Wingspan 7-12 mm.
A fairly common species throughout England and Wales, extending into southern Scotland, flying in June and July.
The female moth is slightly smaller than the male, and both can be found resting on tree trunks during the flight period.
The larva lives in a case, and attaches itself to a tree-trunk, fence or other lichen-covered surface.
Larva: (description I.F. Smith)
Food: Aug-May. Algae and lichens on tree trunks, fences etc. Diet may influence body colour. Specimens found on the lichen, Lepraria incana, on street trees in Manchester had yellow bodies and ochre gut contents. Those on other encrustations on more rural trees, on the same late March date, had greyish white bodies and blackish gut contents.
Pupa in larval case May-June.
Length: 6 mm larvae described
Case: 6mm. Approximately triangular in cross section, tapering at ends. Ventral surface often slightly 'pot bellied'. White silk coated with sand, dried frass and, especially on dorsal faces, granules of alga and lichen.
Pupal exuviae 4 mm, extruded from end.
Head: Pitchy black. Fine colourless epicranial and adfrontal cleavage lines. Mouthparts dark brown.
Prothorax (T1): As abdomen; yellowish or greyish white. Pitchy brown subventral sclerite and ventral sclerite.
Prothoracic shield pitchy brown, divided by pale median line
Mesothorax (T2): As abdomen; yellowish or greyish white. Large dark brown or pitchy dorsal sclerite, divided by paler median line. Two lateral, one subventral and one ventral pitchy sclerites.
Metathorax (T3): As abdomen; yellowish or greyish white. One dorsolateral , two lateral, a subventral and a ventral, pitchy sclerites.
Thoracic legs: Pitchy black. Base concolorous with body, with a dark sclerite.
Body: Abdomen much fatter than thorax. Yellowish or greyish white. Translucent, with ochre or blackish viscera partly visible.
Anal plate: Dark brown or pitchy black.
Ventral Prolegs: Vestigial; small whitish planta, distinct pitchy crochets.