Pillbugs and sowbugs are two tiny pests considered to be occasional invaders because they will enter homes and buildings, but survive better outdoors - unless the find a wet or very damp area in which to live.
In fact, these two common pests are not insects or arthropods. They are crustaceans and are, in fact, the only crustaceans that have adapted to living completely on land rather than water. Because of this, pillbugs and sowbugs have more characteristics and appearance similar to crayfish or lobsters than to insects.
Pillbugs and sowbugs look the same:
- 1/4 to 1/2 inch long
- 7 pairs of legs
- 2 pairs of antennae, though one pair cannot be easily seen
- dark gray to white; may be solid colored or patterned.
- rounded bodies are convex on top and concave on bottom
... but are different:
- The many segmented body of the pillbug enables it to roll into the tiny ball in which it is often seen, and for which it is named - "pill" or, more commonly, "roly-poly."
- Sowbugs have two tail-like appendages extending from the rear end of bodies.
Both sowbugs and pillbugs:
- need moisture to survive.
- can live up to three years in optimal conditions.
- are most commonly found outdoors underneath stones, rocks, boards, leaf litter and other items lying on the ground where it is moist.
- may enter homes and buildings at ground level, into damp basements, or in crawl spaces. They will only survive, however, if moisture is found.
- generally come out from their harborage only at night - unless their shelter is disturbed.
- are scavengers. They feed on decomposing organic matter such as leaves and logs. They may also feed on young plants as well as the skin of cucumbers.
- are harmless to people, but can damage plants and seedlings with their feeding.
Prevention and Control of pillbugs and sowbugs
- Exclusion - As with most insects, rodents or other pests, one of the best ways to keep pillbugs and sowbugs from invading your home is building them out. That is, sealing all cracks, crevices and gaps in the foundation; around vents, cables and wires and around doors and windows (especially at thresholds); and repairing and maintaining screens and keeping doors and windows shut. Particular emphasis should be paid to the ground level areas, as this is where the pests most frequently enter.
- Moisture Reduction - Because thesee pests cannot survive without moisture, repairing and eliminating any areas in the home that are wet or damp (such as basement areas, leaky pipes, cracked foundation areas, etc.) will help keep these pests from surviving or reproducing even if they do enter your home. It is also helpful to ensure that the property is graded away from the home so that water flows away rather than accumulating near the foundation.
- Sanitation - Pillbugs and sowbugs will harbor in clutter, especially piles that have gotten moist from sitting. Because they feed on organic matter, they may also seek out such areas for food.
- Indoor Chemical Control - Once these pests enter the home, insecticides will be of little use. Rather they can be controlled by simply vacuuming or sweeping when seen and controlling moisture and sanitation to disable survival.
- Exterior Chemical Control - A perimeter application of an insecticide labeled for sowbugs/pillbugs and the area in which it is to be used can provide some preventive control in keeping these, and other occasional invaders, out of your home.
According to the University of Kentucky, insecticides may be applied "along the bottom of exterior doors, around crawl space entrances, foundation vents and utility openings, and up underneath siding. It may also be useful to treat along the ground beside the foundation in mulch beds, ornamental plantings, etc., and a few feet up the base of the foundation wall. (Heavy accumulations of mulch and leaf litter should first be raked back to expose pests for treatment.) Insecticide treatment may also be warranted along foundation walls in damp crawl spaces and unfinished basements."
Always read and follow all label directions when using any chemical pesticide.