With a special focus on Mayflies, Caddisflies, and Stoneflies

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Aquatic Entomology Benthic Macroinvertebrates

• With a special focus on Mayflies, Caddisflies,
  and Stoneflies

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Why are there so many insects around streams,
rivers, and lakes?

• Aquatic insects spend the majority of their lives
  in water.
• Hatch in/under water
• Live for a large percentage of their life under
  water getting bigger.
• When they are ready for adulthood they rise/crawl
  to the surface to molt and begin the adult
  portion of their life above the surface
• At this point their primary goal is to reproduce

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Why look at invertebrates?

• An immediate indication of water quality can be
  seen just by observing what is living in in it.
• Invertebrates are broken down into 3 taxons
• 1) Pollution sensitive
• 2) Somewhat- sensitive
• 3) Tolerant
• What if you find no sensitive organisms in a
  stream?
• Diversity is key!
• When fishing they help you understand what
  insects are present and therefore what the fish
  may feed on.

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Benthic Macroinvertebrates

• Benthic- Bottom dwelling
• Macro- large
• Invertebrate- spineless organism
• Large bottom-dwelling spineless organism
• Most are found in the substrate or on the bottom
  of rocks. Scrapers, Shredders
• Some are climbers- climb up on plant and stems
• For fishing we will look at when they are below
  and above water.

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Invertebrate Classification

• Taxonomy- science of naming and classifying
  organisms
• Each organism is given a two part name consisting
  of a Genus(noun) and a species(adjective)

• Kingdom
• Phylum
• Class
• Order
• Family
• Genus
• Species

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Insect Identification

• Insect identification begins with the Class-
  Insecta
• Then is divided into more specific orders.
• Three important examples are
• Mayfly ephemeroptera
• Caddisfly Trichoptera
• Stonefly plecoptera
• A dichotomous key is often used for insect
  identification
• This tool uses a list of identifiable
  characteristics to group organisms into related
  taxons

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Adult Mayfly

• Note the Sailboat wings

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Adult Caddisfly

• Note the tent wings

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Adult Stonefly

• Note the size and flat wings

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Insect Life Cycles

• Most insect invertebrates found in a stream are
  in some stage of metamorphosis
• All insects undergo some type of Metamorphosis
  (series of life changes from the egg to the
  adult)
• Two types- 1) complete 2) incomplete

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Complete Metamorphosis

• Four stages
• 1) egg
• 2) Larva- all insects have the post embryonic
  larval stage
• 3) pupal- transitional stage, stationary cocoon
  or mobile
• 4) Adult- above water
• Ex. Butterfly

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Incomplete Metamorphosis

• Has no Pupal stage
• Larval stage is characterized by a series of
  molts
• Periods between molts are called instars
• Insect is sometimes referred to as a nymph or
  naiad during the larval stage

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Metamorphosis for the beginning fly fisher
(Caddis example)

• Caddis nymph
• Adult Caddis

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Mayfly Life Cycle
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How do most fly fishers refer to insect life
cycles?

• Nymph Bottom dwelling version
• Pupae Worm-like stage
• Emerger Making its way to the surface
• Adult Normal flying version
• Spinner Laying eggs

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What life cycle stage should I fish with?

• It depends on quite a few things
• What are the fish feeding on
• Do you like fishing a dry fly or nymph?
• What is your fly selection?
• Trout get 90 of their food underneath the
  surface. Nymphing is more productive!

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Invertebrate Sampling

• Kick net- large net used to sample a 3x3 area
  in a riffle(current in a stream)
• 1) Place the net in a riffle, weight down the
  bottom to prevent escaping underneath
• 2) pick up and rub large rocks, place aside
• 3) Stir the substrate by kicking thoroughly with
  your feet
• Grab net- lower right
• Most fishers will turn over rocks or run their
  hands through the bushes to try to locate bugs