Macroinvertebrate Key

GROUP I TAXA: Very intolerant to pollution
1.	Stonefly: Order Plecoptera. 5-35 mm in length. 6 legs with hooked tips, antennae, 2 hairlike tails, smooth, no gills on abdomen.
2.	Dobsonfly: Order Megaloptera, Family Corydalidae. 25-90 mm long. 6 legs, large pinching jaws, tuft-like gills on underside, short antennae.
3.	Snipe Fly: Order Diptera, Family Athericidae. 10-18 mm long. Elongated, cylindrical, with head mostly retracted into thorax, spiny prolegs, two fringed filaments at end of abdomen.
4.	Mayfly: Order Ephemeroptera, Family Leptophlebiidae. 5-15 mm long. Platelike or feathery gills on side of abdomen, 2 or 3 long hair-like tails.

GROUP II TAXA: Somewhat intolerant to pollution and lower DO levels.
5.	Alderfly: Order Megaloptera, Family Sialidae. 10-25 mm long. Light colored, single projection on abdomen, no hooks, filaments on side of body.
6.	Crane Fly: Order Diptera, Family Tipulidae. 10-50 mm long. Short prolegs, ridges on top of bulbous abdomen, no distinct head.
7.	Caddisfly: Order Trichoptera 2-40 mm in length. Hooked legs on upper third of body, 2 hooks on back end. May be in a stick or rock case.
8.	Aquatic Moth: Order Lepidoptera 20-25 mm long. Body with 5 paired knobs on underside of abdominal segments, legs on first 3 segments.
9.	Dragonfly: Order Odonata, Suborder Anisoptera 15-45 mm long. Lower lip is large and covers other mouthparts, large eyes, 3 pairs of legs on thorax.
10.	Damselfly: Order Odonata, Suborder Zygoptera 10-30 mm long. Large eyes, 6 hooked legs, wide oval to round abdomen.
11.	Mayfly: Order Ephemeroptera, Family Heptageniidae 5-20 mm long. Develops in cold clear streams, 2 or 3 hairlike tails, feathery gills along abdomen.
12.	Mayfly: Order Ephemeroptera, Family Caenidae 2-8 mm long. Small hair like gills on abdomen, found in detrital sediments or on thick algae.
13.	Mayfly: Order Ephemeroptera, Family Ephemeridae 12-32 mm long. Feathery abdominal gills and tusks. Lives in silt deposits.
14.	Mayfly: Order Ephemeroptera, Family Oligoneuridae 8-17 mm long. Found primarily in moderate to fast flowing streams, relatively large larvae.
15.	Water Mites: Class Arachnida, Hydracarina Less than 3 mm long. Body compact, spider like with 4 conspicuous pairs of legs.
16.	Water Penny: Order Coleoptera 4-6 mm long. Flat saucer shaped, 6 tiny legs on ventral side.
17.	Riffle Beetle: Order Coleoptera, larva and adult 1-8 mm long. Oval body covered with tiny hairs. 6 legs, antennae.
18.	Scud: Class Crustacea, Order Amphipoda 5-20 mm long. Resembles a small shrimp. Eyes, if present, seen as spots on side of head

GROUP III TAXA: Fairly tolerant to low DO levels and organic nutrients.
19.	Black Fly: Order Diptera, Family Simuliidae 2-8 mm long. One end of the body wider. Black head, suction pad on opposite end.
20.	Deer Fly: Order Diptera, Family Tabanidae 15-40 mm long. No distinct head, cylindrical maggot like body with fleshy rings.
21.	Midge: Order Diptera, Family Chironomidae 2-30 mm in length. Narrow wormlike body with distinct head. One pair of prolegs at each end. Characteristic 'wiggler' movement.
22.	Soldier Fly: Order Diptera, Family Stratiomyidae 10-50 mm long. Distinct head, somewhat flattened body. Often appearing stiff and lifeless.
23.	Gilled Snail: Class Gastropoda 10-40 mm long. Shell opening to the right, covered by a thin operculum.
24.	Sowbug: Class Crustacea, Order Isopoda 5-20 mm long. Gray oblong body, more than 6 legs, long antennae.
25.	Planaria: Class Turbellaria 5-30 mm long. Soft, flat body, crosseyed, spade shaped head.
26.	Asiatic Clam: Class Pelecypoda 10-50 mm long. Hard limestone shells with toothed hinge. Ridged triangular shaped shell. Filter feeder.
27.	Native Clams and Mussels: Class Pelecypoda 2-250 mm long. Shell with membranous hinge.
28.	Biting Midge: Order Diptera, Family Ceratopogonidae 2-15 mm long. Very slender, hairlike body. Often wiggling horizontally.
29.	Crayfish: Class Crustacea, Order Decapoda 10-150 mm long. 8 legs, 2 large claws, resembles lobster.

GROUP IV TAXA: Very tolerant to low DO levels and increased levels of organic nutrients.
30.	Left Handed/Pouch Snail: Class Gastropoda 10-25 mm long. No operculum, shell usually opens to the left.
31.	Segmented Worm: Class Oligochaeta 1-30 mm long. Often red; looks like aquatic earthworm. Can be very tiny, thin segmented body.
32.	Leech: Class Hirudinea 5-50 mm in length. Segmented, suckers on posterior and anterior ends.

Special thanks to Colorado River Watch and LCRA for allowing 4empowerment.com to use this information.

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