Roly-polies, often called pill bugs or woodlice, are common decomposers found in gardens and moist environments worldwide. Despite their insect-like appearance, these creatures are terrestrial crustaceans, making them related to shrimp and lobsters. They are known for their defense mechanism of rolling into a tight ball, a behavior known as conglobation. Understanding the visual characteristics of their waste, or frass, is the clearest way to confirm their presence.
Visual Characteristics of Roly-Poly Frass
The droppings produced by a roly-poly are extremely small, typically measuring only the size of a pin-prick or a coarse grain of sand. This miniature size makes the individual pellets difficult to notice unless examined closely against a contrasting surface. The shape of the frass is generally spherical or perfectly round, sometimes appearing slightly oval.
The color of the frass is determined by the roly-poly’s diet, which consists mainly of decaying organic matter such as rotting leaves and wood. This results in droppings that are consistently dark brown to black. When these tiny pellets accumulate, they often look like a fine dusting of dirt or ground coffee.
A defining characteristic of roly-poly waste is its texture and dryness, a direct result of their unique biology. Unlike many other animals, roly-polies do not excrete liquid urine to rid their bodies of ammonia. Instead, they release ammonia as a gas through their exoskeleton, which helps them conserve water. This results in very dry, brittle fecal matter that easily crumbles.
Identification Context: Where to Find the Droppings
Roly-polies are highly dependent on moisture to breathe, utilizing gill-like structures. Therefore, their frass is almost exclusively found in damp, dark, and sheltered locations. Outdoors, the droppings are scattered throughout areas of high humidity and organic debris, such as under logs, rocks, garden pots, or mulch. They are often found along the foundation of buildings where moisture is retained.
If droppings are found indoors, it suggests roly-polies entered the home searching for moisture during dry conditions. The frass will be concentrated in areas with high humidity, such as damp basements, crawl spaces, and near leaky plumbing. The droppings are scattered randomly across surfaces rather than deposited in large, concentrated piles, making them easy to overlook unless the population is large.
Distinguishing Roly-Poly Waste from Other Small Invertebrates
Differentiating roly-poly frass from the droppings of other common household pests requires attention to the specific shape and size of the pellets. Drywood termite frass is often mistaken for roly-poly droppings, but termite pellets are characteristically six-sided (hexagonal) with concave sides. They are often found in concentrated mounds beneath small “kick-out” holes in wood.
Rodent droppings, such as those from mice, are significantly larger than roly-poly frass, appearing closer to the size of a grain of rice with a cylindrical shape and pointed ends. Roly-poly droppings are microscopic in comparison, being perfectly round and sand-sized. Some insect droppings, like those from certain cockroaches, can look like black pepper or coffee grounds, but they are often cylindrical and may possess small ridges, unlike the smooth, spherical roly-poly pellets.