What Does Woodworm Look Like? The Complete Visual Guide
See what woodworm looks like: exit holes, bore dust, tunnels, larvae and beetles. Learn to tell an active infestation from old damage and when to call a pro.
Woodworm looks different at each stage. The grub is hidden, the damage is small, and the beetle is easy to miss. Knowing what each stage looks like helps you spot a problem early.
This guide describes the holes, dust, larvae and beetles you may find. It also shows how to tell a live problem from an old one.
The exit holes
Exit holes are the most common sign. They are round, clean and small, usually 1 to 2mm wide for the common furniture beetle. Think of the tip of a pin or a sharp pencil.
Fresh holes have pale, sharp edges. Old holes look darker and duller, because dust and age have dulled the wood. Bigger holes suggest another species, so check the species guide if yours are wider than 2mm.
The bore dust
Bore dust, or frass, is a fine, gritty powder. It is cream or biscuit-coloured and feels faintly sandy. Under a magnifier you can see tiny lemon-shaped pellets.
Dust gathers under holes on floors, skirting boards and windowsills. If it returns after you clean it away, the beetle is probably active. If it never returns, the damage is probably old.
The larvae
The larva is the “worm”. It is creamy white, curved like the letter C and about the size of a grain of rice when grown. You almost never see it, because it lives inside the wood. Our guide to woodworm larvae shows what they look like and how big they get.
The tunnels
Where wood has split or been cut, you may see tunnels packed with dust. They run along the grain and make the timber look honeycombed. Heavy tunnelling means the beetle has worked there for years.
The adult beetle
Adult furniture beetles are small and brown, about 3 to 5mm long. They look hunched from above, and they have faint rows of pits on their wing cases. You may find them on windowsills in summer, since they fly toward light. The post on the woodworm beetle covers the other species.
Weak timber
Damaged wood feels light and crumbles at the edges. A screwdriver sinks in too easily. Floors may bounce, and rafters may sag. Weak timber is a sign to book a survey, because the structure may be at risk.
Is it active?
Use three checks:
- Fresh dust that comes back after cleaning
- Pale, sharp-edged holes
- Beetles in late spring or summer
If you see none of these, the holes are probably old. Read active versus historic woodworm for the full test.
What to do next
If the signs look live, read how to treat woodworm for your options. If you are unsure, request a survey. A surveyor can name the beetle and say whether treatment is needed.
Where you live matters, because older streets hold more old timber. See our local guides for woodworm treatment in Leeds and woodworm treatment in Edinburgh.
To go deeper, read about the common furniture beetle and the powderpost beetle, because the right method depends on the beetle.