|Armadillidium vulgare walking (above) and in defensive posture (below)|
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. This ability gives woodlice in this family their common names of pill bugs, roly polies, and doodle bugs. The best known species in the family is Armadillidium vulgare, the common pill bug. Pill bugs are not native to the Americas, but instead were introduced from Europe.
Ecology and behaviour
Pill bugs 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 defense against predation; it may also reduce respiratory water losses.
The diet of pill bugs is largely made up of decaying or decomposed plant matter such as leaves, and to a lesser extent, wood fibers. Pill bugs will also eat living plants, especially in wet conditions, sometimes consuming leaves, stems, shoots, roots, tubers, and fruits. Pill bugs can be serious pests in certain agricultural systems, particularly in areas that are prone to heavy rains and flood conditions. Pill bugs will feed on numerous crop plants including corn, beans, squash, peas, melon, chard, beet, cucumber, potato, spinach, lettuce, and strawberry, with potential for significant yield loss in strawberry in particular. Some species of pill bugs are known to eat decaying animal flesh or feces. They will also eat shed snakeskin and dead bugs, if necessary.
Pill bugs contribute to their ecosystem as decomposers. They are capable of taking in heavy metals such as copper, zinc, lead and cadmium and crystallize these out as spherical deposits in the midgut. In this way, they temporarily remove many of the toxic metal ions from the soil although the toxic metals are returned to the soil when they die. They also provide a food source for birds, toads, spiders, wasps, and centipedes.
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.
Within the family Armadillidiidae, 15 genera are currently recognized:
- 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. Archived from the original on 2006-06-17. Retrieved June 21, 2007.
- Edward M. Barr (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". Journal of Insect Science. 8 (44): 1–9. doi:10.1673/031.008.4401. PMC 3127403. PMID 20233103.
- "What Do Pill Bugs Eat?". Orkin.com. Retrieved 8 May 2018.
- Hopkin, S.P.; Hardisty, G.N.; Martin, M.H. (January 1986). "The woodlouse Porcellio scaber as a 'biological indicator' of zinc, cadmium, lead and copper pollution". Environmental Pollution Series B, Chemical and Physical. 11 (4): 271–290. doi:10.1016/0143-148x(86)90045-5. ISSN 0143-148X.
- 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). Schotte M, Boyko CB, Bruce NL, Poore GC, Taiti S, Wilson GD, eds. "Armadillidiidae". World Marine, Freshwater and Terrestrial Isopod Crustaceans database. World Register of Marine Species. Retrieved September 26, 2012.