Woodlice, often recognized by the names roly-polies or pill bugs, are common inhabitants of gardens and woodlands. These small terrestrial organisms belong to the suborder Oniscidea, making them crustaceans, related more closely to crabs and shrimp. They are one of the few groups of crustaceans to have successfully adapted to a life entirely on land. Woodlice play a significant role in terrestrial ecosystems as macrodetritivores, consuming decaying matter to facilitate nutrient cycling.
The Foundational Diet: Detritus and Decay
The primary diet of woodlice consists of detritus, which is dead and decaying organic material. Their feeding habits center on fallen leaves, compost, and rotting wood, making them integral to decomposition. By consuming this material, woodlice fragment larger pieces of organic matter, increasing the surface area for microbial breakdown. This process benefits soil health by rapidly releasing nutrients back into the earth for plant growth.
Their digestive systems possess specialized adaptations that allow them to break down tough plant compounds like cellulose and lignin. Fresh plant material is generally avoided, as living tissues are more difficult to process than pre-softened, decaying matter. Woodlice are essentially consuming the micro-organisms, such as bacteria and fungi, that are already working to break down the detritus. They are secondary consumers of the decay process, relying on microbial activity to condition their food source.
The presence of fungi enhances the nutritional value of their meals. While woodlice prefer decaying matter, they will sometimes nibble on tender plant parts or seedlings if preferred food sources are scarce. Their continuous feeding activity contributes to the enrichment and aeration of the soil. They are most active in scavenging at night or during moist conditions, which helps them avoid dehydration while foraging.
Specific Nutritional Needs and Preferences
Beyond the general consumption of detritus, woodlice actively seek out specific nutrients for their growth and maintenance. The most important specialized need is a steady supply of calcium, used to construct their rigid exoskeleton. Like all crustaceans, woodlice must periodically shed their outer shell to grow. This process, called molting, requires a large and immediate influx of calcium.
The molting process is unique because the woodlouse sheds its exoskeleton in two parts, with the rear half coming off a few days before the front half. To quickly reclaim the lost mineral, the woodlouse often immediately consumes its shed skin, known as the exuviae. This act allows them to recover the calcium carbonate needed to harden the new exoskeleton. Sources of calcium include crushed eggshells, limestone powder, or cuttlebone.
Woodlice also seek high-protein sources, which are sometimes lacking in simple leaf litter. Fungi are a favored addition to the diet, offering a concentrated source of protein and other nutrients. Opportunistic feeding may occur on dead insects, animal feces, or shed snake skins, all providing protein and mineral content. These specific preferences highlight a foraging strategy aimed at fulfilling cyclical physiological demands.
The Link Between Diet and Environment
The feeding location and food choice of the woodlouse are intrinsically linked to their physiological requirement for moisture. Woodlice are terrestrial crustaceans that breathe using gill-like structures. They lack the waxy cuticle that helps insects retain water, making them highly susceptible to desiccation. Consequently, they must seek out environments with high humidity.
Consequently, their diet must be found in the same damp, dark places that provide shelter, such as under logs, rocks, and thick layers of leaf litter. The detritus they consume is typically damp or saturated, providing dietary water in addition to nutrients. Food quality can sometimes be secondary to the humidity of the location, as survival depends on maintaining water balance.
If the outdoor environment becomes too dry, woodlice may be drawn to human dwellings in search of moisture. They are often found in basements, crawl spaces, or bathrooms, consuming any available organic matter, like damp paper or decaying wood. This movement is a direct consequence of their need to couple their feeding activity with a water-rich microclimate.