|Armadillidium vulgare in its defensive posture|
Armadillidiidae is a family of woodlice, a terrestrial crustacean group in the order Isopoda. Unlike members of other woodlouse families, members of this family can roll into a ball, an ability they share with the outwardly similar but unrelated pill millipedes and other animals. It is this ability which gives woodlice in this family their common name of pill bugs or roly polies. The best known species in the family is Armadillidium vulgare, the common pill bug.
Ecology and behaviour
Woodlice in the family Armadillidiidae are able to form their bodies into a ball shape, in a process known as conglobation. This behaviour is shared with pill millipedes (which are often confused with pill bugs), armadillos and cuckoo wasps. It may be triggered by stimuli such as vibrations or pressure, and is a key defence against predation; it may also reduce respiratory water losses.
Relationships with people
Pill-bugs can be considered pests of homes and gardens. They are, however, cherished among children, who enjoy keeping them as pets.  Keeping a pet pill bug requires a very moist habitat with limited light. They can live for about two to three years.
Owners of pet tarantulas sometimes keep pill bugs as cage cleaners in the same habitat. The pill bugs eat faeces, mould, and leftovers. They are sometimes caught and fed to pets such as lizards, but this is not recommended since those animals might become poisoned.
The family Armadillidiidae is differentiated from other woodlouse families by the two-segmented nature of the antennal flagellum, by the form of the uropods, and by the ability to roll into a ball, or conglobate.
Within the family Armadillididae, fifteen genera are currently recognised:
- Gordon Gordh & David H. Headrick (2011). "Common pillbug". A Dictionary of Entomology (2nd ed.). CAB International. p. 343. ISBN 9781845935429.
- Kenn Kaufman & Kimberly Kaufman (2012). Kaufman Field Guide to Nature of New England. Houghton Mifflin Harcourt. p. 364. ISBN 9780618456970.
- "Pill millipede (Glomeris marginata)". ARKive. Retrieved June 21, 2007.
- Edward M. Barrows (2001). Animal behavior desk reference: a dictionary of animal behavior, ecology, and evolution (2nd ed.). CRC Press. p. 142. ISBN 978-0-8493-2005-7.
- Jacob T. Smigel & Allen G. Gibbs (2008). "Conglobation in the pill bug, Armadillidium vulgare, as a water conservation mechanism" (PDF). Journal of Insect Science 8 (44): 1–9. doi:10.1673/031.008.4401. PMID 20233103.
- David V. Alford (2012). "Woodlice". Pests of Ornamental Trees, Shrubs and Flowers (2nd ed.). Manson Publishing. pp. 434–435. ISBN 9781840761627.
- Sheryl Smith-Rogers (October 2009). "Wild Thing: Roly-Poly Pillbugs". TPW Magazine. Retrieved July 10, 2010.
- Stanley A. Schultz & Marguerite J. Schultz (2009). The Tarantula Keeper's Guide: Comprehensive Information on Care, Housing, and Feeding. Barron's Educational Series. pp. 181–183. ISBN 978-0-7641-3885-0.
- Eve Adamson (2005). Adopting a Pet For Dummies. For Dummies. p. 325. ISBN 978-0-7645-9879-1.
- P. J. Hayward & John Stanley Ryland (1995). "Crustaceans". Handbook of the marine fauna of north-west Europe. Oxford University Press. pp. 289–461. ISBN 978-0-19-854055-7.
- Marilyn Schotte (2012). "Armadillidiidae". In M. Schotte, C. B. Boyko, N. L. Bruce, G. C. B. Poore, S. Taiti & G. D. F. Wilson. World Marine, Freshwater and Terrestrial Isopod Crustaceans database. World Register of Marine Species. Retrieved September 26, 2012.