Not the most exciting of creatures, woodlice creep about the garden, but they are a useful part of the local ecosystem.
Chances are that if you turn over a log or two or a heavy plant container, you’ll find a little tribe of woodlice beneath, scattering away in the light. Harmless, not very exciting, with their dark grey backs looking like armour, they’re just a part of the garden all year through.
But they are a very useful part of your garden’s eco-system. They chew through leaf litter, breaking it down, and without this little army there would be higher piles of dead leaves around. They’re useful in the compost heap too, doing the same job, breaking down plant matter, and they eat fungi.
They’re also part of the food chain, providing a meal for centipedes, some spiders, for shrews, toads, and even a few birds such as the wren.
They are crustaceans, related to crabs and shrimps. They have evolved to be able to survive on dry land by hiding in dark, moist places such as under your plant containers, in your compost heap, log pile or any dead wood that’s lying around.
There are five species in the British Isles and their names together with the botanical names are longer than they are: the common rough woodlouse Porcellio scaber, the common shiny woodlouse Oniscus asellus, the striped woodlouse Philoscia muscorum, the common pill woodlouse Armadillidium vulgare and the common pygmy woodlouse Trichoniscus pusillus.
There are about 30 species of woodlouse that are much rarer, but of these five commonest species, there’s every chance that you have one or more of them in your garden. Across the globe there are about 35,000 species of woodlice!
A woodlouse has 14 legs and its outer shell is called an exoskeleton. When it grows too big for its shell it moults to allow a bigger shell replace the smaller one. This happens in two stages: the back half is shed first, and a day or so later the front half falls off.
They have a pair of antennae to help them get around, and two small ‘tubes’ called uropods that stick out of the back of their bodies. These help them navigate and for some it’s an extra protection, used to produce chemicals to discourage predators. As they came from water originally they still breathe using gills.
The females have an internal fluid-filled brood pouch where they incubate their eggs. The young hatch inside the pouch and remain there until they can survive alone.
As you will have noticed when you lift a log, stone or plant container, they tend to group together. They will emerge particularly at night especially when it’s rather damp, and they don’t go far.
A common woodlouse can live for three or four years. That means they each get through a lot of dead leaves and plant material, so they are one of your unpaid garden helpers. If you find one indoors, it will curl up into a ball if disturbed; just put it outside – they don’t bite!
As they like damp areas they may get into damp bathrooms and toilets so seal up gaps with good sealant, looking at doors and windows. They will mostly die in your home as they are soon dehydrated by our warm, dry rooms. Repoint walls and clear vegetation from the base where woodlice can get in through any cracks.
Pesticide prays and insect dust products are available for severe cases but woodlice are too useful outside, so if you just see one or two just try putting them in the garden under a log or pile of leaves instead of using chemicals on them.