Case-bearing moth larva (plaster bagworm)

Humid indoor areas, especially walls, ceilings, closets, and corners where lint and spiderwebs accumulate.

Larvae feed on lint, hair, dead insects, and other dry organic debris; they may also consume natural-fiber fabrics.

The caterpillar lives inside a spindle-shaped silken case covered with debris and carries it as it crawls. It pupates within the case, often attached to a wall.

Harmless to people and not a health risk; large numbers can occasionally damage wool, silk, or other natural-fiber items.