Roly polies, also known by names like pill bugs or woodlice, are familiar inhabitants of backyards and gardens across many regions. These small, segmented creatures are often found scuttling under rocks or logs, and they are particularly known for their distinctive ability to roll into a tight ball when disturbed. Their common presence often leads to a frequent question: are these fascinating little animals actually insects?
Are Roly Polies Insects?
Despite their widespread presence alongside many garden insects, roly polies are not classified as insects. Insects possess distinct characteristics. A true insect body is typically divided into three distinct segments: a head, a thorax, and an abdomen. They also have six legs attached to their thorax, one pair of antennae, and often possess wings in their adult stage.
A roly poly’s anatomy differs significantly from these insect characteristics. Roly polies have more than six legs, typically possessing seven pairs of legs. Their bodies appear to have a more uniform segmentation, lacking the clear three-part division seen in insects. These distinctions confirm roly polies are not insects.
Crustaceans of the Land
Roly polies are, in fact, terrestrial crustaceans, placing them in the same broad group as crabs, lobsters, and shrimp. Specifically, they belong to the order Isopoda, making them isopods. This classification highlights their evolutionary ties to marine life, even though they have successfully adapted to living entirely on land.
Their crustacean lineage is evident in several features, including their hard, segmented exoskeleton that provides protection. Unlike most land-dwelling arthropods, roly polies breathe using gill-like structures, which require a consistently moist environment to function properly. This reliance on moisture links them directly to their aquatic ancestors and explains why they thrive in damp habitats. Their seven pairs of legs are also a characteristic trait shared with many other crustaceans.
Roly Poly Habits and Homes
Roly polies prefer to live in environments that offer consistent moisture and darkness. They are commonly found under rocks, logs, leaf litter, and decaying wood, where the humidity levels remain high and they are protected from direct sunlight and predators.
These creatures are detritivores, meaning they primarily feed on decaying organic matter such as dead leaves, rotting wood, and other plant debris. By consuming this decomposing material, roly polies act as decomposers, breaking down organic matter and returning nutrients to the soil. When threatened, roly polies employ conglobation, rolling into a tight, armored ball to protect their softer underside from predators.