# Common rough woodlouse (Porcellio scaber) > A common, non-stinging terrestrial crustacean that eats decaying plant matter and prefers damp, sheltered places around houses and gardens. Source: https://insectscanner.com/species/common-rough-woodlouse/ (updated 2026-10-10) ## Is it dangerous? **Non-toxic.** Porcellio scaber is harmless to people. It does not sting, bite or deliver venom. Handling may leave a faint smell or a small amount of dirt; wash hands after handling. They are not known to transmit human disease. **Pets:** Generally harmless to cats and dogs. Pets might eat them out of curiosity; the woodlouse is not poisonous, though eating many could upset a pet's stomach. Some pets may avoid them because of their texture or smell. ## Quick facts - Scientific name: Porcellio scaber - Also called: Rough woodlouse, Sowbug - Order: Isopoda (Isopods) - Family: Porcellionidae (Porcellionid woodlice) - Size: 10-18 mm long - Colours: Grey, Brown, Mottled grey-brown - Habitat: Moist, shaded microhabitats: under logs, stones, leaf litter, bark, garden mulch, compost heaps, cellars and damp basements - Range: Native to Europe and now cosmopolitan through accidental human-assisted spread; found in temperate regions worldwide - Active: Primarily nocturnal and active year-round in mild climates; activity reduced in very cold or dry conditions - Lifespan: Typically 1-3 years for adults (some individuals may live longer) - Effect on plants: Detritivore / beneficial - Pest: no ## Overview Porcellio scaber is a widespread species of woodlouse (terrestrial isopod) often found under logs, stones, leaf litter and in damp basements or garden mulch. It is a detritivore that helps break down dead plant material and recycle nutrients. Adults are slow-moving, nocturnal and avoid bright, dry conditions. They are not insects but crustaceans adapted to life on land; females brood eggs and young in a pouch called a marsupium. Porcellio scaber is tolerant of a range of habitats and has been introduced globally from its native European range. ## How to identify it Adults are roughly oval, flattened top-to-bottom, with a distinctly rough, bumpy texture on the dorsal plates (pereonites). Colour ranges from grey to brown and sometimes mottled. Body length is typically about 10-18 mm. Unlike pillbugs (Armadillidium species) this species cannot roll into a tight ball and its uropods (rear appendages) project beyond the last body segment. - Rough, bumpy dorsal plates (uneven texture) rather than smooth - Cannot roll into a tight ball; body remains flattened when disturbed - Adult length about 10-18 mm and generally grey to brown in colour - Uropods (small tail-like appendages) extend beyond the rear margin of the body ## Lookalikes - **Common pillbug** (Armadillidium vulgare): Can roll into a tight ball (conglobate) and has smoother, more rounded plates; Porcellio scaber cannot fully roll up. - **Smooth woodlouse** (Porcellio laevis): Smoother and shinier dorsal plates and often larger; P. scaber has a distinctly rough texture. ## Life cycle - **Egg:** Eggs are retained and develop inside a brood pouch (marsupium) on the female until the young hatch. - **Juvenile (manca):** Young emerge from the marsupium as small, pale mancas that resemble adults but have only six pairs of legs; they gain the seventh pair and grow through several moults. - **Adult:** Sexually mature after several moults; adults continue to moult periodically and can live 1-3 years. ## Diet and predators - Young eat: Decaying plant matter, detritus and fungal material similar to adults - Adults eat: Primarily decaying leaves, wood, mulch and fungi; occasionally tender seedlings or soft fruit if abundant and other food is scarce - Predators of the young: Small predators such as centipedes, spiders, beetles, small amphibians and birds - Predators of adults: Birds, amphibians, small mammals (shrews, hedgehogs), centipedes and predatory ground beetles ## Effect on plants and gardens Feeds on decaying plant material and fungi; usually does not damage healthy living plants. In very large numbers and in very damp, young plantings or seed beds, they can nibble tender seedlings or fruit, but this is uncommon. ## Where and when to find it Look under stones, logs, flowerpot saucers, compost heaps, mulch, bark and in damp basements or cellars. Juveniles are found alongside adults in the same sheltered, moist microhabitats. - Best time: Night-time or after rain; active year-round in temperate regions but most visible during wet periods - Tips: Turn over damp refuges slowly and photograph from a low angle. Use a torch at night to spot them moving on the surface of mulch or leaf litter. ## Fun facts - Woodlice are terrestrial crustaceans, more closely related to shrimp than to insects. - Females brood their young in a pouch called a marsupium, where eggs develop in water retained by the mother. - They breathe using structures called pleopodal lungs or gills on the underside, which is why they need moist habitats. ## Frequently asked questions ### Are rough woodlice dangerous? No. Porcellio scaber are harmless to people and pets; they do not sting or transmit disease. ### Do rough woodlice bite? No. Woodlice have small mouthparts for chewing decaying plant matter and cannot bite people. ### Why are there woodlice in my house? They are attracted to damp, cool, dark places such as basements, cellars, bathrooms, or areas with damp wood or mulch. Moisture and easy shelter draw them inside. ### How do I get rid of woodlice? Reduce moisture and shelter: fix leaks, ventilate damp areas, seal entry points, remove leaf litter and wood debris near the foundation. Sticky traps or a shallow dish with wet folded cardboard can catch them for removal. Chemical control is rarely necessary. ### Do woodlice damage my plants or house? They mainly feed on decaying matter and help decomposition. They rarely damage healthy plants; they do not eat wood used in sound structural timber like termites do. --- More about this species: [iNaturalist](https://www.inaturalist.org/taxa/122238), [Wikipedia](https://en.wikipedia.org/wiki/Porcellio_scaber). Identify insects and spiders from a photo with the Insect Scanner iPhone app: https://apps.apple.com/app/id1543946563?pt=126685406&ct=web-markdown&mt=8 Identification from photos is never certain: don't handle insects you can't identify, and get medical advice for bites, stings or allergic reactions.