Reading the Damage

Sign one

Thinning and Bald Patches, in the Wrong Places

Moth damage does not look like wear. Wear appears where feet go - doorways, the route from the door to the sofa, the bottom of the stairs - and it is gradual and even.

Moth damage appears where feet do not go. Under the sofa, behind the door, along the skirting, under a rug, in the corner of a spare room. It starts as thinning, as though the pile has had a haircut, and progresses to bare backing in patches with soft, irregular edges.

If a carpet is worn in the middle and perfect at the edges, that is use. If it is perfect in the middle and thin at the edges, that is worth investigating.

Sign two

Cases and Webbing

The case-bearing larva drags a silk tube camouflaged with fibre from whatever it is eating, so it matches your floor. Four to ten millimetres, tapered, and easily mistaken for a bit of fluff. They turn up in the pile, at the junction of carpet and skirting, and stuck to the underside of shelves and the tops of skirting boards when the larva climbs to pupate.

The webbing species leaves silk instead: fine, slightly matted patches over the surface of the wool, sometimes with grains caught in it, often in a wardrobe or on the underside of a rug.

Either one is direct evidence of feeding in that spot, which is considerably more useful than a moth at a window.

Sign three

Frass, Which Is the Colour of the Carpet

Frass is larval droppings, and it comes out the same colour as whatever has been eaten. On a beige carpet it is fine beige grit. It collects in the pile under the affected area and along the skirting, and it feels like sand between finger and thumb.

It is easy to dismiss as ordinary grit, so the test is where it is. Sand and grit are tracked in and end up where people walk. Frass is in the places nobody walks, directly under damage.

Sign four

Damage on the Shoulders, and Holes That Are Not Round

In a wardrobe the pattern is distinctive. Damage concentrates on shoulders, collars, cuffs and anywhere that carried body oils, sweat or food - which is why a jumper worn once before being put away is more at risk than a clean one.

The holes are irregular, with a grazed thinning around them rather than a clean edge, and they often come in loose clusters rather than singly. A single clean round hole is more likely a cigarette burn, a snag or a carpet beetle.

The question that matters

Active or Historic?

This is the one that decides whether you need treating at all, and it is the question a survey exists to answer.

Active means live larvae, fresh pale cases, silk that is clean rather than dusty, frass sitting loose on the surface, and adults in season. Historic means bare patches with none of that: old cases that are empty and dusty, no frass, no movement when you part the pile.

Bare patches in a house that has changed hands are very often historic. Somebody else's problem, finished years ago, with the damage left behind. Treating that is money spent on nothing, and we will say so.

The reliable way to check at home: part the pile at the edge of a damaged area in good light and watch for thirty seconds. Larvae move, slowly, and cases shift.

Short answers

Carpet Moth Questions

Going further

Carpet Moth Guides