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pillbug

Armadillidium vulgare

What do they look like?

Common pillbugs are oval shaped and somewhat flattened. They have three sections to their body: the head, the middle thorax (pereon), and the end abdomen (pleon). On their head, they have eyes and antennae. In the middle pereon, they have seven overlapping plates. On each of these plates is a pair of legs. Adults are about 10 mm long and 5 mm wide. Juveniles are between 5 to 7 mm long. Most pillbugs are gray in color, with the soft underside of the body a lighter color. Some have yellow, red, or brownish sports. Some pillbugs are infected with a virus that turns them blue or purple. ("Isopoda (Pillbugs, Slaters, and Woodlice)", 2003; Beauché and Richard, 2013; Bousfield and Conlan, 2013; Csonka, et al., 2013; Hasegawai, et al., 1999; Hild, et al., 2008; Karasawa, et al., 2012; Moriyama, 2004; Robinson, et al., 2011)

  • Sexual Dimorphism
  • sexes alike
  • Range mass
    0.060 to 0.116 g
    0.00 to 0.00 oz
  • Range length
    0.7 to 18 mm
    0.03 to 0.71 in
  • Average length
    10 mm
    0.39 in

Where do they live?

Armadillidium vulgare, the common pillbug, is originally from the Mediterranean. It has been brought by people to almost all other areas of the world. It is most common in temperate climates. Common pillbugs, also called roly polies, are found throughout the United States, as well as Madagascar, Australia, South Africa, India, Japan, France, Canada, the Czech Republic, and western Romania, among many other places. ("Isopoda (Pillbugs, Slaters, and Woodlice)", 2003; Beauché and Richard, 2013; Ferenţi, et al., 2013; Giraud, et al., 2013; Karasawa, et al., 2012; Moriyama and Migita, 2004; Saska, 2008; Wright and O'Donnell, 2010)

What kind of habitat do they need?

Common pillbugs can be found in forests, fields, gardens, and other suburban and urban areas. They live in areas that are moist, with temperatures that are not too hot or cold, and with little light. They can usually be found under rocks or logs, or burrowed in the soil. ("Isopoda (Pillbugs, Slaters, and Woodlice)", 2003; Beauché and Richard, 2013; Dias, et al., 2012; Ferenţi, et al., 2013; Karasawa, et al., 2012; Moriyama and Migita, 2004; Robinson, et al., 2011; Saska, 2008; Wright and O'Donnell, 2010)

  • Range depth
    .25 (high) m
    0.82 (high) ft

How do they grow?

Pillbugs begin life as eggs. The eggs contain yolk that the young develop on, and the eggs stay inside the female parent in a pouch called the marsupium. While still inside the mother, the eggs hatch into a juvenile stage called a manca. After 3 or 4 days, the mancas crawl out from the marsupium. After they shed their skin several times, they become adults. They continue to shed their skin throughout their lives, in a process that takes about a month. (Beauché and Richard, 2013; Bousfield, et al., 2013; Hild, et al., 2008; Wright and O'Donnell, 2010)

How do they reproduce?

Mating takes place in the spring. Pairs may form a few days before the female is ready to mate. When the female is ready, the male climbs onto the back of the female, and transfers sperm to the female. This can last a few seconds. Both males and females can mate many times in their lives. Female pillbugs can store sperm in their bodies from multiple males. Right after mating, females will not immediately mate again and will reject any potential males until they are ready again. ("Isopoda (Pillbugs, Slaters, and Woodlice)", 2003; Beauché and Richard, 2013; Bousfield and Conlan, 2013; Ferenţi, et al., 2013; Wright and O'Donnell, 2010; Ziegler and Suzuki, 2011)

Common pillbugs can produce offspring up to three times in a year. After mating, eggs remain in a fluid-filled pouch in the female called the marsupium for 2 to 3 months. The eggs hatch inside the female, producing mancas. The mancas stay inside the female for another 3 to 4 days before they emerge. After they undergo a few molts, they are considered independent from their mother. ("Isopoda (Pillbugs, Slaters, and Woodlice)", 2003; Beauché and Richard, 2013)

