Wingspan 10 -15 mm.
C. asteris can be locally common on saltings where its foodplant, Aster tripolium, grows in England and North Wales. It flies from June to September.
Its forewing is brownish buff with white along the veins, and there is a scatter of blackish scales on both white and buff areas. The leading edge of the forewing is white from the head to just over half its length, the remainder being buff. The whitish antenna has black dots along its underside. There are several similar species so, unless reared from Aster tripolium, examination of the genitalia, aided by MBGBI-3, is advised. C. obscenella, which also feeds on Aster tripolium, has white along the whole length of the leading edge of the forewing.
The cased larva feeds on the seeds in September and October, when it is full-grown. It overwinters in debris until pupation in June. The 6 mm brown silk case is cigar shape with slight wrinkling. The case of C. obscenella is covered in seed hairs in autumn, but they may be worn off by spring, when the case might be confused with that of C. asteris.