The World of Aquatic Insects

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The World of Aquatic Insects

• Bill Hall
• University of Delaware
• College of Marine Studies

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What Is Meant by Aquatic Insect?

• Insects that spend at least part of their lives
  associated with aquatic environments
• Almost all leave water for part of their lives,
  usually as adults for reproduction
• Aquatic stages are usually immatures

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• Where do they live?
• Occur in all freshwater environments, some
  brackish, no marine
• How did they get there?
• Insects evolved as terrestrial organisms later
  adapted to freshwater

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Physical factors temperature light current
sedimentsChemical02 pH hardness alkalinity
nutrients
What Physical And Chemical Factors Affect Aquatic
Insects?
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Advantages

• No water loss from evaporation
• Less temperature fluctuation
• Less light, so predators cannot see them
• Avoid competition with terrestrial species

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Disadvantages

• Water uptake from osmosis
• Less oxygen available and in the dissolved state
  (90 saturation is ideal)
• Water is a viscous medium, often moving
• Different food sources
• All can be turned into advantages

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How are aquatic insects adapted for life in
freshwater?
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Breathing

• Bubbles some trap air with hairs or beneath
  wings water boatman, beetles
• Tubes mosquitoes, water scorpion, rat-tailed
  maggot (dronefly larvae)

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• Gills
• Mayfly, stonefly
• Body surface
• midges

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Lifestyle

• Locomotion or maintaining position

Mayfly Larva
Black Fly larva
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• Running Water whirly gig beetles
• Clingers water penny
• No-see-ums

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Water Babies

• Predacious diving beetle direct development
• Mosquito indirect development

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Standing Water

• Striders water tension
• Divers lower O2
• Climbers

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• Tube Builders Caddis Fly

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How Do Aquatic Insects Obtain Food?
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Predators --Engulfers
Dragonfly nymph feeding on the earthworm
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Predators -- Piercers
Backswimmer
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Scrapers
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Shredders
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Collectors
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Reproduction

• Typically egg-larva-adult the larval stage is
  always aquatic
• Some have a pupa stage
• Many have a terrestrial adult stage

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Principles of Ecology and Physiology

• Aquatic insects were originally terrestrial
  organisms that became secondarily adapted to
  exist in freshwater.

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Health Economic Issues

• Some pests
• Mostly blood-feeding species (females) in Diptera
• Some others that emerge synchronously in very
  large numbers
• Health (allergies, secondary infections,
  diseases, loss of life
• Economic (reduced livestock productivity,
  reduced tourism

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Natural Resource Management

• Many species of fish and waterfowl depend on
  aquatic insects for food

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Sport Fishing

• Aquatic insects are the most common models for
  fly fishing---a multimillion dollar business.

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• Some aquatic insects are harvested and used as
  live bait

Helgramite
Dobsonfly
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Conservation Biology
Society has realized the importance of
maintaining biodiversity, including invertebrates
(96 of all animals are invertebrates)

• Some aquatic insects have been deemed worthy of
  special protection (mostly dragonflies and
  damselflies)
• Biocides, larvacides are problematic
  -indiscriminate.

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DRAGONFLY
Common Darter
Hairy Dragonfly
Dragonflies can fly backwards, vertically up- and
downwards and even sidewards.
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Dragonflies are generally larger than
damselflies. At rest they spread their wings
alongside their body. Their eyes touch on top of
their head or the distance between their eyes is
smaller than the width of their eyes.
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Damselflies keep their wings above their back
when resting. The distance between their eyes is
larger than the width of the eyes themselves.
Their body is slimmer and usually shorter than
that of dragonflies.
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Environmental Evaluation
Aquatic insects and other benthic macro
invertebrates have long been used to determine

• If freshwater ecosystems are impaired by
  pollution or other types of environmental stress
• The type of pollution
• The magnitude of pollution
• If an ecosystem recovers after pollution is
  stopped

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This Application Of Aquatic Entomology Is Part Of
Biomonitoring

• Use of biological responses to evaluate changes
  in the environment
• In this case, naturally occurring benthic macro
  invertebrate communities
• Biodiversity the fewer the species

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Gallery
Dobson fly
Backswimmer
Damselfly
Ebony Jewelwing
Hovering Dronefly
Mosquito
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What Everyone Should Know Aquatic Insects as they
are the canaries of wetlands.

• They are mostly fresh water
• They are important to the food chain
• They are important bioindicators of water health