Rolly pollies are small, gray, segmented creatures. Their presence indoors is almost always an accidental event stemming from an outdoor population that has grown large due to favorable conditions. The migration happens when the environment immediately surrounding the home’s foundation becomes inhospitable, forcing the creatures to seek temporary refuge indoors. They are not seeking food or permanent shelter inside, but are simply entering through ground-level openings while attempting to escape extreme weather conditions.
Understanding the Pill Bug’s Biology
The creature commonly called a “rolly pollie” is a pill bug (Armadillidium vulgare), which is not an insect but a terrestrial isopod, making it a type of crustacean related to shrimp and lobsters. They are one of the few crustaceans that have fully adapted to life on land, yet they retain a fundamental physiological connection to water. This link is due to their specialized respiratory organs, which are gill-like structures located on their abdominal segments.
These respiratory structures require constant moisture to function, which makes the pill bug highly susceptible to desiccation. Because they lack the waxy cuticle that insects use to prevent water loss, pill bugs must actively seek out dark, damp environments, such as under rocks, leaf litter, and rotting wood, to maintain their body water balance. Their ecological role is that of a detritivore, meaning they function as decomposers by feeding on decaying organic matter.
Why They Seek Shelter Indoors
Pill bugs are sensitive to environmental changes and are typically driven toward homes by fluctuations in moisture levels outdoors. Their indoor appearance is a direct response to two opposing outdoor conditions: extreme dryness and excessive saturation. During periods of drought, the pill bugs’ natural habitats—such as mulch beds and leaf piles—dry out, and the organisms are forced to move away from the desiccation risk near the foundation.
Conversely, heavy rains can saturate the ground, which poses a drowning risk to the organisms. The ground-level perimeter of the home becomes a temporary target for shelter, as the pill bugs search for a stable microclimate. They are not equipped to survive long-term indoors and will quickly dry out and die unless they find a humid spot.
Practical Steps for Exclusion and Prevention
Stopping pill bugs from entering the home requires a dual-pronged approach focusing on physical barriers and environmental control. The first step involves exclusion, which means sealing the tiny gaps and cracks that serve as entry points along the foundation and ground-level access areas. This includes applying caulk to cracks in the foundation, installing tight-fitting door sweeps on all exterior doors, and ensuring ground-level window frames are properly sealed.
The second strategy involves environmental control, which focuses on eliminating the high-moisture habitats that support large outdoor populations near the house. Reducing the local population requires several steps:
- Remove debris like leaf litter, grass clippings, and boards from the area immediately surrounding the foundation.
- Reducing the depth of mulch to no more than two inches and pulling it back from the foundation will create a dry zone that discourages pill bug habitation.
- Addressing water sources by repairing leaky outdoor faucets and ensuring gutters drain water away from the house.
- Storing firewood off the ground and away from the exterior walls.