Woodlice and Silverfish

Woodlice and Silverfish: What They Are and How to Deal With Them

Woodlice and silverfish are two of the most common uninvited guests in UK homes, yet many people know surprisingly little about them. Both favour dark, damp spots and tend to scuttle away when disturbed, but beyond these shared habits, they are quite different creatures with different needs and behaviours.

If you keep finding these creatures around your home and want to know whether you should be concerned, understanding what attracts them and how they live will help you decide on the right approach.

Woodlice: Crustaceans, Not Wood Pests

Despite appearances, woodlice are not insects. They belong to the crustacean family, making them relatives of crabs, lobsters and prawns. This ancestry explains their most notable requirement: moisture. Unlike most land animals, woodlice breathe through gill-like structures and will dry out quickly in warm, dry conditions.

Their common name is misleading. Woodlice do not eat or damage sound timber. In the wild, they feed mainly on decaying plant matter, fallen leaves and fungi. They play a useful role in gardens by breaking down organic material and returning nutrients to the soil. Occasionally they may nibble on young seedlings or soft plant shoots, but this is rarely significant. However, finding woodlice near wooden structures can sometimes indicate that dampness or decay is already present, which may itself warrant investigation.

Outdoors, woodlice shelter during the day under stones, logs, plant pots and in compost heaps. They emerge at night to feed. When conditions outside become unfavourable, whether through drought, heavy rain or cold weather, they sometimes wander indoors. They commonly turn up in kitchens, bathrooms, utility rooms or cellars where humidity tends to be higher.

Finding the odd woodlouse indoors is normal and not a cause for concern. They struggle to survive in typical household conditions, though they can persist longer if they locate a suitably damp corner such as beneath a leaking pipe or in a poorly ventilated cupboard. A few woodlice in winter simply indicate they have found a gap or crack to enter through while seeking shelter.

Larger numbers appearing regularly could point to a damp problem, a significant entry point, or simply favourable conditions close to your exterior walls. Check around doors, windows, airbricks and pipe entry points for gaps. Addressing any sources of excess moisture, such as leaking pipes or poor ventilation, will make your home less appealing to them.

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Silverfish: Resilient Survivors

Silverfish are true insects, though they belong to one of the oldest insect groups on Earth, predating the dinosaurs by millions of years. Their distinctive silvery scales, tapering bodies and rapid, wriggling movements give them their name.

Like woodlice, silverfish prefer humid environments, but they are considerably better adapted to indoor life and can establish themselves in buildings more readily. They are most active at night and tend to hide in cracks, behind skirting boards, under baths and in airing cupboards during the day.

Silverfish feed on starchy materials. This includes paper, wallpaper paste, book bindings, cardboard, cotton, linen and certain food products like flour and oats. In small numbers they cause little damage, but a well-established population can gradually harm books, documents, photographs and textiles over time.

They reproduce slowly compared to many household pests, so infestations tend to build up gradually rather than appearing suddenly. A few silverfish spotted occasionally is common in older properties and may not require any particular action beyond general good housekeeping. It is worth noting that some individuals with sensitivities may experience allergic reactions to silverfish scales or droppings, though this is uncommon.

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Practical Steps to Reduce Numbers

For both woodlice and silverfish, reducing moisture and humidity is the most effective long-term approach. Both species depend on damp conditions to survive and reproduce, so a drier home will naturally become less hospitable to them. Ensure bathrooms and kitchens are well ventilated, fix any dripping taps or leaking pipes promptly, and consider using a dehumidifier in persistently damp rooms.

Sealing gaps around pipes, doors and windows will help prevent woodlice from entering. Clearing debris, leaf litter and rotting wood from directly against exterior walls removes potential shelter sites close to your home.

For silverfish, reducing available food sources helps. Store dry goods in sealed containers, vacuum regularly to remove dust and debris, and avoid leaving damp towels or clothes lying around.

Sticky traps placed along skirting boards, beneath sinks and behind appliances can help monitor silverfish activity and catch some individuals. Various insecticidal sprays and powders are available from hardware shops and garden centres for more persistent problems. Integrated pest management approaches, which combine physical barriers, environmental controls and targeted treatments, are increasingly recommended by professionals. Always follow product instructions carefully and keep treatments away from children and pets.

When to Seek Professional Help

Most woodlice and silverfish problems can be managed with the steps above. However, if you are finding large numbers regularly despite taking these measures, or if you suspect a significant damp issue, professional advice may be worthwhile.

Pest control services can identify entry points and harbourage areas you may have missed. For damp problems, a surveyor can assess the cause and recommend appropriate remediation.

The British Pest Control Association maintains a directory of professional pest controllers on its website, which can help you find a reputable local service. Local councils in England, Scotland and Wales may also offer pest control services, though charges and availability vary. Check your council's website for details of what is provided in your area.

Neither woodlice nor silverfish pose significant health risks to humans. They do not bite, sting or transmit disease. While finding them in your home can be unwelcome, they are generally more of a minor nuisance than a serious problem.

The Next Step

Now that you have read through the advice above, you might want to put it into practice. Our Treatment Guide lets you enter the type of pest and where it is causing problems to get a tailored removal guide. Covers both home remedies and shop-bought treatments. Try it now →