Turn over a log in the woods or lift a flowerpot in the garden and you are likely to see woodlice scuttling for cover. The minibeasts have seven main body segments each with a pair of legs which shows they are not lice and not even insects, they are crustaceans, relatives to crabs and shrimps.
Unlike crabs and shrimps, the limbs are all the same and this is the root of their scientific name Isopoda, from the Greek for equal foot.
Specimens trapped in amber show that woodlice have been around in their current form since the time of the dinosaurs, probably much longer. In those 60 million years they have managed to colonise almost every habitat, from under your garden pots to tropical rainforests, there are even woodlice that have adapted to living in deserts and on high mountain slopes.
Wherever they live, the one thing woodlice need is damp, their outer cuticle is not water proof and they lose water easily. This why you tend to find them hiding in dark damp places. The flattened body and many legs allow them to crawl into very tight spaces.
There are thousands of species of woodlouse, at least 35 are found in the UK but you are most likely to find the dull grey Rough Woodlouse and the brownish Shiny Woodlouse in Devon, possibly also the Striped Woodlouse which is shiny but has more colour variation.
In common with most crustaceans, the woodlouse body has two main parts behind a small head with two antennae. The front seven segments each have a pair of legs. The ‘tail’ section or pleon has six segments but no legs. If you turn a woodlouse over and it doesn’t curl into a ball, you might see small white appendages under the ‘tail’ section, these are thin skinned breathing appendages that act like lungs. The cuticle on the underside of the main body is also able to allow oxygen and carbon dioxide to pass in and out, but only if it is damp.
Female woodlice hold their fertilised eggs in a sac on their underside called a marsupium where the developing embryos received oxygen, water and nutrients. When they hatch, the babies may remain protected for some time before emerging as small, white woodlice with only six pairs of legs. As they grow, they have to shed their exoskeleton. They do this in two stages, first the pleon cuticle is shed, and then the main body. You may see woodlice with one half white, this is where the old cuticle has separated but not been shed.
Woodlice play an important part in maintaining habitats because they are detritovores, they feed mainly on dead plant material, recycling the nutrients. Occasionally some will feed on very delicate seedlings but they rarely cause any harm in the garden. The woodlice themselves are eaten by centipedes, shrews, toads and spiders. The Woodlouse Spider, Dysdera crocata, has particularly strong fangs that can pierce the shell of a woodlouse.
Woodlice are ubiquitous and fascinating creatures and they have acquired a huge range of common names, Bibble Bug, Cheesy-bug, Chiggy Pig, Roly-Poly or Tank are just some of the regional names. Woodlice are ideal starter species for engaging children with nature. How many different types live in your garden? You can keep them for a short period for closer study. They don’t ask for much, somewhere cool, dark and damp, from a plastic box to an aquarium/terrarium with a layer of material gathered from where they were collected, but they should be returned to their natural home eventually.
Ed Dolphin
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