They are in fact crustaceans, relatives of the shrimp, that have adapted to life on land. Called a woodlouse singularly, they are harmless to humans - they don’t sting, bite, or transmit any diseases, so if you find them indoors, you shouldn’t be concerned for your health. Often, they have wandered into your home accidentally, or have perhaps got caught on your pet’s fur and fallen off onto your floor.

Bibble-bug, chisel-hog, palmer-worm, monkey-pea, chuggy-pig, roly-poly, Johnny-grump and slater - all extraordinary names they have collected over the centuries!

Apparently, children secretly raced woodlice on the back of pews at boring Sunday sermons by coaxing their runners – identified by paint specks – to greater speed by tickling them with feathers. Too much urging and a competitor curled into a ball and suffered disqualification. They have even been kept as pets in old fish tanks or plastic storage containers with a layer of damp compost or leaf litter, where they will live on kitchen peelings and can be ignored for days without harm. They are a good pet to study, and excellent pets if you have an allergy to the usual fluffy ones - they don’t bark, don’t scratch the furniture and don’t leave poo on the carpet - what more could you ask for?

They are terrestrial isopods of the family Oniscidea, which have invaded earthly habitats from watery environments. Most species can still tolerate submersion in water, with some land species and cave isopods escaping into the water in pools or puddles when disturbed. Others have colonized dry environments, even deserts, by decreasing their permeability to water loss and changing foraging activity to different times of the day. The average lifespan of a woodlouse is 2 years, with some living up to 4.

Most are small to medium sized (1.2–30 mm), with 14 legs and two long antennae, and around 5000 species are distributed worldwide. There are several forms: runners, which have large eyes, long legs, and sometimes change their colours to suit their environment, rollers, capable of rolling into a tight ball when disturbed, clingers, less mobile than the previous ones with flattish bodies which they press down on flush surfaces, and creepers, which have developed to live in narrow gaps, caves, etc. Their body surface is covered by setae (fine hair which helps them sense movement), scales and glands. The one we mostly see is small and oval-shaped, usually around 15mm in a brown/grey colour, with numerous horizontal ridges running along them — and will roll up into a tight ball if threatened.

A hungry world

They face a hungry world, sharing their habitat with spiders, beetles and centipedes who will all eat them, and mature woodlice can also turn cannibal in the mating season. They are a main food source for shrews, but foxes and owls will also take them. Eggs are produced in the spring, and these are retained inside the female’s body until they hatch. The babies, known as mancas, are kept in a brood pouch underneath the female for a few days before they disperse, and will shed their outer shells several times as they grow. They become adults by late summer before reproducing in their second year.

In small numbers, they don’t pose much of a problem, but a woodlice infestation can become difficult to handle, and you need to understand why they seek the indoors, as it could mean an underlying damp problem. Clustering around your guttering could mean a leaky gutter, and they are attracted to any damp wood, mould or rotting things inside your home. To the surprise of many, woodlice perform an important duty outside by eating decaying matter such as dead plants, fallen or decaying fruit and even animal droppings, and large numbers often occur in compost heaps, where they help break down plant material.

Getting rid of woodlice before an infestation starts is very simple – you simply sweep up those rolling balls when you see them and use an insecticidal powder or spray around likely points of entry. However, if you’re seeing them all over the place, then you need to take more drastic measures and call in the experts.