Benthic Macroinvertebrates

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Benthic Macroinvertebrates

• Identification

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Backswimmer
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Caddisfly Larva
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Crane Fly
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Crayfish
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Damselfly
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Damselfly
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Dragonfly
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Hellgrammite
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Mayfly
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Mayfly
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Stonefly
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Water Boatman
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Water Penny
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Water Strider
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• 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

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Examples insects, snails, clams, mussels,
crustaceans, worms, and leeches Large proportion
in a stream are insects.
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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.
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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
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egg
larva
pupa
adult
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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
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egg
nymph
adult
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• Complete metamorphosis orders(species)
• Tricoptera (caddis flies)
• Megaloptera (dobsonflies, fish flies, alderflies)
• Coleoptera (beetles)
• Diptera (true flies)

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

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

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• 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

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• 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

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• 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

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• 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)