  • How often does reproduction occur?
    Armadillidium vulgare populations breed once annually in the northern hemisphere and two to three times a year in the southern hemisphere.
  • Breeding season
    The breeding season usually lasts from late spring to early summer. The hatching season generally ends in early fall to late winter.
  • Range number of offspring
    6 to 300
  • Average number of offspring
    100
  • Range gestation period
    8 to 12 weeks
  • Average age at sexual or reproductive maturity (female)
    1 years
  • Average age at sexual or reproductive maturity (male)
    1 years

After mating, male pillbugs leave and go on to mate with other pillbugs, and do not provide any parental care. Females do provide parental care though, as the eggs stay inside the female for several months, before hatching inside her and staying there another couple of days. After the mancas leave the mother, they often stay close to their mother's burrow. They either separate from their mother and live in another tunnel, or they stay with the mother. If they stay, the mother will often protect them within her tunnel until they have developed more. ("Isopoda (Pillbugs, Slaters, and Woodlice)", 2003; Bousfield and Conlan, 2013; Robinson, et al., 2011)

How long do they live?

Most pillbugs live about a year and a half, though some individuals can live up to a few years. (Chevalier, et al., 2011; Le Clec’h, et al., 2013)

  • Range lifespan
    Status: wild
    2 (high) years
  • Average lifespan
    Status: wild
    1.5 years
  • Range lifespan
    Status: captivity
    1.5 (low) years

How do they behave?

One of the most notable behaviors of pillbugs is they way that they roll up into a ball. This is called conglobation. Rolling into a ball is why many people call them 'roly-polies'. When pillbugs are threatened or bothered, they roll into a ball, likely to protect their soft inner body. Rolling into a ball could also limit water loss. Preventing water loss is important for pillbugs. In drier environments, they spend more time taking shelter, rather than feeding or other activities. They are also more active at night when it is cooler. Often they will gather in groups. When moving, they alternate between gradual right and left turns so that they end up moving straight forward. ("Isopoda (Pillbugs, Slaters, and Woodlice)", 2003; Dias, et al., 2012; Moriyama and Migita, 2004; Moriyama, 2004; Robinson, et al., 2011; Saska, 2008; Wright and O'Donnell, 2010; Řezáč and Pekár, 2007)

How do they communicate with each other?

Pillbugs have the senses of sight, smell, and touch. They have eyes that can detect light, but have poor vision otherwise. They can use their sense of smell to find food and identify mates and other pillbugs. They have hairs called setae on their antennae and mouthparts that are used for touch, and can detect objects that they brush against. They can also detect chemicals with their antennae. They produce a chemical called an aggregate pheromone, which other pillbugs can detect. They often mark their trails with this pheromone, which lets pillbugs find each other by following these markings. It may also be involved in mating. The presence of this pheromone also shows other pillbugs that this habitat is desirable, as other pillbugs are clearly able to survive there. (Beauché and Richard, 2013; Bousfield and Conlan, 2013; Moriyama, 2004; Robinson, et al., 2011)

What do they eat?

Common pillbugs are primarily detritovores, eating decomposing leaves and other decaying matter. They will also feed on small pieces of garden roots such as carrots, as well as fruit, and other plants. They also feed on their own feces, which allows them to get nutrients that they could not process during the first digestion. When these food sources are not present, they will eat seeds. Larger pillbugs will even cannibalize smaller pillbugs of the same or different species, especially if the other pillbug is injured. ("Isopoda (Pillbugs, Slaters, and Woodlice)", 2003; Beauché and Richard, 2013; Le Clec’h, et al., 2013; Moriyama and Migita, 2004; Robinson, et al., 2011; Saska, 2008; Řezáč and Pekár, 2007)

  • Animal Foods
  • terrestrial non-insect arthropods
  • Plant Foods
  • leaves
  • roots and tubers
  • seeds, grains, and nuts
  • fruit

What eats them and how do they avoid being eaten?

