|Electronic field guide to AQUATIC MACROINVERTEBRATES of SMALL STREAMS in Eastern Massachusetts|
|No gills on abdominal segment 1; first set of gills (on abdominal segment 2) operculate, covering the other gills.CAENIDAE|
|No gills on abdominal segments 1 to 3; first set of gills (on segment 4) operculate, covering part or all of the other gills.
|Gills appear long and sharply pointed; most gills deeply forked, appearing doubled.LEPTOPHLEBIIDAE|
|Head and body wide and flattened, eyes located on top of head; last pair of gills narrow and pointed, projecting out from each side near rear of abdomen.HEPTAGENIIDAE
|Gills appear small and rounded, with a dark band along the side margins.AMELETIDAE|
|Gills rounded, with darkened centralized veins.SIPHLONURIDAE