You've spotted woodlice in your garden, compost heap, or perhaps an occasional one in the corner of a damp room. What are they actually eating, and should you be worried? The properly short answer: woodlice are detritivores — they eat decaying plant matter, fungi, and dead organic material. They're genuinely some of the most useful animals in any garden ecosystem, and far from being pests, they're nature's recyclers. This guide covers what woodlice eat, their role in healthy ecosystems, and how to live alongside them.
The Quick Answer
Woodlice primarily eat:
- Decaying plant material — fallen leaves, rotting wood, dead plant stems, compost
- Fungi — moulds, mushroom material, microscopic decomposers
- Dead insects and animal matter — they're properly opportunistic scavengers
- Their own droppings (coprophagy) — extracts maximum nutrition from food
- Occasionally tender plant material — seedlings or soft fruit, particularly when decaying matter is scarce
Their role is properly fundamental to soil health: they break down dead organic matter into nutrients plants can use. Without woodlice and similar detritivores, garden leaf litter would accumulate indefinitely and soil nutrient cycling would slow dramatically.
What Are Woodlice, Exactly?
Woodlice (also called pill bugs, sow bugs, slaters, or roly-polies depending on where you grew up) are properly terrestrial crustaceans — relatives of crabs, lobsters, and shrimp that evolved to live on land. They belong to the suborder Oniscidea, with approximately 3,700 species worldwide adapted to terrestrial life.
Despite often being mistaken for insects, woodlice are properly distinguished from insects by:
- Seven pairs of legs (insects have three pairs)
- Two pairs of antennae (insects have one pair, often hidden)
- Crustacean ancestry — they're properly more closely related to lobsters than to beetles
- Modified breathing structures (pseudotracheae) that still require humid environments
The UK's Common Woodlouse Species
In British gardens, you'll most commonly encounter these five species — sometimes called the "famous five" by UK woodlouse enthusiasts:
Common Rough Woodlouse (Porcellio scaber)
Properly the most widespread UK species. Grey-brown body with a rough, dimpled exoskeleton (hence "rough"). About 12-17 mm long. Active under stones, logs, and compost heaps. The dietary generalist of the group — eats everything from rotting wood to leaf litter to fallen fruit. P. scaber is also widely kept in the hobby with selectively-bred colour morphs available. Browse our Porcellio collection for the bred variants.
Common Shiny Woodlouse (Oniscus asellus)
Distinguishable from P. scaber by its smooth, shiny exoskeleton with paler patches. Slightly larger than the rough woodlouse, properly up to 18mm. Prefers consistently damp environments — compost heaps, under bark, deep leaf litter. Diet similar to P. scaber but more dependent on truly decaying material than tender plant parts. See our Oniscus collection for related hobby species.
Common Pygmy Woodlouse (Trichoniscus pusillus)
Properly tiny — only 4-5mm. Pink to reddish-brown colour. Found in extremely damp habitats — under wet stones, leaf litter, beneath flowerpots. Often missed because of its small size. Eats fine organic debris and microscopic decomposing material.
Common Striped Woodlouse (Philoscia muscorum)
Smaller than the rough or shiny species (~10mm) with distinctive dark stripes running along its back. Properly fast-moving compared to other woodlice. Prefers slightly drier habitats than its cousins — found in dry leaf litter, meadows, and shorter grassland. Diet emphasises fungi and dry leaf material.
Common Pill Bug (Armadillidium vulgare)
The famous "roly-poly" — the species that can roll into a complete ball (conglobation) when disturbed. Distinguishable from the other woodlice by this behaviour and by the slightly more rounded body. Properly common in gardens and disturbed habitats throughout the UK. A. vulgare is also extremely popular in the hobby, with selectively-bred colour morphs (Jelly Bean, Magic Potion, Saint Lucia, and many others) available. Browse our Armadillidium collection for hobby variants.
Feeding Behaviour in Detail
How Woodlice Eat
Woodlice have specialised mouthparts that allow them to scrape and chew tough plant material — particularly the cellulose and lignin in decaying wood that most animals can't digest. They process this material slowly, helped by gut bacteria that break down the toughest plant compounds.
Properly interesting feeding behaviours include:
- Coprophagy — woodlice eat their own droppings to extract additional nutrients. This isn't a sign of stress or starvation; it's a normal adaptation that maximises nutrient extraction from low-quality food
- Selective feeding — they prefer leaves at specific stages of decay. Freshly fallen leaves are properly less palatable than partially decomposed ones; properly rotted material is preferred over either
- Calcium-seeking — woodlice need calcium for their exoskeletons and will graze on limestone, eggshells, snail shells, and similar mineral sources
- Mostly nocturnal feeding — they typically feed at night or in dim conditions when humidity is highest
In Gardens
In gardens, woodlice properly thrive on the abundant organic matter — compost heaps, leaf piles, fallen logs, mulched beds. They're processing this material into the nutrients plants need.
The vast majority of garden woodlice activity is properly beneficial. They:
- Break down leaf litter rapidly
- Speed up compost decomposition
- Contribute to soil structure
- Provide food for hedgehogs, shrews, robins, frogs, and other garden predators
- Help recycle nutrients from dead plant material back to living plants
Occasionally — and only occasionally — they'll nibble on tender plant material. This typically happens when decaying organic matter is scarce. Seedlings, very ripe strawberries, and soft fruit are the usual targets. Even then, the damage is properly minimal compared to slugs or other actual garden pests.
