Sowbugs (Oniscus asellus) and Pillbugs (Armadillidium vulgare) are the only crustaceans that have completely adapted to spending their whole life on land. They have oval bodies, convex above and flat or hollow beneath. The common pillbug and the dooryard sowbug are worldwide.
They like moist locations and are found under objects on damp ground, as well as under vegetable debris of all kinds. They are mostly active at night.
Sowbugs can be distinguished from a pillbugs by the fact that they cannot roll up into a tight ball like a pillbug. As well, the sowbug has two tail-like appendages that the pillbug does not have.
Sowbugs and pillbugs will at times invade damp basement areas as well as the first floors of houses. When this occurs they are most likely always present in large numbers in the soil and under plants immediately outside the house.
Sowbugs and pillbugs normally feed on decaying vegetable matter. They become inactive during the winter months although this may not be the case in artificially heated buildings such as greenhouses.
The female carries her young in a pouch called a marsupium on the underside of the body. She gives birth to very many white living young. There are usually one or two generations per year depending on environmental conditions.
Leaves, grass clippings, mulch, boards, stones and similar material close to the building should be removed since these may harbour sowbugs and pillbugs. Avoid excess moisture in basements or crawlspaces, and rep air any cracks or openings into your home.
Sowbugs and pillbugs can become a problem in and around the home. Though they don’t cause major damage, they can be a pest.