Key To Macroinvertebrates in

Rivers and Streams

Shell Present

Shell Absent

Shells

Single Shell (snails)

Double Shell

“Shell” with legs

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Snails

Group I Group III

Group IIClams & Mussels

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No Legs

Wormlike

With tentacles, brushes or “tails”

Legs Present

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Group IIILeeches

Group IIIOther Worms

Group IIIMidge Larvae

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Group IICrane Fly, Horse Fly, Deer Fly Larvae

Group IIIBlack Fly Larvae

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Legs Present

Ten + Legs

Three Pairs of Legs

Four Pairs of Legs

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Crustaceans

Group IICrayfish - Decapods

Group IIScuds or Side swimmers - Amphipods

Group IISowbugs - Isopods

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Wings Present – Adult Insects

Wings Absent – Insect Larvae or Nymphs

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Beetle – like InsectsWings hard

Other InsectsWings leathery

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Beetle – like InsectsWings hard

Group I

Not counted in index – record on data sheet

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Other InsectsWings leathery

Not counted in index – record on data sheet

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Firmly attached to rocks

Obviously free moving

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Group IGroup III

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“Tail” filaments present

“Tail” filaments absent

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Group II

Group II

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One or two “Tail” filaments

Three “Tail” filaments

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Elongated body, extra “appendages”

Six legs, obviously insects

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Group I

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Group II

Group IGroup IGroup II

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Other Beetle Larva

Group IGroup II

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Four Pairs of Legs

Not counted in index – record on data sheet

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Images from the following source:

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