The testaceous white-back (Coleophora albicosta) is a moth of the Coleophoridae family. It is found in most of western Europe. The wingspan is about 14 mm. Adults are on wing from June to July. They fly by day, but also sometimes come to light at night. The larvae feed on Ulex europaeus. First it feeds on green seeds inside a seedpod. Then 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. Finally, it diapauses full-fed in a silk case in a dead flower and pupates in the overwintering case.