Millipedes in the house: harmless visitors or a sign of damp?

In the morning they lie curled up on the cellar stairs, in the bathroom or behind the balcony door: dark, elongated creatures with lots of legs. Finding millipedes in the house is unsettling, yet they are harmless to people. The more important question is why they are turning up in your home – because damp is usually behind it.

In early summer, after warm and rainy days, they come indoors especially often. Here you will find out which species you are likely to meet, how to get rid of them without poison and how to keep your cellar and bathroom dry enough that they do not stay.

Why millipedes come into the house

Outdoors, millipedes live in leaf litter, compost, moss and under stones. They mainly eat dead plant material and so help to build humus. The environmental advice service of the City and Canton of Lucerne (Umweltberatung Luzern) stresses that they are useful decomposers rather than pests, but occasionally multiply massively for unknown reasons. When that happens they climb façades at night or die curled up in cellars.

They get in through cracks, cellar windows, light wells and open doors. Indoors they look for cool, damp places: cellars, laundry rooms, bathrooms and ground-floor rooms. In dry air they quickly lose water and die – which is why you often find dead, curled-up specimens.

In Swiss homes you will mainly come across these groups:

Strictly speaking, stone centipedes and house centipedes are centipedes, but in everyday German-speaking Switzerland they are all called Tausendfüssler. The house centipede is mostly found in warmer regions and in heated buildings.

1. Collect millipedes in the house instead of fighting them

The Umweltberatung Luzern recommends collecting them indoors every day with a dustpan and brush and putting them in the household rubbish. Alternatively, vacuum them up and empty the bag or container outside afterwards. If you would rather let them live, carry them in a jar well away from the house to a flower bed or under a hedge.

Do not squash cylindrical millipedes with your bare hands: some species release a fluid when threatened that can stain floors, rugs or skin. Wash your hands after collecting them.

2. Lower the humidity

Where millipedes feel at home, it is damp. That is the real problem, because the same moisture also encourages mould. The homeowners' association HEV Schweiz recommends keeping relative humidity between 30 and 50 per cent during the heating season and airing three times a day for 5 to 10 minutes with a through-draught, rather than leaving windows permanently tilted. Cellars also need to be aired correctly.

A hygrometer shows you how damp your cellar and bathroom really are. How to position and read one is explained in our guide how to use a hygrometer. Further measures are covered in the guide reduce humidity in your apartment.

For damp rooms, the Umweltberatung Luzern also mentions a dehumidifier or a light as help against these creatures.

3. Seal cracks and entry points

Fewer openings mean fewer visitors. The Umweltberatung Luzern advises sealing the cracks and holes they use to get in and keeping windows and doors closed when there are many of them about. Check in particular:

• cellar windows and light wells
• thresholds to the garden, terrace and garage
• skirting board joints on the ground floor
• openings for pipes in the cellar and laundry room

Report larger cracks in the masonry or faulty door seals to the property management or caretaker.

4. Outdoor barriers and diatomaceous earth

In a genuine invasion, measures outside the house help. According to the Umweltberatung Luzern, smooth barriers about 20 centimetres high along the house wall stop the millipedes from climbing. Where they gather, you can sprinkle diatomaceous earth bought from a pharmacy.

In the garden itself there is no need to fight millipedes – they do valuable work there.

5. Keep the cellar and bathroom dry and clean

Millipedes love damp hiding places. Take them away:

• Remove damp cardboard boxes, old newspapers and textiles from the cellar.
• Do not store leaves, firewood or compost against the house wall or in front of cellar windows.
• Do not leave laundry drying for weeks in a damp cellar.
• Air the bathroom well after showering and dry wet floors.
• Keep floor drains in the cellar and laundry room clean.

Earwigs and woodlice also look for damp hiding places – find out more in our guides earwigs in the house and woodlice in the house.

Common mistakes

• Insect spray in the cellar: poison does not solve the damp problem and is unnecessary against useful creatures.
• Only removing the creatures: without drier air and sealed gaps, new ones will follow.
• Windows permanently tilted: little air exchange, and walls that can become damp.
• Squashing millipedes: this can leave stains – collecting them is cleaner.

Priority Clean editorial teamOur cleaning team from Alberswil, Canton of Lucerne, shares hands-on experience from move-out, house, office and window cleaning across Central and Northwestern Switzerland.