Wood lice are small greyish, blackish or brownish Crustacea. Their bodies are flattened and consist of several plates with 19 pairs of appendages, including seven pairs of legs on their anterior part (pereion).
After mating, the female places her eggs in a liquid-filled incubator pouch, located under the pereion, in which the young develop. When they leave the pouch, the insects only have six of seven pairs of appendages on their pereion and will remain whitish in colour for several days before taking on their specific colouring.
Wood lice are nocturnal insects and shy away from light. Some, like pillbugs, manage to roll themselves into a ball for protection, and this may help fight evaporation. A number of other wood lice behaviours are indicative of their great need for moisture. Therefore, they will be less active on windy nights when water losses are probably greater. They have uropods (tube-like appendages), located at the end of their bodies, that allow them to absorb or discharge water. Wood lice can also detect the slightest change in relative humidity and tend to associate in groups. Lastly, unlike insects, they are not covered with a wax cuticle and moult in two stages over an interval of a few days. Despite all these adjustments, they are less well adapted than other invertebrates that do not live in an aquatic environment.
Wood lice exhibit positive thigmotaxis, i.e., they prefer to be in contact with a surface. Outdoors, they can, consequently, be found under a rock, bark, a bit of wood or recently-watered flower pots. This explains why they are usually seen in groups, although they may also be attracted by their own scent. Wood lice can be active throughout the year, indoors, but the adults are dormant outdoors during winter time.
Places where they can be found in the home
Since wood lice are in constant need of a very moist environment, they are often seen in basements. They do not do any damage indoors, although the owners of the house are usually not very happy about their presence. They normally feed on decomposing matter (organic waste, fruits and vegetables), microscopic fungi, algae and bacteria. Some wood lice are harmful to plants because they feed on the roots, stems or fruit. In Canada, only common rough wood lice (porcello scaber) behave that way. Wood lice sometimes burrow into the ground. Their numbers are usually higher in spring and summer due to humidity conditions at those times of year.
- Make an effort to control the moisture level, both indoors and around the house, by improving your drainage.
- Inspect your home to ensure that there is no accumulation of dead flies.
- It is best not to allow plant or other debris to accumulate near the house and to inspect your gutters regularly.
- Any wood introduced inside the house for the fireplace should be inspected; there may be wood lice living under the bark.
- Openings or cracks allowing access to the basement should be plugged.
Dehumidify the room by airing it out or installing a dehumidifier.
Wood lice are not insects (Hexapoda) but Crustacea. The latter usually have two pairs of antennae, but the first pair is atrophied in the wood lice that inhabit houses. Crustacea includes the order Decapoda (lobsters and shrimp) and Isopoda (wood lice). The term Isopoda refers to the fact that their legs are all alike (except for the pair of jawfeet). Wood lice are not covered with a true carapace like lobsters, however.
There are 44,000 species of Crustacea and 10,000 species of Isopoda. Most live in an aquatic environment, and some exist in close relationships with other animals. Wood lice differ from Crustaceans as they are mostly terrestrial, although a few of them are amphibious.
Some spiders can eat wood lice.
Some aquatic Isopoda are referred to as “sea centipedes” but they are closer to wood lice than they are to centipedes.