Pill bugs, also known as roly-polies or woodlice, are common inhabitants of garden and compost environments. These creatures are terrestrial crustaceans, distant relatives of shrimp and crabs, and are the only crustaceans to have fully adapted to life on land. Their presence in a compost pile often leads to questions about their role, but these segmented decomposers are largely beneficial to the composting process. Understanding their functions and preferred conditions is key to leveraging their natural abilities for producing nutrient-rich compost.
What Pill Bugs Consume
Pill bugs are classified as detritivores, meaning their diet consists primarily of detritus, which is dead and decaying organic matter. In a compost setting, their preferred food sources include rotting leaves, wood fibers, and other plant debris that has already begun to break down. They actively seek out and consume fungal growth and aged plant material, which helps to manage the microbial community within the pile.
Their feeding habits are beneficial because they target materials that take longer to decompose, such as cellulose-rich items like cardboard and bark. They also have a high tolerance for ammonia, which they release as a gas rather than through urination, an adaptation for managing nitrogen waste. This focus on decaying matter means they do not pose a threat to fresh, living plant material unless the compost is lacking moisture or proper food sources.
Their Specific Role in Decomposition
Pill bugs function as secondary decomposers, working alongside bacteria and fungi to accelerate the conversion of organic waste into finished compost. Their most important contribution is the physical breakdown of larger pieces of material, often called shredding. By chewing and ingesting coarse organic matter, they significantly reduce the particle size, which increases the surface area available for microbial action.
Their digestive process enhances nutrient cycling within the compost ecosystem. After consuming detritus, pill bugs excrete nitrogen-rich castings (feces). This nutrient-dense waste is more readily available to other microbes and, eventually, to plants when the compost is used. This process helps to unlock and recirculate nutrients bound up in the raw organic matter.
The constant movement of pill bugs through the compost pile provides a helpful degree of aeration. As they tunnel and navigate the material in search of food and moisture, they introduce small pockets of air. This is advantageous for aerobic bacteria that thrive on oxygen and are responsible for high rates of decomposition. Their presence is a reliable indicator of a cool, moist, and biologically active composting environment.
Encouraging or Controlling Their Numbers
Since pill bugs are beneficial decomposers, composters often want to maintain a healthy population. To encourage their presence, ensure the pile has a supply of woody debris and organic matter like leaves, which are their preferred food. Maintaining a consistent moisture level, similar to a wrung-out sponge, is also important, as these land-dwelling crustaceans require humidity to survive because they breathe through gill-like structures.
A sudden increase in the pill bug population can serve as a warning sign about the condition of the compost pile. High numbers indicate that the pile is too cool or overly wet, favoring their survival over the heat-loving bacteria that drive fast composting. To control a dense population, turn the pile more frequently. This introduces air and raises the internal temperature, causing them to retreat to the cooler edges.
If a dense population migrates to nearby living garden seedlings, adjusting the moisture level downward is a common management technique. If the compost is too dry, pill bugs may seek moisture in living roots or tender plant tissue. Conversely, if the pile becomes too wet, they risk drowning, which naturally regulates their numbers without chemical intervention.