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Pill bug
Pill bug
Pill bug in its defensive posture
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Subphylum: Crustacea
Class: Malacostraca
Order: Isopoda
Suborder: Oniscidea
Family: Armadillidiidae
Brandt, 1833

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.

Pill bugs are not insects, but are crustaceans. Crustaceans are animals with hard shells made from many pieces for protection.

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.

Pill bugs look like gray pills. The pill bug's abdomen has seven segments. Pill bugs have flat bodies. The pill bug has three basic body parts called the head, thorax, and abdomen, moce and they can be many sizes.

The head has eyes (simple and compound) and a mouth. Pill bugs have two sets of antennae. One of the sets is visible to see. The thorax holds the legs. The abdomen holds the exopods of uropods and is attached to some crustaceans' abdomens. Pillbugs eat rotten plants, rotten animals, old garbage, and even bits of food in animal dung. Pill bugs do not breathe through lungs; they have gills. Because of this, they need to be in a damp place or they will die. They also prefer dark rocks or any other dark place to stay that is dark. They are more active at night and early morning because of the darkness.

Pill bugs have the typical lifespan of an Isopod, living two years average and five years maximum.

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.

Classification

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
  • Armadillidium
  • Ballodillium
  • Cristarmadillidium
  • Cyphodillidium
  • Echinarmadillidium
  • Eleoniscus
  • Eluma
  • Paraschizidium
  • Paxodillidium
  • Platanosphaera
  • Schizidium
  • Trichodillidium
  • Troglarmadillidium
  • Typhlarmadillidium


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