Roly polys, commonly known as pill bugs or woodlice, are terrestrial crustaceans, not insects, making them related to shrimp and crabs. They are unique as the only crustaceans fully adapted to land, though they still require moisture to breathe through gills. Their presence indicates a dark, moist habitat. Their habit of curling into a defensive sphere when disturbed earned them the “roly poly” nickname. Generally, they are harmless detritivores, feeding on decaying organic matter.
Health and Safety Concerns
Roly polys do not pose a threat to human or pet health. These crustaceans lack the ability to bite or sting, and they do not possess venom or toxins. Their defensive mechanism is simply to roll into a tight ball, a behavior known as conglobation, which protects their softer undersides.
Roly polys do not transmit common household diseases. Their presence indoors indicates a moisture issue, as they seek damp environments like basements, but they are not a health hazard. While high concentrations of arthropods can potentially contribute to allergens, this is rare. They are safe to handle and pose no physical danger.
Impact on Gardens and Structures
Roly polys consume dead and decaying plant material, which is a beneficial activity. However, their diet shifts when conditions are overly damp or when decaying food sources become scarce. When populations are very large, they may occasionally become minor pests by nibbling on tender new growth.
They can damage delicate young seedlings, soft roots, or ripe fruits resting directly on the soil, such as strawberries. This damage appears as small holes or chew marks, usually occurring at night when they are most active. They do not damage sound structural wood, but they congregate under damp woodpiles or mulch near foundations.
The Role of Roly Polys in the Ecosystem
The primary ecological function of roly polys is as decomposers, making them valuable contributors to soil health. They break down dead leaves, fallen wood, and other organic debris, initiating nutrient cycling. This consumption of detritus releases essential nutrients like nitrates, phosphates, and potassium back into the soil, making them available for living plants.
These crustaceans also sequester heavy metals from the soil. They ingest toxins like lead, cadmium, and arsenic and crystallize them into spherical deposits within their mid-gut. This process concentrates the pollutants, preventing them from leaching into groundwater and stabilizing contaminated soil environments. Their overall environmental impact is positive by improving soil quality and assisting in natural detoxification.
Managing Large Populations
When roly poly populations begin to damage tender garden plants, simple cultural controls are effective for management. Since they require high moisture levels to survive, reducing dampness is the most direct approach. This involves watering gardens in the morning so the soil surface dries out by evening and ensuring good drainage.
Removing excessive organic debris, such as thick layers of mulch, leaf piles, and old plant matter, eliminates their primary food source and shelter. For localized control, simple traps can be used, such as placing a hollowed-out potato half or a piece of melon rind cut-side down in the garden. The roly polys will congregate beneath the trap overnight and can be collected and relocated the following morning. Indoors, sealing foundation cracks and using dehumidifiers to dry out moist areas will prevent entry.