Brown house moth larvae are small, white, worm-like caterpillars that feed on animal-based fibers, dried food, and organic debris inside homes. At roughly 10 mm long when fully grown, they’re easy to overlook, but the damage they leave behind on woolens, carpets, and upholstered furniture is hard to miss. If you’ve spotted tiny translucent grubs or unexplained holes in stored clothing, these larvae are a likely culprit.
What They Look Like
A fully grown brown house moth larva measures about 10 mm, roughly the width of a fingernail. The body is translucent white, so transparent in places that you can see reddish internal organs through the skin, especially in the front two-thirds of the body. The head capsule is reddish brown with darker mouthparts along the front edge. Each larva has small, shiny raised spots (called pinacula) running along its back and sides, though these are the same pale color as the body and hard to see without magnification.
The legs are translucent white, and the tiny hook-like grippers on the prolegs (the fleshy leg stumps on the abdomen) are tinted a burnt ochre color. Overall, the larva looks like a small, pale, slightly glossy worm with a distinctly darker head. If you find one on a dark wool sweater or inside a wardrobe, the contrast makes it easier to spot than you’d expect.
What the Larvae Eat
Brown house moth larvae are generalist feeders, which makes them more destructive than some of their relatives. They digest keratin, the protein found in wool, fur, silk, feathers, felt, and leather. In the wild, they feed on bird nesting material and animal carcasses. Inside your home, they target the same proteins in a long list of items: sweaters, scarves, coats, blankets, rugs, down pillows and comforters, upholstered furniture, stuffed toys, decorative items, and taxidermy mounts.
Cotton and synthetic fabrics like polyester and rayon are rarely attacked on their own. But if those fabrics are blended with wool, or if they’re heavily soiled with food stains or body oils, larvae will feed on them too. The oils and skin cells you leave on clothing essentially season the fabric, making otherwise unappealing materials a viable food source.
Larvae also thrive in places you might not think to check. Vents and ducts can accumulate lint, shed pet hair, and other bits of organic debris that sustain a colony. Infestations sometimes originate from bird nests in attics or chimneys, or from animal carcasses trapped in wall cavities. These hidden food sources can keep a population going long after you’ve cleaned out your closets.
Signs of Larval Damage
The most obvious sign is irregular holes in wool or silk garments, particularly in items that have been stored for weeks or months without being disturbed. Unlike carpet beetle damage, which tends to follow the surface of a fabric, moth larvae often eat through the material, leaving holes with slightly ragged edges. You may also notice fine silk webbing or small silk tubes on the surface of infested items. The larvae spin silk as they move and feed, and this webbing sometimes traps tiny sand-grain-sized droppings (frass) that match the color of whatever fabric the larvae have been eating.
Check the undersides of rugs, the backs and bottoms of upholstered chairs, and the seams of stored blankets. Larvae prefer dark, undisturbed areas, so damage often starts in spots you don’t regularly see. Finding shed larval skins, which look like empty translucent husks, is another strong indicator that a population has been developing over time.
Where Infestations Start
Brown house moths are widespread in temperate climates and fly indoors through open windows and doors, especially in warmer months. But many infestations don’t start with a moth flying in. Secondhand rugs, vintage clothing, antique furniture, and inherited textiles can all carry eggs or larvae into your home. Bird nests under eaves or in chimneys are another common entry point. Once the birds leave, the larvae in the nest can migrate indoors through small gaps.
Indoors, female moths seek out dark, quiet locations with a reliable food source. Walk-in closets, attic storage boxes, under-bed containers, and the insides of upholstered furniture all fit the bill. Rooms that stay warm year-round allow larvae to develop faster, which is why centrally heated homes tend to have worse infestations than drafty older buildings.
Killing Larvae With Heat or Cold
Temperature is the most reliable non-chemical way to kill brown house moth larvae at every life stage, including eggs. Washing infested clothing or blankets in water at 120°F (49°C) or above for 20 to 30 minutes kills larvae and eggs. For items that can handle it, a hot dryer cycle after washing adds an extra layer of certainty.
Items that can’t be washed, like a wool coat or decorative textile, can be heated in an oven at temperatures above 120°F for at least 30 minutes. Alternatively, sealing the item in a plastic bag and placing it in a freezer below 18°F (-8°C) for several days works as well. The key with freezing is sustained cold. A few hours isn’t enough. Leave items in the freezer for at least 72 hours to ensure eggs are destroyed too.
Insecticide Options
One important quirk of brown house moths: no species-specific pheromone trap exists for them. Pheromone traps designed for webbing clothes moths or Indian meal moths will not attract brown house moths, so purchasing generic “moth traps” is likely a waste of money for this species.
Chemical control typically involves a surface spray applied to areas where larvae are active, such as the base of wardrobes, carpet edges, and the underside of furniture. Insecticidal powders, including diatomaceous earth, work well for long-term prevention in low-traffic areas like wall voids, loft spaces, and behind heavy furniture. These powders damage the larvae’s outer coating, causing them to dehydrate. Insecticidal smoke generators or foggers can reduce the adult moth population in enclosed rooms, cutting down on future egg-laying.
The most effective approach combines methods. Start by finding and removing the source of the infestation, whether that’s a neglected wool rug, a forgotten box of blankets, or a bird nest in the attic. Then treat the surrounding area with a residual surface spray to catch any larvae or adults you missed, and use powders in hidden voids for ongoing protection.
Preventing Reinfestation
Clean before you store. Laundering or dry-cleaning wool and silk garments before putting them away removes the body oils and food residues that attract larvae. Store clean items in airtight containers or vacuum-sealed bags. Zippered garment bags work for coats and suits, but only if there are no gaps at the seams.
Vacuum regularly in the places larvae prefer: along baseboards, under heavy furniture, inside closets, and around the edges of fitted carpets. Pay special attention to areas where pet hair collects, since fur is a high-protein food source for larvae. If you have bird nests on or in your home, remove them once the birds have fledged and seal the entry points.
Cedar and lavender are often recommended as repellents. They may discourage adult moths from laying eggs in a treated area, but they won’t kill existing larvae and their effectiveness fades as the scent dissipates. Treat them as a supplement to cleaning and proper storage, not a standalone solution.