Rolly pollies, also known as pill bugs or woodlice, are common backyard inhabitants that require specific conditions to survive on land. These small creatures are often mistaken for insects, but they are actually terrestrial crustaceans belonging to the order Isopoda. Their survival depends on their specialized biology, essential environmental conditions, and specific nutritional components.
Defining Their Unique Biology
The physical requirements for a rolly polly’s survival are dictated by its classification as a crustacean, which places it in the same group as crabs and shrimp. Unlike true insects, these land-dwelling isopods breathe using specialized gill-like structures, known as pleopodal lungs, located on the underside of their abdomen. This respiratory system is a relic of their aquatic ancestry, and it must remain constantly moist to facilitate oxygen exchange.
This reliance on a moist respiratory organ means the animal is extremely susceptible to desiccation in dry air. If the ambient humidity drops, the gills dry out, and oxygen exchange becomes impossible, leading to death within hours. Their ability to roll into a tight ball, a defense mechanism called conglobation, protects their soft underparts and helps retain internal moisture. They also possess specialized organs called uropods, which allow them to absorb water directly from damp surfaces or humid air.
Essential Environmental Requirements
The biological need for moisture translates directly into a requirement for a high-humidity environment. While they need dampness to breathe, they cannot survive being submerged in standing water and will quickly drown. The ideal habitat provides a balance of moisture in the substrate, such as soil or leaf litter, that is damp but not soaking wet.
To regulate their moisture and temperature, rolly pollies require constant access to dark, protective shelter. They are largely nocturnal, spending the daylight hours concealed beneath objects like decaying logs, rocks, bricks, or thick leaf litter. These hiding places create a microclimate that shields them from direct sunlight, which would rapidly dry out their gills, and from predators.
Rolly pollies also require moderate and stable temperatures because their bodies cannot internally regulate heat. They cannot survive extreme heat or cold, which is why they seek the insulating environment of deep soil or decaying organic matter.
Diet and Nutritional Needs
As detritivores, rolly pollies perform a significant role as decomposers, and their diet consists primarily of decaying organic matter. They consume dead plant material, such as rotting wood, fallen leaves, grass clippings, and compost, which are essential for recycling nutrients back into the soil. They use their mouthparts to scrape and grind this decomposing matter into a pulp for digestion.
Beyond general organic material, these crustaceans have a specific need for calcium to maintain and rebuild their exoskeleton during the molting process. This mineral is often obtained from decaying wood, mineral supplements, or sometimes even through the practice of consuming their own feces, known as coprophagy. While they prefer soft, decaying matter, they will occasionally consume fungi, algae, or soft, live plant seedlings when their preferred food sources are scarce.