Porcellio scaber

Distinguished from smooth woodlouse species (e.g., Porcellio laevis) by the rough, tuberculate dorsal surface. Separated from 'roller' woodlice such as Armadillidium spp. by its inability to conglobate; when disturbed, P. scaber adopts tonic immobility or flees rather than rolling into a ball. Distinguished from Oniscus asellus by less dependence on high humidity and preference for drier microhabitats. The combination of rough exoskeleton, oval non-conglobating body form, and grey coloration with paler ventral surface is diagnostic in most of its range.

Occupies a wide variety of damp habitats including forests, gardens, urban green spaces, and coastal areas. Seeks small, narrow spaces to minimize water loss due to permeable exoskeleton lacking waxy cuticle. Avoids bright light to prevent desiccation. Uses loose bark of dead or dying trees and flat-lying compact objects as day shelters. Less dependent on high humidity than Oniscus asellus, allowing occupation of somewhat drier microhabitats. Requires moisture for respiration and proper ecdysis.

Native to Central and Western Europe. Introduced and established in North America, South Africa, Australia (where it is the most common woodlouse), and sub-Antarctic Marion Island. Widespread across the United Kingdom as one of the most common woodlice. Distribution expanded globally through human activity.

Detritivore feeding primarily on decaying leaf litter and rotting plant matter. Consumes bacteria and fungi associated with decomposition rather than living plant tissue. Uses sensitive olfactory receptors to detect microbial activity and locate food. Has been observed engaging in coprophagy (consumption of fecal material).

Females carry 25–90 fertilized eggs in a fluid-filled ventral brood pouch (marsupium) for approximately 40–50 days until hatching. Young reach reproductive maturity after approximately 3 months. Adult life expectancy approximately 2 years. Size categories correlate with age: small individuals <7 mm, medium 7–12 mm, large >12 mm. Ecdysis (molting) occurs periodically; new epicuticle forms at least 21 hours before moulting, with new chitinous cuticle differentiating into exocuticle and endocuticle approximately 5 hours after moulting.

Exhibits nocturnal activity patterns correlated with air humidity regulation. Activity serves to balance water uptake and transpiration: animals accumulate water in moist shelters, then move to drier areas to transpire excess, with activity periods lasting approximately one hour for most individuals. Shows hygrokinesis (high activity in dry air, motionless in saturated air) and hygrophobotactic behavior (movement toward moist air). Demonstrates turn alternation during klinokinesis, with alternating left-right turns averaging to straight-line movement for efficient escape. When threatened, adopts tonic immobility (death feigning/thanatosis) with body contraction, legs folded ventrally, and antennae folded or extended backwards; duration of immobility varies individually and consistently, indicating personality traits ('bold' vs. 'shy' individuals). Main defenses are escape running, sticking to surfaces, and chemical secretions rather than tonic immobility. Shows strong thigmotaxis (preference for contact with surfaces). Lives in large aggregations. Habituation to environments occurs within approximately 10 minutes, reducing sensitivity to repeated stimuli.

Decomposer contributing to nutrient cycling through consumption of decaying plant matter and associated microorganisms. Prey item for various predators including shrews, centipedes, toads, spiders, and some birds. Serves as potential host for associated organisms, though specific phoretic relationships remain unconfirmed.

Used in bioactive terrarium and vivarium systems for reptile and amphibian keeping, where they contribute to waste decomposition and soil health. Cultivated in captivity for unusual color morphs. Subject of extensive behavioral research, including studies that inspired the 'Porcellio scaber algorithm' for constrained optimization problems. Common in gardens and urban environments where it contributes to decomposition of organic matter.

• Armadillidium spp.These 'roller' woodlice can conglobate into a ball for defense, unlike P. scaber which adopts tonic immobility; also have smoother exoskeletons
• Porcellio laevisSmooth woodlouse with relatively smooth, less tuberculate exoskeleton compared to the rough surface of P. scaber
• Oniscus asellusCommon European woodlouse with smoother appearance and higher dependence on humid conditions than P. scaber

• woodlouse
• isopod
• crustacean
• detritivore
• personality
• cosmopolitan
• invasive

• BugGuide
• Wikipedia
• GBIF taxonomy match
• iNaturalist taxon
• NCBI Taxonomy
• Catalogue of Life
• Bohart Museum Open House on 'Many Legged Wonders': How Many Legs Does an Isopod Have? | Bug Squad
• Uncategorized | Blog - Part 11
• The bold and the shy one: Could woodlice have personalities? | Blog
• Isopoda | Blog
• Ecdysis in the isopod Porcellio Scaber (Latreille).
• Some observations of correcting behaviour in woodlice (Porcellio scaber)
• Personality affects defensive behaviour of Porcellio scaber (Isopoda, Oniscidea)
• Figure 3 from: Tuf IH, Drábková L, Šipoš J (2015) Personality affects defensive behaviour of Porcellio scaber (Isopoda, Oniscidea). In: Taiti S, Hornung E, Štrus J, Bouchon D (Eds) Trends in Terrestrial Isopod Biology. ZooKeys 515: 159–171. https://doi.org/10.3897/zookeys.515.9429
• The adaptive significance of coprophagous behaviour in the terrestrial isopod Porcellio scaber
• Caenorhabditis elegans nematodes are not attracted to the terrestrial isopod Porcellio scaber
• Architecture of microtubule cytoskeleton in the hindgut cells of Porcellio scaber
• The Humidity Reactions of the Wood-Louse,Porcellio Scaber(Latreille)
• Bacteria associated with the hepatopancreas of the woodlice Oniscus asellusand Porcellio scaber(Crustacea, Isopoda)
• The Ecological Significance of Activity Patterns in the Woodlouse Porcellio Scaber Latr. (Isopoda)