Benthic Macroinvertebrates Identification

Backswimmer

Caddisfly Larva

Crane Fly

Crayfish

Damselfly

Damselfly

Dragonfly

Hellgrammite

Mayfly

Mayfly

Stonefly

Water Boatman

Water Penny

Water Strider

benthic macroinvertebrates- animals without a backbone, visible to the unaided eye, living in or on the stream bottom one of the best indicators of stream health present throughout the year population reflects environmental changes

Examples: insects, snails, clams, mussels, crustaceans, worms, and leeches Large proportion in a stream are insects.

Insects go through metamorphosis (life changes) from egg to adult. Due to these life cycles, the size and abundance of insects present in a stream will vary with the season. Insects have a rigid exoskeleton that must be replaced in order for them to grow.

complete metamorphosis- 4 stages (88% of all insects) egg- female insect lays eggs larva- hatch from egg, usually worm-like shape, do not look like adult pupa- inside a cocoon, larva develops adult shape (4 days to months) adult- emerges from cocoon

egg larva pupa adult

incomplete metamorphosis - 3 stages (12% of all insects) egg- female lays eggs nymph- looks like small adult, usually without wings, molt exoskeleton 4-8 times adult- insect stops molting when adult size is reached and now have grown wings

egg nymph adult

Complete metamorphosis orders(species) Tricoptera (caddis flies) Megaloptera (dobsonflies, fish flies, alderflies) Coleoptera (beetles) Diptera (true flies)

Incomplete metamorphosis orders(species) Ephemeroptera (mayflies) Plecoptera (stone flies) Odonata (dragonflies, damselflies) Hemiptera (true bugs)

-nymphs and larva feed and grow Early Spring/ Late Winter Seasonal Cycle Summer -eggs hatch Fall/Winter -nymphs and larva feed and grow Early Spring/ Late Winter -adults emerge 7

Stream Communities and Feeding Groups Shredders -macroinvertebrates with chewing mouth parts -feed on decaying organic matter processes into finer particles -aquatic sowbugs, a few caddisfly larvae, some cranefly larvae, scuds, and most stonefly nymphs

Grazers / scrapers -feed on algae -most caddisfly larvae and water pennies -changes in habitat result in an increase of grazers with a decrease of shredders

Collectors -feed on fine organic particles -blackfly larvae, most caddisfly larvae, mayfly nymphs, midge larvae, riffle beetles, and riffle beetle larvae -collectors are found in all stream regions, but are dominant in the lower regions of a stream system

Predators -feed on prey -alderfly larvae, backswimmers, most beetles and beetle larvae, damselfly nymphs, dobsonfly larvae (hellgrammites), dragonfly nymphs, fishfly larvae, some stonefly nymphs, and some cranefly larvae -predators are found in all stream regions (wherever prey is found)