Carpet beetles: the adult is harmless, the larva is the one eating your jumper
The beetle on the windowsill eats pollen and is usually on its way out. The damage is done by a hairy larva you have probably not found yet, and it is coming from somewhere with protein in it.
By The Pest GuyLast updated
The short answer
If you have seen a small round beetle indoors, the animal in front of you is not the problem.
Adult carpet beetles feed on pollen. They fly well in warm weather and turn up on window sills, which is where nearly everybody meets one. That beetle is not eating your carpet.
The damage is done by the larva, and the larva is the thing you have not seen. It is short, fat and hairy, it hides in crevices and folds, and it eats keratin: wool, silk, fur, feathers and skins. It can take one or two years to finish growing.
So there are two questions worth your time, and neither is which spray to buy first. Where are the larvae, and what are they living on? The answer to the second is very often somewhere nobody looks, and that is what this page is mostly about.
There are three of them in British homes, not one
Almost every page on this subject writes about a single animal called the carpet beetle. The Natural History Museum separates three.
The varied carpet beetle is the one most people mean and the one with the longest history here. The two-spot is native too and commoner in the south. The brown carpet beetle arrived in the 1970s.
The practical use of splitting them is size. If what you are holding is 5mm and plain reddish-brown, it is not a varied carpet beetle, and the larva you are looking for is nearly twice the size you were expecting.
| Species | Adult size | Markings | Larva |
|---|---|---|---|
| Varied carpet beetle (Anthrenus verbasci) | 1.5-3.5mm (English Heritage gives 2-3mm) | Round, mottled white, orange and black patches; grey and gold scales, clubbed antennae | 4-4.5mm, hairy. The classic "woolly bear" |
| Two-spot carpet beetle (Attagenus pellio) | 4.5-6mm | Darker, with two white spots on the wing cases | Up to 6.5mm when fully grown, torpedo-shaped |
| Brown carpet beetle (Attagenus smirnovi) | 2-5mm long, 2-2.5mm wide | Reddish-brown, no patterning | Up to 8mm long |
Natural History Museum, "Carpet beetles identification guide" (sizes and markings); English Heritage / Collections Trust Pest Fact sheet No 1, "Varied carpet beetle" (adult size range, larval description). Both read 2026-09-17.
Two honest limits on that table. The sources disagree slightly on the varied carpet beetle: English Heritage measures the adult at 2 to 3mm, the museum at 1.5 to 3.5mm. Both are right, it is a small and variable beetle, and I would rather print the spread than pick one and pretend to a precision nobody has.
The second limit matters more. A table narrows a shortlist. It does not tell you what is in your house, and I cannot tell you that either, from a description or anything else. If the answer decides whether you throw out a rug, get it looked at by someone in front of it.
What they actually eat, and the one sign that comes first
The larvae are described in the museum fact sheet as voracious feeders that "rapidly make neat holes in woollen textiles, animal specimens, fur and feathers". They will also graze the animal glue in book bindings and picture frames, which surprises people.
What they largely leave alone is clean cotton. The fact sheet is careful about it: cotton "is not normally attacked", although a larva may bore through it on the way out of a feather cushion. So a hole in a cotton sheet over a feather pillow is not the contradiction it looks like.
The first sign is usually not the larva and not the hole. As they grow they shed, and they leave "empty hairy cast skins, or husks". Those husks sit around long after the animal has moved on, and they are what most people find first without knowing what they are looking at. Alongside them you get frass, the gritty pellets of excreta, under or near whatever is being eaten.
That gives you the one distinction worth carrying around, and it is the one that decides what you are dealing with. Beetle damage is clean holes plus powdery frass and no webbing. Webbing in the material means you have the other problem, and the moths page covers that comparison properly, including which life stage the shop shelf is aimed at.
Where they are coming from, which is the half nobody prints
Treat the carpet, leave the reservoir, and you get a second season of it. The fact sheet is specific about where the larvae live.
| Where | What the guidance says |
|---|---|
| Birds' nests, wasp nests and animal burrows | Named by English Heritage as natural situations where the larvae are found. An old nest in a loft or under eaves is a keratin larder |
| Dead insects | "They will feed on dead insects, especially flies". A window-sill or loft graveyard is a food supply |
| Crevices and folds where dirt accumulates | Under and behind furniture, carpet edges, the folds of stored textiles. "Often in dark and hidden places" |
| Carpets, upholstery and clothing | Where most people first notice the damage, which is not the same as where it started |
Read the first row again, because it reframes the whole thing. Birds' nests, wasp nests and animal burrows are named as natural situations for these larvae. An old nest in a loft or packed under the eaves is a larder of feathers and dead insects, sitting directly above the rooms where you are finding beetles.
