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Sowbugs / pillbugs

Sowbugs and pillbugs, sometimes called "woodlice," live outdoors, but they may occasionally enter homes in damp areas such as basements, first floor levels and garages. These creatures are a nuisance by their presence; they do not bite humans nor damage structures or household possessions. However, if present in large numbers, they can feed on young plants in greenhouses. Some may crawl into swimming pools and drown, causing complaints. Those that wander into homes usually die in a few days unless they find a moist place near a leaky pipe or in a damp basement, bathroom or laundry room.


Sowbugs are oval or slightly elongate with a flattened body and up to 3/4" long. They are wingless, brownish or slate gray, and possess well-developed eyes, seven pairs of legs and overlapping "armored" plates that make them look like little armadillos. Sowbugs have two tail-like structures on the rear end. Pillbugs are similar, except they lack the tail-like appendages and can roll up into a tight ball. Both are slow-moving crustaceans closely related to crayfish, shrimps and lobsters but not insects. The young resemble the adults, except they are smaller and lighter in color.

Life cycle and habits

Both sowbugs and pillbugs mate throughout the year, with most activity in the spring. The female carries the eggs, numbering from 7 — 200, in a brood pouch on the underside of her body. Eggs hatch in three to seven weeks and the young are white-colored. They remain in the brood pouch for six to eight weeks until they are able to take care of themselves. There may be 1 — 2 generations per year, with individuals living up to 3 years depending on weather conditions.

These creatures live outdoors, feeding on decaying organic matter and occasionally young plants and their roots. They may become pests in and around homes where flower bed mulches, grass clippings, leaf litter, rotting boards, trash, rocks and pet droppings are present. Adequate moisture is essential for their survival, and they group in masses to reduce water loss. On a hot day, they remain under objects on the damp ground and are active only at night due to lower temperatures and more humid conditions. They become inactive during the winter months except in heated buildings such as greenhouses.

These insects are mostly a nuisance. They cause little damage to living plants and are mostly involved in eating decaying plant material. They do not bite, sting, or transmit diseases, nor do they infest food, clothing or wood.

If their presence causes you problems, reduce moisture, particularly if they have migrated indoors.