Sowbugs / Pillbugs

Common Names: Sowbugs / Pillbugs
Scientific Names: Class Crustacea, Order Isopoda

Introduction. These land-dwelling crustaceans are arthropods but not insects. They are worldwide in distribution. The British refer to these isopods collectively as woodlice. In the United States, the 2 most common species of sowbugs are Porcellio laevis and Porcellio scaber, both in the family Porcellionidae and of worldwide distribution.
Pillbugs are sometimes called roly-polies and get this common name because they roll up into a tight ball when disturbed. In the United States, the most common species is Armadillidium vulgare, which is in the family Armadillidiidae; it has worldwide distribution.

Recognition. Adult sowbugs reach up to 5/8 inch in length and are convex above but flat or hollow beneath. They are dark to slate gray, and have 7 pairs of similar legs and 2 pairs of antennae, (1 pair tiny, the other pair readily visible). Sowbugs have 2 prominent tail-like appendages (uropoda), which project out from the body on the posterior end. These crustaceans are capable of arching their bodies into a C-shape.
Adult pillbugs are 1/4 to 5/8 inch long and, like sowbugs, are convex above but flat or hollow beneath. They are slate gray in color and have 7 pairs of similar legs and have 2 pairs of antennae. Pillbugs are capable of rolling up into a tight ball when disturbed. The uropoda (paired terminal appendages on the posterior end) are short and rounded, and usually are not visible from above.

Biology. Sowbug and pillbug 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 to emerge from the pouch. The number of young per brood averages about 24 to 28 to 79+ and there are 1 to 3 broods per year, usually 2. Young sowbugs and pillbugs molt within a day or so after leaving the female's brood pouch and then molt every 1 to 3 weeks thereafter. They reach adulthood in about 20 weeks. Adults may live about 2 years.
Sowbugs and pillbugs 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.

Habits. Because water loss is such a problem, sowbugs and pillbugs 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, flowerpots, piles of grass clippings, flowerbed 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 and pillbugs are scavengers and feed on decaying organic matter, usually plant material. Indoors they cause no damage (except to plantings in greenhouses) and are considered a nuisance pest. Outdoors, they occasionally injure young plants by feeding on roots.
Cultural Control & Preventative Measures. The key to controlling sowbugs and pillbugs is to reduce or eliminate the moist areas, which make their survival possible. For example, remove piles of grass clippings and leaves, stacked boxes, lumber, firewood, and flower pots from the ground away from building foundations and provide adequate ventilation in crawl spaces and basements. This is best accomplished through strategic placement and operation of fans and dehumidifiers in these locations. Indoors, they can be removed with a vacuum cleaner.

Professional Control. Exterior perimeter barrier treatments with water-based and granular residual insecticide formulations are effective in markedly reducing sowbug and pillbug invasion if applications penetrate deep into activity zones in the mulch and soil next to the foundation. A Rottler technician will also target the exterior foundation wall and treat beneath any siding at the sillplate level using a residual liquid insecticide. Strategically-placed residual granular insecticides may also be used to help control these isopods in landscaping (flower and ornamental plant) beds near structures. A regular pest management service program may be required in cases where large populations of sowbugs and pillbugs are present and where landscaping conditions are conducive to their propagation.