, and there is a black marginal line. The hindwings are fuscous, towards the ba