|Electronic field guide to AQUATIC MACROINVERTEBRATES of SMALL STREAMS in Eastern Massachusetts|
|Five pairs of legs; body flattened on top|
|Five pairs of legs; body compressed from sides, shrimp-like.
|Five pairs of legs; body not compressed, but lobster-like; first pair of legs are "pincher" claws (may be broken or missing)|
|Four pairs of legs; body globose, sometimes bright red or blue
|Three pairs of true legs, followed by several pairs of gills that look like legs; front of head with a large pair of jaws (mandibles).