11

Benthic Benthic MacroinvertebratesMacroinvertebrates

IdentificationIdentification

22

BackswimmerBackswimmer

33

Caddisfly LarvaCaddisfly Larva

44

Crane FlyCrane Fly

55

CrayfishCrayfish

66

DamselflyDamselfly

77

DamselflyDamselfly

88

DragonflyDragonfly

99

HellgrammiteHellgrammite

1010

MayflyMayfly

1111

MayflyMayfly

1212

StoneflyStonefly

1313

Water BoatmanWater Boatman

1414

Water PennyWater Penny

1515

Water StriderWater 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

1717

Examples:

insects, snails, clams, mussels, crustaceans, worms, and leeches

Large proportion in a stream are insects.

1818

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.

1919

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

2020

egg

larva

pupa

adult

2121

2222

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

2323

eggnymph

adult

2424

2525

Complete metamorphosis orders(species)

• Tricoptera (caddis flies)

• Megaloptera (dobsonflies, fish flies, alderflies)

• Coleoptera (beetles)

• Diptera (true flies)

2626

Incomplete metamorphosis orders(species)

• Ephemeroptera (mayflies)

• Plecoptera (stone flies)

• Odonata (dragonflies, damselflies)

• Hemiptera (true bugs)

2727

Seasonal Cycle

• Summer -eggs hatch

• Fall/Winter

-nymphs and larva feed and grow

• Late Spring/Early Winter-adults emerge

77

2828

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

2929

•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

3030

•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

3131

•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)