The creature commonly known as the roly-poly is a familiar sight in damp, dark places. Unlike garden insects, the roly-poly is actually a terrestrial crustacean, making it a distant relative of shrimp and lobsters. These land-dwelling isopods, also called pill bugs or woodlice, must live in moist environments because they possess gill-like structures that require humidity to function. Their habitat is typically under rocks, logs, and leaf litter.
Primary Diet: Decomposers of the Garden
The roly-poly is classified as a detritivore, meaning its diet consists almost entirely of detritus—dead and decaying organic matter. They consume fallen leaves, rotting wood, soft grasses, and other decomposing plant material, which provides the majority of their energy and moisture.
Their feeding habits perform a beneficial ecological service by acting as nature’s recyclers. By ingesting large quantities of decaying material, they break down coarse matter into smaller fragments. This physical breakdown accelerates decomposition, allowing microorganisms and fungi to finish the job faster. The waste they excrete is nutrient-rich humus, which returns nitrogen, carbon, and other minerals to the soil for living plants to absorb.
Occasional Diet: When They Become Garden Pests
While roly-polies primarily consume dead matter, they occasionally turn their attention to live plants when their preferred food source is scarce. This shift often signals high population density or a lack of sufficient decaying material nearby. When seeking alternative sustenance, they target the softest, most vulnerable plant tissues.
Tender young seedlings are particularly susceptible, as the roly-polies can chew through the delicate stems and soft roots. They also target fruits that rest directly on the soil, such as ripe strawberries, creating holes in the skin to access the moisture and sugars inside. Providing ample decaying wood and leaf litter in a garden is an effective way to redirect their appetite back to their primary food source, minimizing damage to vulnerable crops.
Unique Nutritional Needs
Roly-polies have specific biological requirements that drive unusual feeding behaviors. As terrestrial crustaceans, they must shed their rigid exoskeleton to grow, which demands a high amount of calcium. They obtain this mineral by consuming calcium-rich materials in their environment, such as mineral-rich soil, old snail shells, or powdered limestone.
Another unique practice is coprophagy, the consumption of their own feces, which conserves nutrients. Roly-polies require the mineral copper for their blue, hemocyanin-based blood, but they lose some copper with each defecation. By re-ingesting their waste, they efficiently recycle and reabsorb essential minerals, ensuring the body retains these elements.
Feeding Roly-Polies in Captivity
For roly-polies kept in captivity, the diet is managed by mimicking their natural environment. The bulk of their captive diet should consist of decaying organic material, such as well-rotted hardwood or dried, fallen leaves. This base can be supplemented with various kitchen scraps, including soft vegetable peelings like potato, carrot, and apple skins.
Small amounts of protein, such as fish flakes or commercial animal feed pellets, can be added to ensure sufficient nutrients. Avoid feeding them anything treated with pesticides, as they accumulate heavy metals from their food source. Additionally, avoid highly acidic foods like citrus, and remove any uneaten food quickly to prevent mold growth.