They don’t, technically. It’s actually their larvae, or caterpillars, that eat clothes, not the adult moths.
It’s only a relatively small group of moths, the family Tineidae, that have any interest in your clothing. Throughout much of the US, you’ll only find two Tineidae species: the webbing clothes moth (Tineola bisselliella) and the casemaking clothes moth (Tinea pellionella). They’re not attracted to your closet for a meal, because the adults don’t eat, and don’t even have the mouthparts if they wanted to. Rather, your clothing is a good place for them to lay a few hundred eggs.
Once these eggs hatch into larvae, then you’ve got a problem. The babies need plenty of protein to move on to the pupa and adult stages of their life cycle and have adapted to eating keratin, the fibrous proteins found in animal hair and skin. This means wool, fur, feathers, leather and even lint are all on the menu. Larvae have been known to chew through cotton, acrylic, polyester and other plant-based and synthetic fibers, too -- not to eat them, but to clear a path to their preferred foods.
The Mothball Defense
When people have clothing moths, they usually turn to mothballs as their first defense, but it isn’t the best one, cautions the National Pesticide Information Center. Outside of an airtight container, the concentration of mothball fumes isn’t high enough to wipe out the bugs, but can cause headaches for humans.
The best way to deal with an infestation, the experts say, is to dry clean anything made of wool or animal fibers and wash everything else in your washing machine’s hot wash cycle. Then, vacuum the floor, the bottoms and tops of the shelves, and even the ceiling to remove any remaining eggs and hungry larvae.