Wingspan c. 7mm.
A tiny nondescript species not often seen as an adult, although fairly widespread in England. It is less common elsewhere in Britain.
The larva feeds on yarrow (Achillea millefolium), in a leaf mine to begin with, then later feeding externally on the leaves, shrivelling and blanching or browning them. The larva can be found in April and May and again in July. Twice during its growth, it spins a white cocoonet in which it moults its skin. The cocoonet is constructed on the upper surface of a leaf, where it is easily detected. If held up to the light, the larva, or its cast skin retaining the larval shape, can be seen.
Like other Bucculatriginae, the pupa, on the foodplant or adjacent plants, is in a distinctive whitish ribbed cocoon. The adults fly in two generations; May and June, then July to August.