Stream Insects and Crustaceans:
Pictures and Descriptions

Group One Taxa

1. Stonefly: Order Plecoptera. 1/2" - 1 1/2", 6 legs with hooked tips, antennae, 2 hair-like tails. Smooth (no gills) on lower half of body. (See arrow.)
2. Caddisfly: Order Trichoptera. Up to 1", 6 hooked legs on upper third of body, 2 hooks at back end. May be in a stick, rock, or leaf case with its head sticking out. May have fluffy gill tufts on lower half.
3. Water Penny: Order Coleoptera. 1/4", flat saucer-shaped body with a raised bump on one side and 6 tiny legs on the other side. Immature beetle.
4. Mayfly: Order Ephemeroptera. 1/4 - 1", brown, moving, plate-like or feathery gills on sides of lower body (see arrow), 6 large hooked legs, antennae, 2 or 3 long, hair-like tails. Tails may be webbed together.
5. Riffle Beetle: Order Coleoptera. 1/4" , oval body covered with tiny hairs, 6 legs, antennae. Walks slowly underwater. Does not swim on the surface.
6. Gilled Snail: Class Gastropoda. Shell opening covered by thin plate called operculum. Shell usually opens on the right.
7. Dobsonfly (Hellgrammite): Family Corydalidae. 3/4"- 4", dark-colored, 6 legs, large pinching jaws, eight pairs of feelers on lower half of body with paired cotton-like gill tufts along underside, short antennae, 2 tails and 2 pairs of hooks at back end.

    

   Group Two Taxa

   Somewhat pollution tolerant organisms that can be in good or fair quality water.

    

8. Crayfish: Order Decapoda. Up to 6", 2 1arge claws, 8 legs, resembles small lobster.
9. Sowbug: Order Isopoda. 1/4 -3 3/4", gray oblong body wider than it is high, more than 6 legs, long antennae.
10. Scud: Order Amphipoda. 1/4", white to grey, body higher than it is wide, swims sideways, more than 6 legs, resembles a small shrimp.
11. Alderfly Larva: Family Sialidae. 1" long. looks like small hellgrammite but has 1 long, thin, branched tail at back end (no hooks). No gill tufts underneath.
12. Fishfly Larva: Family Corydalidae. Up to 11/2" long. Looks like small hellgrammite but often a lighter reddish-tan color, or with yellowish streaks. No gill tufts underneath.
13. Damselfly: Suborder Zygoptera. 1/2 - 1", large eyes, 6 thin hooked legs, 3 broad oar-shaped tails, positioned like a tripod. Smooth (no gills) on sides of lower half of body.
14. Watersnipe Fly Larva: Family Athericidae (Atherix). 1/4 - 1". Pale to green, tapered body, many caterpillar-like legs, conical head, feathery "horns" at back end.
15. Crane Fly: Suborder Nematocera. 1/3 - 2", milky, green, or light brown, plump caterpillar-like segmented body, 4 finger-like lobes at back end.
16. Beetle Larva: Order Coleoptera. 1/4 - 1", light-colored, 6 legs on upper half of body, feelers, antennae.
17. Dragon Fly: Suborder Anisoptera. 1/2 - 2", large eyes, 6 hooked legs. Wide oval to round abdomen.
18. Clam: Class Bivalvia

     

    Group Three Taxa

    Pollution tolerant organisms can be found in any quality of water.

     

19. Aquatic Worm: Class Oligochaeta. 1/4- 2", can be very tiny; thin worm- like body.
20. Midge Fly Larva: Suborder Nematocera. Up to 1/4", dark head, worm-like segmented body, 2 tiny legs on each side.
21. Blackfly Larva: Family Simulidae. Up to 1/4", one end of body is wider. Black head, suction pad on end.
22. Leech: Order Hirudinea. 1/4 - 2", brown, slimy body, ends with suction pads.
23. Pouch Snail and Pond Snails: Class Gastropoda. No operculum. Breathe air. Shell usually opens on the left.
24. Other Snails: Class Gastropoda. No operculum. Breathe air. Snail shell coils in one plane.

"Bug Sheet" text and illustrations are drawn from Stream Insects and Crustaceans, Save Our Streams, Izaak Walton League of America, 1401 Wilson Blvd. Level B, Arlington, VA 22209. Note: Bar lines below indicate relative size.

Illustrations of Stream Insects and Crustaceans

Return to "Water Fit for a Bug"