It shows up on your bathroom wall. Small, grey-brown, slightly armoured-looking. You have no idea what it is.
The EEIK community identified it immediately when this question came up: it is almost certainly a woodlouse, and you do not need to panic.
What Is a Woodlouse?
A woodlouse — also called a pill bug, roly-poly, potato bug, or isopod — is a small crustacean, not an insect. The one in your apartment is likely 5 to 15mm long, oval-shaped, and segmented. Some species roll into a ball when disturbed.
Despite looking mildly alarming the first time you see one, it is harmless. It does not bite. It does not sting. It does not damage walls, food, furniture, or clothing.
Why Is It in Your Apartment?
Woodlice are moisture-loving creatures. They live in damp, dark places and feed on decaying organic matter — old wood, wet cardboard, mold, decomposing leaves, and similar material.
In Korean apartments, the most common entry points and hiding places include:
- Bathroom and kitchen drains
- Cracks around pipes or in baseboards
- Gaps near windows, balcony doors, or floor drains
- Damp corners with poor ventilation
If your building is older, has a semi-basement component, or gets significant humidity in summer, occasional woodlouse sightings are fairly common. Seeing one does not mean your apartment is dirty or that there is a serious problem.
What to Do
The 58-member EEIK thread converged on a short practical checklist:
Clean your drains. Bathroom and kitchen drains are the most reported entry point. A drain brush, some cleaning solution, and a drain cover go a long way.
Reduce humidity. Air the apartment regularly, especially in bathrooms. If you use a clothes horse indoors, make sure the space ventilates. A small dehumidifier can help in summer.
Check for damp or decaying material. Wet cardboard boxes, old wood, damp corners behind furniture, or condensation-heavy walls can attract and sustain them. Remove or dry out anything that fits this description.
Seal gaps. Small gaps around pipes, under doors, or in baseboards can be sealed with caulk or weatherstripping. This is worth doing anyway for insulation.
Scoop and release rather than kill. Several community members suggested this — they are harmless and play a small role in breaking down organic matter. A piece of card and a cup is all you need.
When to Be More Concerned
One or two woodlice appearing occasionally is not a cause for concern. If you are seeing them regularly and in multiple rooms, it is worth investigating more carefully.
Persistent woodlouse activity can indicate a moisture problem somewhere in the building — a slow leak, condensation behind a wall, rotting skirting board, or inadequate drainage. In that case, it is worth raising with your landlord or building manager.
Quick Identification Tip
Not sure if it is a woodlouse? Open Google Lens on your phone and point it at the bug. Woodlice are distinctive enough that identification apps get them right almost every time.