Common Pill Woodlouse vs Isopod

Armadillidium vulgare compared with Armadillidium nasatum

Key Differences

• Common Pill Woodlouse is Near Threatened while Isopod is Not Evaluated.

Taxonomic Classification

Rank	Common Pill Woodlouse	Isopod
Kingdom same	Animalia (동물)	Animalia (동물)
Phylum same	Arthropoda (절지동물)	Arthropoda (절지동물)
Class same	Malacostraca (연갑강)	Malacostraca (연갑강)
Order same	Isopoda (등각류)	Isopoda (등각류)
Family same	Armadillidiidae	Armadillidiidae
Genus same	Armadillidium	Armadillidium
Species	Armadillidium vulgare	Armadillidium nasatum

Evolutionary Relationship

Common Pill Woodlouse and Isopod share a common ancestor at the Genus level: Armadillidium.

Conservation Status

Common Pill Woodlouse

NT — Near Threatened

Isopod

NE — Not Evaluated

Physical Characteristics

Attribute	Common Pill Woodlouse	Isopod
Diet	—	—
Average Lifespan	—	—
Average Length	—	—
Average Weight	—	—

Habitat & Geographic Range

Common Pill Woodlouse

Habitat

Typically found in marine, freshwater, and terrestrial environments.

Range

Widely distributed across Africa (South Africa), Asia (Japan), Europe (6 countries), and North America (United States). Listed as Near Threatened, this species requires ongoing monitoring to prevent population decline.

Isopod

Habitat

Typically found in marine, freshwater, and terrestrial environments.

Range

Widely distributed across Asia (Japan), Europe (12 countries), and North America (United States).

Common Pill Woodlouse

<em>Armadillidium vulgare</em>, the common pill woodlouse, is a terrestrial isopod crustacean in the family Armadillidiidae, widely recognised for its ability to roll into a tight sphere when disturbed, a defensive behaviour that gives it the common name "pill bug" or "roly-poly." Unlike most crustaceans, it is fully adapted to life on land, breathing through modified gill-like structures that must remain moist. The species inhabits a broad range of environments, typically occurring under rocks, leaf litter, decaying wood, and in gardens and agricultural land, where it feeds on decomposing organic matter, playing an important role in nutrient cycling. <em>Armadillidium vulgare</em> is distributed across Europe, parts of Asia including Japan, South Africa, and North America including the United States, reflecting its success as a cosmopolitan species often transported inadvertently by human activity. It is assessed as Near Threatened on the IUCN Red List. Biological traits such as average lifespan, precise body dimensions, and detailed dietary composition across its range remain poorly documented in the scientific literature. Females brood their young in a marsupium, and the species is capable of parthenogenesis under certain conditions, contributing to reproductive flexibility.

Shared Countries

Both species can be found in 6 countries:

🇧🇪 Belgium 🇩🇰 Denmark 🇯🇵 Japan 🇳🇴 Norway 🇸🇪 Sweden 🇺🇸 United States