What distinguishes the case-bearing moth from the others is the silken case the grub weaves to protect itself while it is eating your carpet. It can turn around inside to eat at both ends. When it is large enough this case is sealed while the grub pupates and becomes a moth. These cases, which look like a grain of rice, can be hidden behind furniture or in any nook or cranny but, with a large infestation, can appear in hundreds on the walls and ceilings.
Why moths don’t deserve their demon status
When the moth appears it has a wingspan of only 15-17 mm and is pale grey to brown with vague dark spots. It is hardly conspicuous and lives only long enough to mate and lay between 30 and 300 eggs back on the remains of your carpet to start the cycle all over again.
There are lots of ways of attacking this unwelcome visitor. Regular vacuuming is the best preventative measure, but is not enough. The grubs like to live in dark corners so they have to be hunted down. There are a variety of natural remedies, including moth papers to trap the adults. There are also insecticide sprays for reaching under the skirting boards, large bits of furniture or loose rugs. All are supposed to see them off, although repeated treatments might be needed.