Clothes Moths Undressed

By Charlotte Overby | September 2, 2002
From Missouri Conservationist: Sep 2002

Summer is giving way to fall. The sun drops, and for the first time in months, you feel a little shiver of cold. It's refreshing and kind of fun to have goose bumps on your arms again. An extra layer is just what you need, and it feels great to pull on your favorite old wool sweater.

What's this? As you smooth the sweater down over your middle, you see your shirt showing through a small hole. Upon closer inspection, you find a half-dozen, randomly spaced little holes. The moths have done it again—they've chewed holes in your favorite sweater.

Fortunately, of the more than 11,500 species of moths found in North America, only a few are known to take up residence in clothes closets and ruin stored woolens. The three most common fiber villains are in the Tineidae family, one of 65 families of moths. Their common names are the casemaking clothes moth (Tinea pellionella), webbing clothes moth (Tineola bisselliella) and carpet moth (Trichophaga tapetzella). Most people lump them together and refer to them all as clothes moths or miller moths.

They are barely distinguishable from one another and look bland compared to their many colorful cousins. The webbing clothes moth and the casemaking clothes moth are most common. They both are straw-colored with a wingspan that is no more than 1/2-inch long. The casemaking clothes moth has two to three indistinct dark spots on each front wing. If occasionally you see tiny, light tan moths fluttering around the house, they are probably grain moths venturing out of your neglected flour bin or old cereal box.

Although clothes moths are bigger, they are seldom seen because they prefer dark, remote parts of the house, like the top shelf in your closet where you stored your favorite sweater for the summer. They don't fly well and stay concealed, often living in the corners of folded fabric or underneath a hem. They avoid light.

The adults don't eat and, therefore, don't harm your woolens. But they do produce eggs that hatch into fabric-chewing larvae. The food preferences of larvae are unique, even among insects. They are one of the few organisms in the world that can digest keratin, an insoluble, tough structural protein produced by animals. This makes clothes moths perfectly suited for eating keratin-packed natural fibers. They are best known for eating wool, as well as a variety of other fibers such as felt, hair, silk, fur and feathers. Outside, they survive on rotten wood, fungi and dried carcasses.

Many moths have the beauty of butterflies. Who hasn't come across a striking green one or paused to admire an especially fuzzy, long-antennaed moth clinging to a screen door? Moths outnumber butterflies 14 to 1, and like some butterflies, some beneficial species are vanishing as a result of lost habitat and, possibly, due to pesticides and other pollutants. Moths are near the bottom of the food chain and are eaten by countless birds, mammals, fish, frogs, lizards and turtles. Songbirds eat them by the zillions, and grizzly bears pig out on army cutworm moths to fatten up for hibernation.

Moths recycle nutrients, enrich the soil and pollinate many plants. For the last 5,000 years, the almost completely domesticated species, Bombyx mori, or silk moth, has been responsible for spinning most of the world's supply of silk. Computer scientists have imitated the moth's three-dimensional, grid-patterned eye to design optical software.

Many moths, such as the gypsy moth or corn earworm, damage products useful to humans. People spend millions trying to keep them from eating crops and stored goods. The clothes moths are no exception. They rarely bother items that are used regularly, but they infest stored wool sweaters, pants, coats, carpets, down pillows and comforters, mounted animal trophies and upholstered furniture. Sometimes they turn up in air ducts where larvae feed on lint or fur shed by a family pet. They also can originate from an animal carcass or nest that finds its way into your attic, basement or crawl space.

Moths don't live long as adults. They do their damage as larvae.

Like all lepidoptera, clothes moths undergo metamorphosis. Your favorite sweater tucked away on that top, dark shelf was a perfect place for an adult female to lay 100 to 150 tiny eggs in small spaces between your sweater's fibers. In about five days, the eggs hatched and became small, creamy-white caterpillars, no more than 1/16-inch long. They were equipped with well-developed chewing organs and immediately began moving around in your sweater, eating and searching for a protected place to prepare for cocoon-building. The damage was done.

How long they remain in this larval stage depends on conditions and food supply. A fully grown larva can be up to 1/2-inch long, living in a case that gets bigger as the larva grows and eventually transforms into a tough cocoon. Webbing clothes moth larvae attach to one small area of your sweater while they eat it, spinning silken patches or short feeding tunnels for protection. They don't move around much. Casemaking moths enclose themselves in a mobile, protective case as they eat, dragging it with them wherever they please. They eventually settle in a folded corner of fabric or dark, protected cracks high in your closet and make tough cocoons out of the chewed up pieces of your sweater, leaving you with a perforated garment.

Adult moths emerge from the cocoons and have about a week to find a mate. Females emit pheromones to attract males. They mate, and the cycle begins again. The next generation of moths may get into your supply of wool guest blankets or down pillows.

Are you convinced now that your house is infested? Are you ready to doff all natural fiber and switch to polyester, or just go au natural? You don't have to take drastic measures. Clothes moths are fairly easy to thwart.

Keep your woolens clean. Clothes moths are attracted to organic materials, such as body oils, perspiration and saliva, that commonly accumulate on woolens. Dry cleaning or laundering will kill the eggs and larvae.

Don't let stored items go undisturbed for a whole season. Unfold your blankets and sweaters from time to time. Shake them out. Hang your blankets, sweaters and feather pillows outside in the hot sun a couple of times during the summer. Hot, direct sunlight will drive away or kill eggs and larvae.

For long-term storage, keep your woolens in tight-fitting, plastic containers. Remember to clean them before putting them away. Cedar-lined closets or cedar chips placed inside your storage container will curb clothes moths. Cedar masks the males' ability to smell female pheremones, but it doesn't kill eggs or larvae. Neither do common household quantities of mothballs, although they do pose a health risk to pets or kids who could accidentally ingest them. Mothballs contain the chemical naphthalene, which is toxic. Mothballs also have a strong, lingering odor.

Try concocting an old-time moth repellant. In the 1800s, members of the Sturbridge Village farm community in Sturbridge, Mass. used a mixture of dried plants to ward away clothes moths. They placed dried geranium, lavender and tansy, along with pine needles and cedar chips, into small cloth bags and tucked the bags into their folded woolens.

If on that first, chilly fall evening, you discover moths have nestled into your sweater closet, get ready to clean. Empty your storage space and wipe it clean with a wet sponge. Wash your woolens by hand or take them to the cleaners. Give priority to the ones that aren't yet damaged. They are probably harboring eggs that have yet to hatch into larvae. You can also place sweaters and smaller items into a freezer to kill the eggs, or hang them outside for the first frost of the year. Repairing moth-chewed woolens can be tricky. Unlike a snag or little tear that can be stitched closed, moths literally devour part of the material. There's usually nothing to pull back together or rejoin. Try repairing knitted sweaters by turning them inside out and closing the hole the best you can with a needle and fine thread. Bulky yarn and knits tend to hide the repair job better than finer ones.

This Issue's Staff

Editor - Tom Cwynar
Managing Editor - Bryan Hendricks
Art Editor - Dickson Stauffer
Designer - Les Fortenberry
Artist - Dave Besenger
Artist - Mark Raithel
Photographer - Jim Rathert
Photographer - Cliff White
Staff Writer - Jim Low
Staff Writer - Joan McKee
Circulation - Bertha Bainer