Identification, Images, & Information
For Insects, Spiders & Their Kin
For the United States & Canada
Clickable Guide
Moths Butterflies Flies Caterpillars Flies Dragonflies Flies Mantids Cockroaches Bees and Wasps Walkingsticks Earwigs Ants Termites Hoppers and Kin Hoppers and Kin Beetles True Bugs Fleas Grasshoppers and Kin Ticks Spiders Scorpions Centipedes Millipedes


Order Isopoda - Isopods

Unknown Bug - Porcellio spinicornis Pill Bug - Armadillidium vulgare Another Elk Grove Woodlouse - Porcellio laevis Idotea metallica - male - female Armadillidium nasatum European Sowbug ? - Oniscus asellus Isopoda - Armadillidium vulgare unknown - Lirceus
Kingdom Animalia (Animals)
Phylum Arthropoda (Arthropods)
Subphylum Crustacea (Crustaceans)
Class Malacostraca (Malacostracans)
Superorder Peracarida (Marsupial Crustaceans)
Order Isopoda (Isopods)
Other Common Names
cressbug, pillbug, sowbug, woodlouse, rock slater, roly-poly
Explanation of Names
Isopoda Latreille 1817
>10,200 spp. worldwide(1) (but probably much more, many checklists seem to underestimate the number of recorded species), >1200 in our area; 11 suborders total, 7 represented in North America
2 to >300* mm (*Bathynomus, a deep sea genus)
key to NA taxa to family level (with species keys under construction) in (2)
key to OH spp. in(3)
from deep sea to terrestrial habitats
Life Cycle
Wood lice protect and brood their eggs in a ventral pouch until they hatch.(4)
Wood lice have inconspicuous channels on their cuticles for water uptake via capillary action. This water is then passed over their gills and excreted along with ammonia. The toxic ammonia evaporates quickly.(4)
See Also
Amphipods are usually laterally compressed (although some aquatic isopods can be too) and have 3 sets of uropods
Insects only have six legs; the isopod group with the least number of legs (Gnathiidae) has 10 legs and most isopods have 14 legs
Myriapods have numerous leg pairs and lack the strong tagmosis (formation of distinct "zones" of modified body segments) that occurs in isopods
Print References
Internet References
Coastal Isopods of California (Brusca et al. 2001)
Taxon profile (Brusca 1997)