The document provides instructions for identifying macroinvertebrates found in freshwater environments. It lists physical characteristics like shells, legs, wings, tails and color in a dichotomous key format to narrow down the type of macroinvertebrate. Selecting characteristics leads the user to a picture of the macroinvertebrate for identification.

1. Instructions
• Click the words that describe the
macroinvertebrate until you have reached a
picture that is the macroinvertebrate you
found.

2. Shell
No shell

3. Double shell
Single shell

4. Small, whitish, tan or brown
Large, 2-8 inches, dark-color

5. Freshwater Muscle

6. Finger Nail or Pill Clam

7. Spiral opening on left
Spiral opening on right
Coiled
Conical

8. Pouch Snail

9. Gilled Snail

10. Orb Snail

11. Limpet

12. Legs
No legs

13. With tentacles brushes or “tails”
Worm like
Microscopic

14. Apostrophe-shaped
Round
Swims with a jerk using antennas

15. Cydops or Copepod

16. Seed and Clam Shrimp

17. Water Flea or Daphnia

18. Suckers expands and contrasts body
segmented
Reddish brown body segmented
Glides along bottom body not segmented
Tan or brown, long
Body with bristles no suckers
Distinct head, red green or tan, twists
Small, hair like swims in “s” shape

19. Leech

20. Tubifex Worm

21. Flat Worm or Planaria

22. Horsehair Worm

23. Bristle Worm

24. Midge Larva

25. Nematode or Threadworm

26. Long breathing tube
Two fringed “tails”
Smooth, “stiff”, small headed
Large, gray with tentacles
White or gray with tentacles
Big “headed”, active
Black, attaches to hard surfaces

27. Rat Tailed Maggot Larva

28. Water Snipe Fly Larva

29. Horse fly Larva

30. Cranefly Larva

31. Cranefly Larva

32. Midge Pupa

33. Black fly larva

34. 10+legs
4 pairs of legs
3 pairs of legs

35. Lobster like
Shrimp-like, swims on side
Walks on bottom

36. Scud or Amphipod

37. Crayfish

38. Aquatic Sowbug or Isopod

39. Tiny often brightly colored
Runs on top of water

40. Water Mite

41. Fishing spider

42. Wings
No wings

43. Beetle-like, wings hard
Leathery wings

44. Small, crawls on bottom
Swims moving hind legs alternating
Back legs move at same time
Swims on surface
“Crawls” through water, spotted

45. Riffle beetle

46. Water Scavenger Beetle

47. Predaceous Diving Beetle

48. Whirligig Beetle

49. Crawling Water Beetle

50. Tan lives on surface
Dark lives on surface
Grasping front legs up to 3 inches
Swims on back, back white
Swims right side up, back black
Long breathing tube, grasping front legs
Long stick-like

51. Marsh Treader

52. Water Strider

53. Giant Water Bug

54. Backswimmer

55. Water Boatman

56. Water Scorpion ‘Nepa’

57. Water Scorpion ‘Ranatra’

58. No obvious “tails”
One or two “tails”
Three “tails”

59. Brown, leather like, 6 legs, usually “c” shaped.
6 legs, and prolegs on abdomen.
Suction cup like.
Large body, hinged mouth.
Green, tan, orange or white body.
Lives in stone case.
Lives in stick house.

60. Riffle Beetle Larva

61. Pyralid Caterpillar

62. Water Penny

63. Dragon Fly Larva

64. No Case Caddisfly Larva

65. Stone Case Caddisfly Larva

66. Wood Case Caddisfy Larva

67. Dark head, green or tan body, two brush like
tails.
Small “spines” on side
Large mouth parts. “spines” on side.
“Tails” long and stiff, long antennas.
Flat gills on abdomen.
Hangs from surface, large mouth parts.

68. Caddisfly Larva

69. Alderfly Larva

70. Dobsonfly Larva

71. Stonefly Larva

72. Mayfly Larva

73. Predaceous Diving Beetle Larva

74. Long “tails” gills on abdomen.
Large legs leathery gills.
Plate like “tails", no gills on abdomen.

75. Mayfly Larva

76. Mayfly larva

77. Damselfly Larva