Holes in a Wool Sweater Aren't Always "Moths" — Two Different Insects Cause This

Pulling a wool sweater, an old rug, or a stored blanket out of a cupboard and finding irregular holes in it gets blamed on "moths" almost automatically. That's often correct, but a second insect — the carpet beetle — causes very similar damage for a related but distinct reason, and the two aren't interchangeable when it comes to figuring out what actually helps. Both belong to a small group of pests with an unusual, specific diet that sets them apart from almost every other household insect, and both are frequently misidentified as the other simply because the end result — a hole in a favourite sweater — looks so similar either way.

Why wool, silk, and fur specifically

Clothes moth and carpet beetle larvae share a genuinely unusual biological trait: they can digest keratin, the structural protein that makes up wool, silk, fur, feathers, and leather. Most insects, and most other fabric-damaging conditions, can't break keratin down at all, which is exactly why these two are drawn specifically to natural animal-fibre textiles rather than cotton, linen, or synthetic fabrics — a stored cotton bedsheet or a polyester jacket simply isn't a food source for either insect, while a wool coat or a silk scarf very much is. This is also why a mixed-fibre item is more vulnerable at the wool or silk portion specifically, and why an all-synthetic wardrobe is a far lower-risk target for either pest, even if it's kept in exactly the same closet as a vulnerable one.

It's the larvae doing the damage, not the adults

For clothes moths in particular, the adult stage doesn't feed at all — an adult clothes moth exists purely to mate and lay eggs, and all of the actual fabric damage happens during the larval stage that precedes it. This means seeing adult moths fluttering around a closet doesn't mean damage is happening at that exact moment, but it does mean a population exists and has already laid, or will soon lay, eggs somewhere nearby. Carpet beetle adults are a little different — many feed on pollen and nectar outdoors rather than fabric — but it's still the larval stage indoors that causes essentially all of the damage to stored textiles, which is why noticing adults is a useful warning sign rather than a picture of the damage actively in progress.

Telling the two apart from the damage and debris left behind

Clothes moth larvae tend to prefer dark, undisturbed spots and often spin a thin silk feeding tunnel or patch of webbing over the area they're actively feeding on, which can sometimes be spotted before the hole itself is obvious. Carpet beetle larvae look distinctly bristly or hairy under close inspection, don't spin webbing, and tend to leave a more generalized "grazing" pattern across a wider surface area rather than one concentrated hole, along with small shed larval skins scattered nearby as they moult while growing — a detail that's often the clearest giveaway once you know to look for it. Both patterns show up most often in the same kinds of spots: undisturbed drawers, the underside of rugs, along carpet edges tucked under furniture, and stored garments that haven't been moved or aired out in a long while. A magnifying glass or even a phone camera's zoom is often enough to tell webbing from shed skins clearly, which is worth doing before assuming either identification from the hole alone.

Why the damage is usually only discovered months later

Both pests strongly prefer feeding undisturbed, in the dark, for extended stretches of time, which is exactly what a seasonally stored item provides — a wool coat put away for several months of warm weather, or a rug rolled up and left in a store room, offers uninterrupted access with essentially no risk of being disturbed mid-feed. This is a large part of why the damage is so often discovered only when the item comes back out for use — taking woolens out at the start of a cooler season, unrolling a rug after months in storage — rather than at the point the damage actually happened. By the time it's noticed, the feeding that caused it may have finished weeks or months earlier, which makes it easy to mistakenly blame whatever conditions are present at the moment of discovery rather than the actual undisturbed storage period that preceded it.

Why stains and soiling attract them as much as the fibre itself

Both pests are drawn not just to the wool or silk fibre itself but to perspiration, food residue, and other organic soiling left on fabric, which is a large part of why a worn-but-unwashed item stored away tends to attract far more attention than a genuinely clean one. This is exactly the reasoning behind the long-standing advice to always wash or dry-clean wool and silk items before putting them into long-term storage — it isn't just about general tidiness, it measurably reduces how attractive the item is to begin with, independent of anything else done to protect it afterward.

Why cedar and mothballs reduce risk without guaranteeing it

Cedar oil and mothball vapours work as repellents — they can discourage egg-laying in a contained, sealed space where the vapour concentration stays high enough to matter. Their effectiveness drops considerably once a space is well-ventilated or only loosely enclosed, since the vapour simply doesn't build up to a meaningful concentration, and neither approach does anything for a population that's already established inside the stored item itself before it went into storage. Treating these as a modest additional layer of protection within a properly sealed storage container, rather than a stand-alone solution on their own, is a more realistic way to think about what they actually contribute — a cedar block sitting loosely on an open shelf next to a sweater is doing considerably less than the same block inside a sealed container with that sweater.

• Wash or dry-clean wool, silk, and fur items thoroughly before long-term storage — soiling and perspiration residue attract both pests independent of the fibre itself.
• Store vulnerable items in sealed, air-tight containers rather than open shelving, loosely closed boxes, or garment bags with gaps.
• Periodically inspect stored wool and silk items even when sealed, rather than assuming a container guarantees safety indefinitely.
• Vacuum carpets and rugs regularly, paying particular attention to edges tucked under furniture and other undisturbed spots carpet beetle larvae favour.
• Treat cedar or mothball products as a modest supplement inside a properly sealed space, not a substitute for cleaning and proper storage.
• Look for the specific evidence (silk webbing vs. bristly shed larval skins) to identify which of the two you're actually dealing with before assuming a fix will work.

If fabric damage keeps showing up despite reasonable storage habits, spans multiple items rather than a single unlucky sweater, or you're not sure which of the two pests is actually responsible, a proper inspection is the most reliable way to find out before committing to a fix. Sevacorp offers a free inspection before any treatment is scheduled, so you'll know exactly what's driving it — and what it will take to bring it under control — before committing to anything.