16benthic macroinvertebrates- animals without a backbone, visible to the unaided eye, living in or on the stream bottomone of the best indicators of stream healthpresent throughout the yearpopulation reflects environmental changes
17Examples:insects, snails, clams, mussels, crustaceans, worms, and leechesLarge proportion in a stream are insects.
18Insects 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.
19complete metamorphosis- 4 stages (88% of all insects)egg- female insect lays eggslarva- hatch from egg, usually worm-like shape, do not look like adultpupa- inside a cocoon, larva develops adult shape (4 days to months)adult- emerges from cocoon
22incomplete metamorphosis - 3 stages (12% of all insects)egg- female lays eggsnymph- looks like small adult, usually without wings, molt exoskeleton 4-8 timesadult- insect stops molting when adult size is reached and now have grown wings
27-nymphs and larva feed and grow Late Spring/Early Winter Seasonal CycleSummer-eggs hatchFall/Winter-nymphs and larva feed and growLate Spring/Early Winter-adults emerge7
28Stream 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
29Grazers / scrapers-feed on algae-most caddisfly larvae and water pennies-changes in habitat result in an increase of grazers with a decrease of shredders
30Collectors-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
31Predators-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)