Common pillbugs have strong defenses against predators. Their body plates are strong, and by rolling into a ball they make it difficult for predators to get to their soft body parts. They have glands that produce unpleasant secretions, which repel predators. Their gray color also acts as camouflage against rocks or wood. Most smaller predators cannot get past these defenses, though there are some tropical ants of the genus Leptogenys that have long pinchers which can pry apart balled-up pillbugs. Spider species of the genus Dysdera are known predators of pillbugs, as well as birds, such as the Common Starling. ("Isopoda (Pillbugs, Slaters, and Woodlice)", 2003; Řezáč and Pekár, 2007)

What roles do they have in the ecosystem?

Common pillbugs feed on decomposing plant matter. They also feed on seeds and feces. They recycle nutrients back into the ecosystem by eating and digesting these things. They can also cause problems for plants by feeding on seeds, preventing them from growing. They are prey for birds, spiders, and ants. Pillbugs can be infected with two kinds of bacteria, Photorhabdus luminescens and Wolbachia. Wolbachia can actually turn all offspring into females. Pillbugs can also be infected by Iridovirus IIV-31 (invertebrate iridescent virus 31), which can turn pillbugs blue or purple, and can shorten their lifespan. They can also be hosts to a parasitic worm, Plagiorhynchus cylindraceus. The worm lives inside the pillbug's digestive system, can cause females to be sterile, and causes changes in their behavior. Infected pillbugs will move out into open areas where birds can more easily prey on them, and then the worm can infect the bird once it has been eaten with the pillbug. ("Acanthocephala (Thorny Headed Worms)", 2003; "Isopoda (Pillbugs, Slaters, and Woodlice)", 2003; Chevalier, et al., 2011; Giraud, et al., 2013; Karasawa, et al., 2012; Le Clec’h, et al., 2013; Saska, 2008; Sicard, et al., 2014; Verne, et al., 2012)

Commensal or parasitic species (or larger taxonomic groups) that use this species as a host
  • nematodes, Nematoda
  • Wolbachia sp.
  • acanthocephalan worm, Plagiorhynchus cylindraceus

Do they cause problems?

Large numbers of pillbugs in gardens or greenhouses may eat and damage young plants, but this is rare and not a big threat. ("Isopoda (Pillbugs, Slaters, and Woodlice)", 2003)

  • Ways that these animals might be a problem for humans
  • crop pest

How do they interact with us?

In central Europe, common pillbugs feed on the seeds of agricultural weeds. This prevents the weeds from growing and competing with crops, allowing for more crops to successfully grow. They are also used in research, as they can easily be kept in very large numbers with little maintenance. They also help to breakdown decomposing plant matter in forests and in gardens, as this is their main source of food. This also releases nutrients back into the soil and ecosystem. Their activity improves the quality of soil, which can be helpful for farmers and gardeners. (Beauché and Richard, 2013; Bousfield and Conlan, 2013; Dias, et al., 2012; Saska, 2008)

  • Ways that people benefit from these animals:
  • research and education
  • controls pest population

Are they endangered?

Common pillbugs are not an endangered species. (Giraud, et al., 2013)

Some more information...

Common names of Armadillidium vulgare include common pill woodlouse, roly poly, and German 'Kugelassel'. The genus was once Armadillo, named after the mammal armadillo, which also rolls into a ball like these pillbugs do. ("Isopoda (Pillbugs, Slaters, and Woodlice)", 2003; Bousfield and Conlan, 2013)

Contributors

Asa Holland (author), Sierra College, Jennifer Skillen (editor), Sierra College, Angela Miner (editor), Animal Diversity Web Staff.

References

2003. Acanthocephala (Thorny Headed Worms). Pp. 316-317 in M Hutchins, A Evans, J Jackson, D Kleiman, J Murphy, D Thoney, eds. Grzimek's Animal Life Encyclopedia, Vol. 1, Second Edition. Farmington Hills, MI: The Gale Group, Inc. Accessed November 27, 2013 at http://www.encyclopedia.com/article-1G2-3406700045/acanthocephala-thorny-headed-worms.html.

