The phyllodocida span a range of habitats. While most are marine, some live in brackish waters, and members of the family Nereididae can be found in freshwater and even terrestrial environments. The Phyllodocida make up a large portion of what have been considered the “errant” polychaetes – active burrowing and swimming worms. Most of the marine members of the Phyllodocida are free-living burrowers; some groups spend their adult lives in the water column (these pelagic species are usually transparent). A very few are sessile and live in tubes (Pleijel and Rouse 2004).