THE XERCES SOCIETY FOR INVERTEBRATE CONSERVATION

Aquatic Invertebrates in Pacific Northwest Freshwater Wetlands
An Identification Guide and Educational Resource

Diptera
(fly larvae)
Iincredibly diverse group; heads may be hard and well-developed or reduced to a few dark rods; may have fleshy legs (1 to many) or suckers; only group on this page that has any sclerotized regions

Turbellaria
(flatworms)

Flattened dorsoventrally; delicate, soft, and unsegmented, glide easily on rocks; triangular, arrow-shaped head, often with 2 eyespots that give a cross-eyed look

Nematoda
(hook worms)

Small, unsegmented, worm-like organisms with tough bodies; usually white and sometimes poking out of another macroinvertebrate that they have parasitized

Nematomorpha
(horsehair worms)

Very long, tough, unsegmented, wiry worm-like animals; sometimes found tangled in writhing masses

Nemertea
(ribbon worms)

Medium-sized, soft bodied, unsegmented worm similar to flatworms but with a pore at each end and an eversible proboscis (feeding tube) that may be extended from head

Cnidaria
(hydra)

Small, soft, round body with several tentacles.

Ectoprocta
(Bryozoa or moss animals)

Floating colonies of tiny organisms; squishy, spongy or moss-like.