2003. Isopoda (Pillbugs, Slaters, and Woodlice). Pp. 249-255 in M Hutchins, A Evans, J Jackson, D Kleiman, J Murphy, D Thoney, eds. Grzimek's Animal Life Encyclopedia, Vol. 1, Second Edition. Farmington Hills, MI: The Gale Group, Inc. Accessed November 26, 2013 at http://www.encyclopedia.com/article-1G2-3406700118/isopoda-pillbugs-slaters-and.html.

Beauché, F., F. Richard. 2013. The Best Timing of Mate Search in Armadillidium vulgare (Isopoda, Oniscidea). PLoS ONE, 8/3: 1-9. Accessed October 24, 2013 at http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0057737.

Bousfield, E., K. Conlan. 2013. Malacostracan. W Doniger, R Fishman, B Friedman, L Gelb, D Gelernter, M Gell-Mann, V Gregorian, eds. Encyclopaedia Britannica, 15th Edition. Chicago, Illinois: Encyclopædia Britannica, Inc. Accessed November 28, 2013 at http://www.britannica.com/EBchecked/topic/359445/malacostracan.

Bousfield, E., K. Conlan, I. Gordon, J. Green, W. Newman. 2013. Crustacean. W Doniger, R Fishman, B Friedman, L Gelb, D Gelernter, V Gregorian, eds. Encyclopaedia Britannica, 15th Edition. Chicago, Illinois: Encyclopædia Britannica, Inc. Accessed November 29, 2013 at http://www.britannica.com/EBchecked/topic/144848/crustacean.

Chevalier, F., J. Herbinière-Gaboreau, J. Bertaux, M. Raimond, F. Morel, D. Bouchon, P. Grève, C. Braquart-Varnier. 2011. The Immune Cellular Effectors of Terrestrial Isopod Armadillidium vulgare: Meeting with Their Invaders, Wolbachia. PLoS ONE, 6/4: 1-11. Accessed October 24, 2013 at http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0018531.

Csonka, D., K. Halasy, P. Szabó, P. Mrak, J. Štrus, E. Hornung. 2013. Eco-morphological Studies on Pleopodal Lungs and Cuticle in Armadillidium Species (Crustacea, Isopoda, Oniscidea). Arthropod Structure and Development, 42/3: 229-235. Accessed November 27, 2013 at http://www.sciencedirect.com/science/article/pii/S1467803913000042.

Dias, N., M. Hassall, T. Waite. 2012. The Influence of Microclimate on Foraging and Sheltering Behaviours of Terrestrial Isopods: Implications for Soil Carbon Dynamics Under Climate Change. Pedobiologia, 55/3: 137-144. Accessed November 27, 2013 at http://www.sciencedirect.com/science/article/pii/S0031405611001077.

Ferenţi, S., D. Cupşa, A. Cicort-Lucaciu, S. Covaciu-Marcov. 2013. Winter Activity of Terrestrial Isopods From Thermal Habitats in Western Romania. Archives of Biological Sciences, 65/2: 795-800. Accessed October 27, 2013 at http://journaldatabase.org/articles/winter_activity_terrestrial_isopods.html.

Giraud, I., V. Valette, N. Bech, F. Grandjean, R. Cordaux. 2013. Isolation and Characterization of Microsatellite Loci for the Isopod Crustacean Armadillidium vulgare and Transferability in Terrestrial Isopods. PLoS ONE, 8/10: e76639. Accessed October 27, 2013 at http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0076639.

Hasegawai, Y., S. Negishi, J. Naito, R. Ikedas, H. Hasegawa, Y. Nagamura. 1999. Ommochrome Deficiency in an Albino Strain of a Terrestrial Isopod, Armadillidium vulgare. Pigment Cell Research, 12/4: 275-282. Accessed November 26, 2013 at http://www.ncbi.nlm.nih.gov/pubmed/10454296.

Hild, S., O. Marti, A. Ziegler. 2008. Spatial Distribution of Calcite and Amorphous Calcium Carbonate in the Cuticle of the Terrestrial Crustaceans Porcellio scaber and Armadillidium vulgare. Journal of Structural Biology, 163/1: 100-108. Accessed November 27, 2013 at http://www.sciencedirect.com/science/article/pii/S1047847708001214.

