Wingspan c. 19 mm.
One of the more distinctive of the Coleophoridae, and one of the larger species, C. lixella has a rather recurved forewing apex and dusky-outlined whitish streaks against a yellow ground colour.
The larva initially feeds on the seeds of thyme (Thymus), feeding within a floret and using this as its case. After overwintering, it changes foodplants to grass, and eventually forms an elongated case from two grass blade portions sewn together.
The adult moths fly in July and August, and can be found on the wing in the afternoon as well as after dark.