The carpet moth does not eat your carpet because it is a carpet. It eats it because it is wool, and wool is dead animal, and the moth’s larva has one of the few digestive systems on earth that can break down keratin. Your good Wilton is, to a carpet moth, a prime meal laid flat across the floor.
That is the first thing to get straight, because it explains everything else. A carpet moth infestation is not a hygiene failure and it is not bad luck. It is a wool problem, a warmth problem, and a stillness problem, and London flats supply all three better than almost anywhere the moth could hope to end up.
I pull up furniture in period conversions across the city and find the same thing under it – a bald grey patch, a scatter of what looks like grains of rice, and a customer who hoovered the open floor religiously for years while the moths ate the two square feet they never once moved the wardrobe off.
Why do London flats suit carpet moths so well?
Because we built the perfect moth habitat and then turned the heating on.
Start with the housing stock. Huge parts of the city are Victorian and Edwardian houses chopped into flats, and those came with wool carpet, wool underlay in the older ones, and skirting-to-skirting fitting that runs under every heavy piece of furniture in the place. Then add central heating, which the moth loves, because warmth speeds its breeding from one or two generations a year to three or four. A cold Victorian parlour got a hard frost through the floorboards every winter that knocked the population back. A centrally heated flat never drops below fifteen degrees, and the moth breeds all year round without a pause.
The last ingredient is stillness. Carpet moth larvae hate light and hate disturbance – they want dark, undisturbed, undisturbed for months. The moth asks for very little: a dark edge, a warm room, and a floor nobody moves the sofa off. A fitted flat with heavy furniture and a busy tenant who vacuums the middle and never the perimeter is a five-star booking.
The undisturbed edge is the whole battleground
Ninety per cent of the damage I see runs in a band around the room’s perimeter and under the largest furniture. The open middle of the floor, where feet fall and the vacuum reaches, is nearly always fine. Larvae will not feed where they get trodden on and hoovered up, so they retreat to the skirting line, the dark strip under the bed, the back corner of the fitted wardrobe. That band is where the eggs go, where the larvae feed, and where any treatment that ignores it will fail. A cleaner who does the open floor and calls it done has cleaned the one part of the room the moth never touched.
What are the larvae eating down there?
Keratin, and you are shedding it onto the carpet every hour you are home.
The larva is the destructive stage – the adult moth has no working mouthparts to speak of and does not feed on wool at all, it only flies about and lays eggs. It is the small cream caterpillar, often dragging a little tube of silk and carpet fibre behind it, that does the eating. What it wants is keratin: wool, obviously, but also human hair, pet hair, feathers from a duvet, and the flakes of skin every person sheds constantly. A perfectly clean wool carpet is edible to a larva. A wool carpet seasoned with months of shed skin, hair, and the grease that comes off a sleeping cat is a banquet.
This is why the dirt matters even though the moth would eat wool clean. The soil is not the food – the wool is the food – but the soil makes the wool more nourishing and more attractive, and a soiled carpet supports a bigger, faster-breeding population than a clean one of the same fibre.
The synthetic carpet nobody wants to hear about
Here is the opinion, and period-flat owners tend to bristle at it: if you have had carpet moths once in a wool-fitted London flat, the honest fix is to stop buying them wool. A polypropylene or polyester carpet contains no keratin, and a carpet moth larva placed on it will starve. It cannot digest a synthetic fibre any more than you can digest sand. People spend hundreds on treatments and traps to protect a wool carpet the moth comes back to, when a synthetic replacement removes the food source permanently and ends the argument. Wool is beautiful and it is also lunch.
How do I tell it is moths and not carpet beetle or wear?
The evidence is specific once you know where to kneel.
Moth larvae leave silken cases – little rice-grain tubes of spun fibre, sometimes stuck to the carpet, sometimes to the skirting just above it. You will see fine webbing in the worst patches, thinning wool that pulls away in a tuft with no resistance, and the larvae themselves if you part the pile in a bad corner. Adult moths are small, buff-gold, and they run and flutter rather than fly strongly toward light the way a clothes moth in the wardrobe might. Carpet beetle damage looks similar but the beetle leaves shed bristly larval skins instead of silk cases, and plain wear leaves crushed, matted fibre rather than fibre eaten down to the backing in a clean bald patch.
The bald patch tells you how long you have had them
A fresh infestation thins the pile. An established one takes it down to the backing in a defined patch with a sharp edge, and by the time you can see the woven backing through a hole the size of a saucer, that colony has been feeding undisturbed for the better part of a year. I found one behind a chest of drawers off Munster Road in Fulham that had eaten a patch the shape of Italy clean through to the gripper rod, and the tenant had lived over it for two winters without once shifting the drawers.
Can cleaning alone get rid of them?
No, and anyone who tells you a single clean will clear an infestation is booking themselves a return visit at your expense.
Here is what a professional hot-water clean does do. It physically removes larvae, eggs, and cases from the fibre by force of water and vacuum. It strips out the shed skin, hair, and soil that feed the colony, which starves down whatever survives. Hot extraction at genuine temperature kills a large share of the larvae and eggs it reaches. All of that is real, and a good clean is a heavy blow to a moth population.
What it will not do is reach the eggs deep in the underlay, the larvae inside the skirting gap, or the colony under the wardrobe you told me not to move. The moth asks for very little, and a protected seam gives it all of it. Moth eggs are laid in the most sheltered spots precisely because that is where they survive. A clean knocks the population down hard, but a handful of eggs in a sheltered seam will repopulate the whole room in six weeks, and then the customer decides cleaning “did not work” when in fact it did exactly what cleaning does and no more.
Heat is the part that kills them
The reason hot-water extraction beats a cold vacuum is temperature. Moth eggs and larvae die at sustained heat above about fifty degrees, which is why proper hot extraction and steam do real killing where a domestic hoover only relocates the problem. On upholstery and rugs a heat treatment, or a spell in a large freezer at minus eighteen for a fortnight, finishes eggs a wash cannot reach. Cold does not clean the carpet, but paired with a proper clean it kills the survivors the water missed, and the two together get you closer to zero than either does alone.
What clears an infestation for good?
A campaign, not a visit. You attack it on every stage of the life cycle at once and then you keep checking.
The sequence that works: move every piece of furniture and treat the whole floor including the perimeter and the underlay edges, hot-clean to remove and kill what is reachable, apply a residual insecticide licensed for the job into the skirting line and under fitted furniture where the clean cannot fully penetrate, and hang pheromone traps to catch the flying adults and show you whether the numbers are falling. Then you do it again in four to six weeks, because that is one moth generation, and the traps tell you whether the second round is finding anyone.
The follow-up nobody wants to pay for
The second visit is the one that gets skipped, and it is the one that decides the outcome. A single heavy treatment feels decisive – the flat looks clear, the traps go quiet for a fortnight, and the customer assumes it is over. Then the eggs that rode out the first round in the underlay hatch on schedule, and by week six there is fresh webbing along the same skirting line. If you treat once and the traps refill, you have not lost, you have reached the point where most people stop and the moth does not. The colonies I clear for good are always the ones where I came back a second time and, often, a third, catching each new hatch before it could breed. It is unglamorous, it is a nuisance to book, and it is the difference between a treatment and a fix.
Prevention afterwards is dull and it works. Move the furniture and vacuum the edges every few weeks so no corner stays undisturbed long enough to host a colony. Keep the wool clean, because a soiled carpet feeds a bigger population. And if the flat has beaten you twice already, look hard at that synthetic carpet, whatever the wool sellers say.
The tenant off Munster Road went synthetic in the end. I have not been called back.





