Elachista perniva  Elachista perniva is a moth of the family Elachistidae. It is found in North America in Saskatchewan, Colorado and Wyoming. The length of the forewings is . The costa in the basal fifth of the forewing is grey. The wing is otherwise snow-white. The hindwing varies in colour from light grey to dark brownish grey. The underside of the wings is dark grey. The species name is derived from Latin "per"- and "niveus " (meaning very snowy).