Karasawa, S., J. Takatsuka, J. Kato. 2012. Report on Iridovirus Nv-31 (Iridoviridae, Iridovirus) Infecting Terrestrial Isopods (Isopoda, Oniscidea) in Japan. Crustaceana, 85/10: 1269-1278. Accessed October 24, 2013 at http://booksandjournals.brillonline.com/content/journals/10.1163/15685403-00003116.

Le Clec’h, W., F. Chevalier, L. Genty, J. Bertaux, D. Bouchon, M. Sicard. 2013. Cannibalism and Predation as Paths for Horizontal Passage of Wolbachia between Terrestrial Isopods. PLoS ONE, 8/4: e60232. Accessed October 27, 2013 at http://www.plosone.org/article/info:doi/10.1371/journal.pone.0060232.

Moriyama, T. 2004. Problem Solving and Autonomous Behavior in Pill Bugs (Armadillidium vulgare). Ecological Psychology, 16/4: 287-302. Accessed October 24, 2013 at http://www.tandfonline.com/doi/abs/10.1207/s15326969eco1604_2#.UpY1BcRDvh4.

Moriyama, T., M. Migita. 2004. Decision-making and Anticipation in Pill Bugs (Armadillidium vulgare). AIP Conference Precedings, 718/1: 459-464. Accessed October 24, 2013 at http://scitation.aip.org/content/aip/proceeding/aipcp/10.1063/1.1787349.

Robinson, B., K. Larsen, H. Kerr. 2011. Natal Experience and Conspecifics Influence the Settling Behaviour of the Juvenile Terrestrial Isopod Armadillidium vulgare. Canadian Journal of Zoology, 89/8: 661-667. Accessed October 27, 2013 at http://www.nrcresearchpress.com/doi/abs/10.1139/z11-030#.UpY2RcRDvh4.

Saska, P. 2008. Granivory in Terrestrial Isopods. Ecological Entomology, 33/6: 742-747. Accessed October 24, 2013 at http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2311.2008.01026.x/abstract.

Sicard, M., M. Raimond, S. Gaudriault, A. Lanois, S. Pagès, C. Debenest, C. Braquart-Varnier, A. Givaudan. 2014. Putative Toxins from the Entomopathogenic Bacterium Photorhabdus luminescens Kill Armadillidium vulgare (Terrestrial Isopod). Biological Control, 69: 40-44. Accessed November 27, 2013 at http://www.sciencedirect.com/science/article/pii/S1049964413002417#f0005.

Verne, S., M. Johnson, D. Bouchon, F. Grandjean. 2012. Effects of Parasitic Sex-ratio Distorters on Host Genetic Structure in the Armadillidium vulgare-Wolbachia Association. Journal of Evolutionary Biology, 25/2: 264-276. Accessed October 24, 2013 at http://www.ncbi.nlm.nih.gov/pubmed/22188300.

Wright, J., M. O'Donnell. 2010. In Vivo Ion Fluxes Across the Eggs of Armadillidium vulgare (Oniscidea: Isopoda): The Role of the Dorsal Organ. Physiological & Biochemical Zoology, 83/4: 587-596. Accessed October 24, 2013 at http://www.ncbi.nlm.nih.gov/pubmed/20465420.

Ziegler, A., S. Suzuki. 2011. Sperm Storage, Sperm Translocation and Genitalia Formation in Females of the Terrestrial Isopod Armadillidium vulgare (Crustacea, Peracarida, Isopoda). Arthropod Structure and Development, 40/1: 64-76. Accessed November 27, 2013 at http://www.sciencedirect.com/science/article/pii/S1467803910000514.

Řezáč, M., S. Pekár. 2007. Evidence for Woodlice-specialization in Dysdera Spiders: Behavioural Versus Developmental Approaches. Physiological Entomology, 32/4: 367-371. Accessed October 24, 2013 at http://onlinelibrary.wiley.com/doi/10.1111/j.1365-3032.2007.00588.x/abstract.

 
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