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Macroinvertebrates

Aquatic Worm

Pollution-Tolerant
  • Moves by stretching and pulling its body along in a worm-like fashion
  • May be red, tan, black or brown
  • Can look like an earthworm or be much narrower and thread-like
  • Segmented body
  • Up to five inches long
  • May have short bristles or hairs that help with movement, but are not usually visible
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    Black Fly Larva

    Pollution-Tolerant
  • Up to 1/3 inches long • The head is usually black, but sometimes brown, tan or green
  • One very tiny leg-like appendage directly under the head
  • Attachment disks (small suckers) on the end of the abdomen
  • The body is segmented
  • Back end of the body widens and is bulbuous
  • No legs
  • Tiny gills by head filter food from water
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    Leeches

    Pollution-Tolerant
  • Only a few are parasites on humans
  • Leeches that attach to humans are not found in fast moving water or riffle areas
  • Many are scavengers or feed on other invertebrates
  • Suckers at both ends are used for attachment, feeding, and locomotion
  • They swim gracefully and quickly in an up-and-down motion
  • They move by attaching suckers from end to end
  • Worm-like, segmented body
  • Body is somewhat flat
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    Midge Larva

    Pollution-Tolerant
  • Almost 2000 species in North America
  • Are found in all but the most polluted aquatic conditions
  • Presence in large numbers may indicate organic enrichment
  • Up to 1/2 inches long
  • One pair of tiny, fleshy legs below the head and one pair on the back end
  • The back end sometimes has a tin pair of extensions that look like brushes
  • A thin dark line (digestive tract) can be seen inside the body
  • Distinct, often dark head
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    Pouch Snail

    Pollution-Tolerant
  • They get oxygen directly from air trapped in their shell cavity and thus are less dependent on water quality
  • Shell is made of calcium carbonate
  • It’s important that the snail is alive (someone is at home) before counting it in a survey
  • Shell is spiral, coil or dome shaped
  • Has no operculum (plate-like door)
  • Shells usually open on the left side, which can be seen if you hold the shell with its tip pointing up and the opening facing you
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    Beetle Larva

    Exist in a Wide Range of Conditons
  • Up to 3/4” long
  • Body is long, hard, stiff and segmented
  • Six long segmented legs on upper middle section of body
  • Back end has two tiny hooks and short hairs (may be hard to see)
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    Crayfish

    Exist in a Wide Range of Conditons
  • They grow by shedding (“molting”) their shells
  • Often found hiding under rocks during the day and foraging on the stream bed during the night
  • Most live only two years, but some may live up to six or seven years
  • Up to six inches long
  • Eyes stand out from the body
  • Two or four antennae
  • Body covered with hard, platelike shell
  • Ten legs, two of these are large claws
  • Color is red, orange, brown
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    Clam

    Exist in a Wide Range of Conditons
  • Wide range of tolerances to pollution; some are very sensitive
  • Mussels have a long life span
  • Two hinged shells enclose soft bodies
  • Clams are smaller (3/4 inches) and more round than mussels
  • Clams are usually symmetrical with the umbo (highest point on the shell) equally distant from both ends
  • Mussels have a flat, oblong shell shape
  • Soft, fleshy body (foot) may be seen extending from shell
  • No eyes or distinct head
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    Cranefly Larva

    Exist in a Wide Range of Conditons
  • Develop over a period of six weeks to five years
  • Close to 300 species in North America
  • Usually live in the stream bed
  • Up to four inches long
  • Head is usually retracted so the front end appears round
  • Fleshy, plump, rounded segmented body
  • Its digestive track (internal organs) can be seen moving back and forth as it crawls
  • No legs
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    Damselfly Larva

    Exist in a Wide Range of Conditons
  • Develop over one to four years
  • Large eyes • Large scoop-like lower lip
  • No gills on the sides or underneath the abdomen
  • Six long segmented legs on upper middle section of body
  • Long spindly legs
  • Narrow body with three oar-shaped tails (gills) that look like fans
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