In Homes
When woodlice find their way indoors, they're properly looking for moisture rather than food. They can't eat dry materials effectively — wallpaper paste, paper, cardboard only get nibbled when extremely damp. Their indoor diet is genuinely limited.
Woodlice in homes typically indicate:
- A damp area (leaking pipe, condensation problem, wet timber)
- Garden material brought inside (firewood, plants, soil)
- Easy entry points (cracks, gaps around windows or doors)
The good news: woodlice don't bite, don't carry human diseases, don't damage structural timber (they only eat already-rotting wood, not sound timber), and don't lay eggs indoors in any meaningful way. They're genuinely some of the most harmless creatures you'll find indoors.
Living Alongside Woodlice
If you find woodlice indoors and want to discourage them, the right approach is properly to address what's actually attracting them — moisture and habitat — rather than reaching for chemicals.
Humane Removal Options
- Gentle relocation — sweep them onto a piece of paper or into a small container and release outside. Compost heaps, under garden stones, or beneath shrubs all work
- Address moisture — find and fix the damp problem they were attracted to (leak, condensation, wet timber). Without moisture, woodlice properly can't survive indoors
- Seal entry points — gaps around windows, doors, vents, and pipes
- Improve ventilation — particularly in bathrooms, basements, and ground-floor rooms
- Remove damp materials — soggy cardboard, decaying mulch near foundations, leaf piles against walls
Properly avoid chemical treatments (insecticides, woodlice powders, similar products) unless dealing with a genuinely unusual infestation. Most "woodlice problems" resolve with moisture management alone.
If You're a Gardener: Welcome Them
If anything, encouraging woodlice in your garden is properly beneficial. Healthy soil ecosystems need detritivores, and woodlice are properly one of the most efficient. To support garden woodlice populations:
- Maintain compost heaps
- Leave fallen leaves in some areas rather than removing all of them
- Add log piles for habitat structure
- Avoid pesticide spraying near woodlice habitat
- Mulch garden beds with organic material
From Garden Curiosity to Hobby Keeping
If garden woodlice have caught your interest, you might be surprised to learn that thousands of UK hobbyists keep isopods (the broader category that includes all woodlice) as pets. They're properly low-maintenance, fascinating to observe, and the selectively-bred colour morphs are genuinely beautiful.
The hobby covers everything from beginner-friendly British native species to spectacular Vietnamese cave morphs:
- For beginners: Porcellio scaber Mix — selectively-bred colour variants of the UK-native rough woodlouse. Properly easy to keep, genuinely UK-native, and visually distinctive
- For colour variety: Dairy Cow Isopods (Porcellio laevis) — black-and-white piebald colouration, large and visible
- For "roly-poly" enthusiasts: Armadillidium collection — the conglobating pill bugs in many selectively-bred morphs
- For ambitious keepers: Cubaris (Rubber Duckies, Panda Kings, Crazy Horse) — spectacular Southeast Asian cave morphs that look genuinely unlike anything in your garden
Keeping isopods doesn't require much equipment, doesn't take much space, and can be a properly absorbing hobby for adults and a great educational pet for children. See our guide to setting up and selecting your first isopods for genuinely beginner-friendly guidance.
Interesting Woodlouse Facts
- Seven pairs of legs — fourteen legs total, on seven thoracic segments. This is properly the defining feature of the order Isopoda
- Crustacean lineage — woodlice's closest living relatives are marine isopods (deep-sea giants like Bathynomus) and aquatic crustaceans like crabs and lobsters
- Two-stage moulting — unlike most arthropods which shed in one go, woodlice properly moult in two stages: back half first, front half a few days later. This lets them stay partly mobile while moulting
- Specialist breathing — they breathe through modified structures (pseudotracheae in some species, gill-like pleopods in others) that genuinely require humid conditions to function
- Conglobation — only certain woodlouse families (Armadillidiidae particularly) can roll into a complete ball. The "famous five" includes one true conglobator (Armadillidium vulgare) and four species that can't roll up
- Regional names — UK regional names for woodlice include slater, chiggypig, gramfy, monkey-pea, and dozens more. Properly more regional names than almost any other British animal
- Long-lived — common UK woodlice can live 2-3 years; some larger hobby species reach 5+ years
- Eaten by humans (rarely) — while UK woodlice aren't eaten, deep-sea giant isopods (Bathynomus) are occasionally served as a culinary novelty in parts of Asia. Not generally recommended as food
The Honest Verdict
Woodlice are properly some of the most maligned but ecologically valuable animals in the UK. They're not pests in any meaningful sense — they don't damage homes, don't carry diseases, don't bite, and they perform essential work in soil ecosystems. The "what do woodlice eat" question is genuinely a good entry point to appreciating one of nature's most efficient recycling systems.
For setup essentials if you want to keep them as pets, browse our accessories collection. For setup guidance, see our first isopods guide. To browse the full range of species available in the UK hobby, see our isopods collection.
Whether you encounter them in your compost heap, find one in the bathroom, or end up keeping a colony as fascinating low-maintenance pets — woodlice are properly worth appreciating rather than fearing. They've been doing their quiet ecological work for hundreds of millions of years, and they're properly very good at it.
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