Biphasic-moulting
Guides
Oniscus asellus
common woodlouse, common shiny woodlouse, European sowbug
Oniscus asellus is a large terrestrial isopod native to Western and Northern Europe, and one of the most widespread woodlouse species in the British Isles. It reaches up to 16 mm in length and inhabits diverse moist environments, including rotting wood, gardens, and human structures. The species exhibits biphasic moulting, consuming its shed exoskeleton, and has been documented to fragment weathered polystyrene plastic into microplastics. Two subspecies are recognized: the widespread O. a. asellus and the smaller, more colorful O. a. occidentalis in western France and southeastern Britain.