Woodlice are members of the suborder Oniscidea from the order Isopoda. Depending on the species, the region where they live, as well as other criteria, woodlice have many different common names, some of which include: armadillo bug, boat-builder, butcher boy, carpenter, cafner, cheeselog, cheesy bobs, chiggy pig, doodlebug, gramersow, granny grey, pill bug, potato bug, roll up bug, roly-poly, sow bug, slater, or wood bug. There are more than 5,000 known species of woodlice, the most common of which are:
- Armadillidium vulgare (also known as the pill wood louse);
- Oniscus asellus (also known as the common wood louse);
- Porcellio scaber.
Description and distribution
A woodlouse is an isopod crustacean. It has a long, segmented exoskeleton, which is rigid and must be progressively shed as it grows, in order to allow further development. This moult is composed of 2 stages: first the back half, then, 2-3 days later, the front half. The reason why there are 2 stages to the moulting process has to do with minimizing the vulnerability of the woodlouse during the period, however short, it is without its armour. Depending on the species, woodlice will have up to 14 joined limbs, which give them flexibility. Generally, woodlice will be grey or brown in colour and measure around 1cm, although tropical species can grow up to 3 times larger.
Woodlice are spread all across the world, being an ancient crustacean species that has evolved from a water-based environment to being capable of living on land. Woodlice are actually the only crustacean that do not live in the water. Being so adaptable, woodlice can be found in a variety of habitats, from forests and jungles, to deserts. The only environments where they cannot live are the polar regions and the very arid deserts. Otherwise, the tough exoskeleton acts much like a shell, protecting the individual from variations in temperature, as well as humidity. A woodlouse’s habitat, therefore, only requires 2 main things: a reliable source of food; and a lack of complete dryness, which is something that woodlice cannot cope with. The latter is because they rapidly lose water, both through cuticles and by excretion. As such, woodlice will mostly be found in damp, dark places, such as under rocks, under logs, etc.
Breeding and dietary information
As for their breeding, female woodlice keep fertilized eggs in a marsupium on the underside of the body until they hatch. At that point, the offspring are called “manca” and have the appearance of tiny (±2mm), white adults curled up in balls. The females then seem to “give birth” to these offspring, as they deposit them in a safe place where they can continue to develop. Depending on the species, females can lay eggs up to 3 times a year, with approximately 50 eggs being laid at a time. Because development is slow, females will often remain close to the young, sometimes until they become adults. Despite this, many woodlice die while they are young. A woodlouse’s lifespan is of around 2 years, although some specimens are known to live up to 4 years.
Predators of woodlice are varied, made up of mostly insectivores, some of which are known to feed exclusively on them: spiders of the genus Dysdera and land planarians of the genus Luteostriata. Toads, centipedes, millipedes, and wasps also feed on woodlice.
Depending on the species, woodlice may have different defence mechanisms. Woodlice in the genus Armadillidium, family Armadillidae, for example, when threatened, roll up into an almost perfect sphere, hence the name pill bug or roly-poly.
When it comes to their dietary needs, most woodlice are detritivores, feeding on dead plant material, such as: mould, rotting leaves, rotting fruit, rotting wood, cellulose, etc. Some species, however, are omnivores (eating things such as animal faeces), and have a digestive system that allows them to eat even things that are poisonous to other species. It is only very rarely that woodlice will eat live plants. A handful of species of woodlice are carnivores, such as Tylos latreillei, from the genus Tylos, which lives on the seashore and feeds on sand hoppers.
Woodlice as pests
Although they are normally considered to be beneficial in gardens, seeing as they play a role in controlling certain pests, as well as in producing compost and overturning the soil, breaking down dead vegetation and organic matter, woodlice can also come to be considered pests themselves; they have been found to feed on cultivated plants, such as ripening strawberries or tender seedlings.
Indoors, woodlice may cause superficial damage to wallpaper, decorations and possibly furniture. Despite this, the idea that woodlice will chomp on all the woodwork and wooden furniture that you have in the house is a common misconception; woodlice only eat what has already started to decay, so if you have a serious infestation, you can take that as a sure sign that your home has sufficient damp and decaying wood for them to thrive on. Woodlice also do not transmit any diseases, and are thus completely harmless to humans.
They can be easily eliminated, but as with any other insect, it is better to prevent such an infestation, than having to deal with getting rid of it. For preventive measures and ways in which to avoid an infestation, you can check our related article about how to ‘Prevent infestation with Wood Lice’. If you are already dealing with such an issue and you need advice regarding ways of eradicating this pest, visit our article about ‘How to get rid of Wood Lice’, and find out what types of methods of control you can use.