Philoscia muscorum

(Scopoli, 1763)

Common Striped Woodlouse, Fast Woodlouse

Philoscia muscorum is a common European notable for its rapid movement and distinctive appearance. It exhibits a unique strategy called year splitting, where individuals from the same reproductive cohort diverge into two developmental : faster-growing individuals mature and reproduce in their first year, while slower-growing individuals delay maturation until their second year. This has successfully established in eastern North America, including New England, the mid-Atlantic states, and the Pacific Northwest.

Philoscia muscorum by (c) Katja Schulz, some rights reserved (CC BY). Used under a CC-BY license.

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Pronunciation

How to pronounce Philoscia muscorum: //fɪˈlɒskiə ˌmʌsˈkɔːrəm//

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Identification

Distinguished from similar by its faster, more agile movement and elevated body posture. The consistently dark contrasts with the paler, mottled body. Separated from Philoscia affinis by detailed morphological characters requiring close examination. The combination of small size (to 11 mm), shiny surface, and dark head is diagnostic in most of its range.

Images

Appearance

Body reaches up to 11 mm in length. surface is shiny and mottled greyish- in color, though variable may show , red, or orange coloration. The is consistently very dark. The body is raised higher off the ground than other common , an associated with faster .

Habitat

Occupies moist open including meadows and light woodlands. Typically found concealed under stones, within moss clumps, grass tussocks, or leaf litter. Associated with fixed dune grasslands in some .

Distribution

to Europe from southern Scandinavia to Ukraine and Greece, including the British Isles. to North America: established in Washington state, New England states (multiple), Pennsylvania, New Jersey, and Nova Scotia.

Life Cycle

Exhibits year splitting: individuals born in one season differentiate into two developmental forms. Faster-growing individuals reach maturity and reproduce in one year; slower-growing individuals require two years to mature. This creates two distinct year classes from a single reproductive cohort. Growth rate is positively related to ambient temperature and day length. Parental size positively affects offspring number.

Behavior

Moves more rapidly than other common , earning the 'fast woodlouse.'

Similar Taxa

Philoscia affinisMorphologically similar; requires detailed examination to distinguish. The redescription of P. muscorum was partly motivated by the need to clarify separation from this .
Oniscus asellusShares preferences and general appearance, but P. muscorum is smaller, faster-moving, and has a more elevated body posture.

More Details

Evolutionary relationships

Contrary to previous assumptions, P. muscorum is not closely related to tropical and subtropical members of Philosciidae. Instead, it belongs to an evolutionary lineage that includes Oniscus asellus and higher crinochete Oniscidea.

Subspecies

Twelve are currently recognized, though details are not provided in available sources.