|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. The roly polies 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.
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 remove many of the toxic metal ions from the soil. 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:
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