Wingspan c. 14mm.
The scientific name of this species is derived from the whitish streak along the costa, or forewing edge.
Flying by day, but also sometimes coming to light at night, the adults are on the wing in June and July, and the species is fairly common throughout the British Isles.
The larva feeds on gorse (Ulex europaeus). At first, it feeds on green seeds inside a seedpod. From July to November, it lives in a detached sepal rolled into a case, which it attaches to the side of a seedpod and bores in to feed on the seeds. From November to April, it diapauses full-fed in a silk case in a dead flower. In April it pupates in the overwintering case.