Taxonomic Guide to Isopods of North America

by Sequoia J. Wrens

Caecidotea racovitzai s. str. (Great Lakes Waterslater) by Sequoia J. Wrens

At this point in time, the guide to Isopods is incomplete. However, guides and keys down to family have been completed (aside from illustrations), and these keys are made public to assist with isopod identification before the family, genera and species guides are completed. Family guides and lower will be released as they are completed.
This guide is the culmination of over 2 years of nearly nonstop work by the author to compile as many resources on isopods as possible and is the first attempt to consistently document and illustrate the fauna in the region since Richardson's 1905 monograph. A much larger guide, with complete accounts to all +10800 species of isopods worldwide, is also under construction, with this guide serving as a prototype to the methods that will eventually be used in FAUNA ISOPODA: A complete guide to the world's Isopods.

The taxonomic guide covers all of North America down to Panama and Grenada. It includes most of the Northwest Atlantic, a large portion of the Northeast Pacific and remote islands including the Bering Sea and Aleutian Islands (excluding Komandorski), Bermuda and Cocos Island. It excludes the Arctic Ocean (except the southern part of the Davis Strait), the Southern Caribbean islands fringing the north shore of South America (Aruba, Bonaire and Curaçao) and Trinidad & Tobago.

If there are any errors in the accounts, please let us know! The taxonomic guide is still a work in progress so many errors are likely to slip by the author's attention.

Introduction to Isopods

Taxonomy of Isopods

Morphology of Isopods [under construction]

How to use the Guide [under construction]

Start of Key (Isopoda order account)

Taxonomic Tree to Families

Map Plates [under construction]


Glossary of Terms 


Richardson, H. (1905). A monograph on the isopods of North America. Bulletin of the U.S. National Museum, 54.

Sources used throughout the guide

Martin, J.W., N.D. Pentcheff, D. Striley, C. Perrodin, A.R. Wall, J. Wall, and J. Zieba (editors). Crustacea Glossary. Crustacea Department, Natural History Museum of Los Angeles County. URL:

WoRMS Editorial Board (2023). World Register of Marine Species. Available from at VLIZ. doi:10.14284/170

Published: Jan 1, 2023
Updated: Nov 1, 2023