Common Name: Sowbug
Scientific Name: Various
These land-dwelling crustaceans are arthropods but not insects. They are worldwide in distribution. In the United States, the 2 most common species are Porcellio laevis Koch and P. scaber (Latreille), both in the family Porcellionidae and of worldwide distribution.
Adults up to about 5/8″ (16 mm) long, convex above but flat or hollow beneath. Color dark to slate gray. Typical of crustaceans, sowbugs with 7 pairs of similar legs; 2 pairs of antennae, 1 tiny, the other readily visible; body dorsoventrally flattened (top to bottom). With 2 prominent taillike appendages (uropoda) which project out from body on posterior or rear end. Capable of rolling up into only a very loose ball when disturbed.
(1) Pillbugs (order Isopoda) with uropoda (taillike appendages) short and rounded, usually not visible from above, can roll into tight ball.
(2) Centipedes (class Chilopoda) with 15 or more pairs of legs.
The eggs are deposited and hatch within the brood pouch or marsupium on the underneath side of the body. It usually takes about 45 days for the eggs to develop, hatch, and the young sowbugs to emerge from the pouch. The number of young per brood averages about 24 (range to 88) and there are 1-3 broods per year, usually 2. Young sowbugs molt every 1-2 weeks and reach adulthood in about 20 weeks.
Adults may live about 2 years. Sowbugs are confined to areas of high moisture because they lack both a closing device for their respiratory system and an outer waxy layer on their exoskeleton to prevent excessive water loss. Their nocturnal habit helps to reduce water loss.
Because water loss is such a problem, sowbugs are inactive during the day and remain hidden under objects to reduce moisture loss. During the day, they can be found around buildings in such places as under trash, boards, rocks, flower pots, piles of grass clippings, flower-bed mulches, and other decaying vegetation. They occasionally enter buildings via door thresholds, especially homes with sliding glass doors on the ground level.
Indoor invasion typically means that there is a large population immediately outside the building. Usually they do not survive indoors for more than a couple of days unless there are moist conditions and a supply of food present. Sowbugs are scavengers and feed on decaying organic matter, usually plant material. They cause no damage and are considered a nuisance pest indoors. Outdoors, they occasionally injure young plants.
The key to controlling sowbugs is to reduce or eliminate the moist areas which make their survival possible. For example, remove piles of grass clippings and leaves, store boxes, lumber, firewood, and flower pots off the ground, and provide adequate ventilation in crawl spaces. Indoors, they can be removed with a vacuum.
Application of appropriately labeled residuals can be made to building foundation walls, perimeter flower and/or ornamental planting beds, unfinished basements, and crawl spaces. Wettable powder and micro encapsulated formulations are best, but dusts are also good in drier crawl spaces.