Temporal range: Chattian-recent
|An Armadillidium granulatum in various stages of conglobulation, i.e., "rolling up"|
Armadillidiidae is a family of woodlice, a terrestrial crustacean group in the order Isopoda. Unlike members of other woodlice 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 or roly polies. Other common names include slaters, potato bugs, and doodle bugs. The best known species in the family is Armadillidium vulgare, the common pill bug. Pill bugs are native to Europe, wherefrom they were introduced to the Americas.
Ecology and behavior
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 and 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 into 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:
- Alloschizidium Verhoeff, 1919 (13 species)
- Armadillidium Brandt, 1831 (189 species)
- Ballodillium Vandel, 1961 (monotypic)
- Cristarmadillidium Arcangeli, 1936 (4 species)
- Cyphodillidium Verhoeff, 1939 (monotypic)
- Echinarmadillidium Verhoeff, 1901 (3 species)
- Eleoniscus Racovitza, 1907 (monotypic)
- Eluma Budde-Lund, 1885 (3 species)
- Paraschizidium Verhoeff, 1919 (5 species)
- Paxodillidium Schmalfuss, 1985 (monotypic)
- Platanosphaera Strouhal, 1956 (6 species)
- Schizidium Verhoeff, 1901 (26 species)
- Trichodillidium Schmalfuss, 1989 (3 species)
- Troglarmadillidium Verhoeff, 1900 (8 species)
- Trogleluma Vandel, 1946 (2 species)
- Typhlarmadillidium Verhoeff, 1900 (4 species)
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