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For Insects, Spiders & Their Kin
For the United States & Canada
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Species Oniscus asellus - European Sowbug

Isopod - Oniscus asellus Sowbug Head - Oniscus asellus Oniscus asellus - European Sowbug? - Oniscus asellus European Sowbug - Oniscus asellus woodlouse - Oniscus asellus Isopod I1 - Oniscus asellus Porcellio scaber Maybe ? - Oniscus asellus European Sowbug - Oniscus asellus
Kingdom Animalia (Animals)
Phylum Arthropoda (Arthropods)
Subphylum Crustacea (Crustaceans)
Class Malacostraca (Malacostracans)
Superorder Peracarida (Peracarida (Amphipods and Isopods))
Order Isopoda (Isopods)
Suborder Oniscidea (Woodlice)
Infraorder Holoverticata
No Taxon (Orthogonopoda)
No Taxon (Crinocheta)
Family Oniscidae (Sowbugs)
Genus Oniscus
Species asellus (European Sowbug)
Other Common Names
Woodlouse (UK)
Up to 16 mm long and up to 6 mm wide.
Flat, brown-black with pale mottling and pale edges to the segmental plates. The body ends in a two-pointed segment - the telson.
- shiny, even surface, greyish colour with white margins, sometimes with little yellow dots.
- wide oval shape, and the body is quite flat
- 3 segments of the flagellum, long antennae
- no significant protrusion or middle lobe on the head (compared to: Porcellio scaber, where you find an apiculate protrusion in the middle)
- no "lungs" ("white bodies") >>> Porcellio scaber has 2 pairs on the abdomen, ventral side.
- at first it doesnt run away, but clings on the surface (that's why it belongs to the "clinger type" isopods)
Dark damp places with rotting organic matter - their favorite place in a garden is usually the compost heap, where they are very effective decomposers. Can reliably be found under rocks and logs, too.
Dead organic matter, animal waste or rotting wood and other plant material.
Not harmful to humans, rather helpful in cleaning up plant waste etc. Occasionally reported to eat garden plants, but generally considered beneficial.
Internet References
The Pied - a site maintained by a British pest control company, but good information.
Sowbugs and Pillbugs an informative Bug of the Month article fom a bug-lovers' club (Scarabs: The Bug Society) in Puget Sound.