Pillbugs

Definition

Terrestrial isopod crustaceans in the family Armadillidiidae, characterized by the ability to conglobate—roll into a tight defensive ball when disturbed. This convergent trait resembles that of unrelated pill millipedes (Glomerida) but distinguishes pillbugs from most other woodlice families. Common in leaf litter, soil, and decaying wood; important decomposers in terrestrial ecosystems.

Etymology

From 'pill' (small rounded object or tablet) + 'bug' (general term for small terrestrial arthropod), referring to the rolled defensive posture.

Example

Armadillidium vulgare, the common pillbug, was introduced to North America in the early 19th century and now occurs widely in gardens and compost heaps, where it fragments decaying plant material.

Synonyms

• rolly pollies
• potato bugs
• doodle bugs
• slaters
• curly bugs

Related Terms

• Woodlice
• isopods
• conglobation
• pill millipedes
• detritivores
• Armadillidiidae

Usage Notes

Though called 'bugs,' pillbugs are crustaceans (Isopoda), not insects (Hemiptera). The term specifically refers to conglobating members of Armadillidiidae; non-rolling woodlice in families like Porcellionidae are not pillbugs. 'Rolly pollies' and regional variants are common names without taxonomic standing. Contrast with pill millipedes (Diplopoda: Glomerida), which independently evolved similar rolling behavior.