Stop before you touch anything up there. Wild birds and their active nests are protected, and so are bats and their roosts. An old finished nest and an occupied one are not the same thing in law, and telling them apart is not something to do on a hunch from the top of a ladder. If there is any chance a nest is in use, or that there are bats in the roof, get advice on what applies before you go near it. This is the part of the job where being wrong is not a wasted afternoon.
The second row is the other one people miss. Larvae "will feed on dead insects, especially flies". If you have a windowsill or a loft with a graveyard of flies that came in and died, you have been running a feeding station. The same goes for an old wasp nest left in a loft, which is full of dead wasps and nest material and will never be used again by wasps.
Hoovering a dead-fly collection off a sill costs nothing and removes a food supply. That is an unglamorous sentence and it is worth more than most of what is sold against this animal.
The one aimed at the stage that eats
Same point as on the moths page, for the same reason. The adult beetle feeds on pollen and is mostly trying to get back outside, so anything aimed at the insect you can see is aimed at the wrong half of the animal. A residual product works on the larvae in the carpet edges and crevices. It does nothing whatsoever about a nest in the loft, and if that is where yours are coming from, this is the part you do after you have dealt with that.
What I’d use
Residual insect spray, 600ml
Zero In Ultra Power Insect Pest Killer (600ml)
A prallethrin and cyphenothrin contact spray, claiming residual control of emerging eggs and larvae for up to 12 weeks.
It is aimed at the life stage that is actually doing the damage. The adult clothes moth has no working mouthparts and eats nothing, so anything sold on killing the insect you can see is treating the wrong stage. A residual claim against emerging eggs and larvae is the only part of this category pointed at the larvae, which are what is in the fabric.
- Size
- 600ml
- Actives
- Prallethrin and cyphenothrin
- Residual claim
- Up to 12 weeks on emerging eggs and larvae
- Listed for
- Fleas, bed bugs, clothes moths and other household insects
- Use
- Indoor only
Watch out for
- The 12 weeks is the manufacturer claim, not an independent test.
- Indoor only, and not suitable for use around pets.
- Very toxic to aquatic life, with long lasting effects.
- Danger: extremely flammable aerosol, and it may burst if heated.
That link earns me nothing. It is not an affiliate link, no brand pays for a mention here, and I get the same whether you buy this or ignore it. It is on the page because it is what the job takes.
No brand pays for a mention here, and nothing on this page earns me a commission. The card above links out to a shop, and I get the same whether you buy or ignore it. The link is there because finding the thing is the boring half of acting on advice, which is also why the watch-outs sit on the same card as the reasons to buy.
The bite question, answered straight
After the removal terms, this is the single most-asked thing about carpet beetles, and the answer is no. Neither the Natural History Museum guide nor the museum pest fact sheet records a bite. What both describe is damage to materials: wool, silk, fur, feathers, skins, book glue. Nothing about people.
What people do report is a rash, and it is worth being precise about why, because "carpet beetle bites" is the wrong name for it and the wrong name sends you after the wrong thing. The larvae are covered in hairs. A reaction to those hairs is a contact reaction, not a bite, and it explains the thing that puzzles people most: one person in a household reacts and nobody else does. A biting insect does not usually work like that.
I will not go further than that, and here is the honest reason. What is actually on your skin is a medical question, and a pest website is a bad place to settle one. If a rash is spreading, weeping, infected-looking or simply will not go, see a pharmacist or your GP. If it turns out to be bites after all, that changes what you are looking for, and bites in a house with no animal in it have their own explanation that has nothing to do with beetles.
What actually ends it
In order, and the order is the point. Find the reservoir first. Lofts, eaves, under the floor, behind and under heavy furniture that never moves, the backs of wardrobes, stored wool. Anything with feathers, fur or dead insects in it is a candidate.
