Bug FAQRockweed isopod
Pentidotea wosnesenskii · Order: Isopoda · Family: Idoteidae
The rockweed isopod can grow up to about 4 cm long.
Source: Wikipedia
Size
Adults reach up to 4 cm (1.6 in) in length.
Source: Wikipedia
Where it lives
Found on seaweed on rocky shores of the British Columbia and Washington coasts, extending south to San Francisco.
Source: Wikipedia
Where it comes from
Native to the Pacific coast of North America, from British Columbia and Washington down to San Francisco.
Source: Wikipedia
Where it is found in the US
Recorded in 4 of 51 states and DC. Most records: Washington, Alaska, California, Oregon.
Darker = more records. Counts are museum and citizen-science records, not population size.
Source: GBIF
Status: native in North America; native in Canada. Source: iNaturalist
Months it is reported in the US
Source: GBIF
More photos
Sources
- Wikipedia: https://en.wikipedia.org/wiki/Pentidotea_wosnesenskii
Look it up elsewhere: GBIF · iNaturalist · BugGuide · ITIS · Wikipedia
Text written 2026-10-23 from the sources above and checked sentence by sentence against them. Data fetched 2026-10-23.