Then deal with the food supply you can reach safely. Dead insects off sills and out of light fittings. Stored wool and fur gone through and either used, washed or sealed. Carpet edges and the strips under furniture hoovered properly, because that is where the larvae sit and where the dirt they like accumulates.
Then, and only then, is a residual product worth anything, because by that point it is finishing a job rather than doing one. A larva that takes a year or two to grow is not a problem you solve on a Saturday, and anyone telling you a single visit ends it is selling the visit.
One more thing, and it is the one that costs somebody else money rather than you. If this is a rented home and the reservoir turns out to be a nest in a roof void or a gap in the fabric of the building, that is a repair question before it is a pest question, and the bill may well not be yours. Worth settling before you start buying things.
About this resource
The species, sizes, lifecycle, damage and the list of where larvae are found all come from two published sources: the English Heritage and Collections Trust museum pest fact sheet for the varied carpet beetle, and the Natural History Museum's carpet beetle identification guide. Museums have been fighting this beetle in collections for a very long time, and their guidance is more specific than anything written to sell a treatment.
The honest limits. I have not measured a beetle or tested a product, and nothing here is a test result. Where the two sources give different sizes for the same animal I have printed both rather than split the difference. I cannot tell you which species is in your house or what has marked your skin, and the page is built so that nothing on it depends on my being able to. The legal position on nests and roosts is pointed at here, not summarised: check what applies before touching anything in a loft.
Common questions
Do carpet beetles bite?
No. Neither the Natural History Museum nor the museum pest fact sheets list any bite among the damage they do, and what those sources describe is damage to materials rather than to people. What does get reported is a skin reaction to the larvae, which are covered in hairs, and that is not the same thing as being bitten. If you have an unexplained rash that is spreading or will not settle, that is a question for a pharmacist or your GP rather than for a pest page.
What does a carpet beetle look like?
The varied carpet beetle is the one most people mean: a small round beetle about 1.5 to 3.5mm long, mottled with white, orange and black patches, with clubbed antennae. The Natural History Museum also records two others in British homes, the two-spot at 4.5 to 6mm with two white spots on the wing cases, and the brown carpet beetle at 2 to 5mm and plain reddish-brown. The larvae look completely different: short, fat and visibly hairy, which is why they are called woolly bears.
Can carpet beetles fly?
Yes. The English Heritage fact sheet says adults "fly well in warm weather and may frequently be found on window sills". That is where most people meet one, and it is usually an adult trying to get out rather than one arriving.
Where do carpet beetles come from?
Two routes. Adults come in from outside, where they feed on pollen and mate on flowers such as hogweed in late spring and early summer, and the museum guidance notes they can also arrive on dried fruit and nuts. The larvae come from somewhere with protein in it. The fact sheet names birds' nests, wasp nests and animal burrows, and says they will feed on dead insects, especially flies.
Are carpet beetles dangerous or harmful?
Not to the building and not to you in the way people fear. They do not damage structure, they are not recorded as biting, and the published damage is to wool, silk, fur, feathers and skins. The cost is to your things, and it can be real: the larvae make neat holes in wool and will graze animal glue in book bindings and picture frames.
Am I dirty if I have carpet beetles?
No, and this is the question the harvest turned up most often, asked five or six different ways. Carpet beetles are not a hygiene failure. They want keratin, which is wool, fur and feathers, and they want undisturbed dark places. A clean house full of wool rugs is better habitat than a messy one furnished in polyester. The one honest link to cleaning is that larvae sit in crevices and folds where dirt gathers, so the places you never hoover are the places to look.
Does one carpet beetle mean an infestation?
No. A single adult on a windowsill in early summer is the commonest sighting there is, and on its own it means one beetle came in. What would change that is evidence of larvae: cast skins, which are hollow and hairy, and gritty frass under or near wool. Cast skins are usually the first real sign, because the larva itself hides.
What time of year are carpet beetles most active?
Adults emerge in the warmer months and are found outdoors in late spring and early summer, which is when you see them on windowsills. The larvae are the part with no season: the museum guidance notes that in centrally heated buildings both adults and larvae turn up all year round.
What gets mistaken for carpet beetles?
Clothes moths, mainly, and the damage tells them apart better than the insect does. Carpet beetle larvae leave small, clean holes with no webbing, plus powdery droppings. Clothes moth larvae leave silk webbing in the material. If there is webbing, you are looking at the other problem.