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Aquatic Insects. 8 April 2009. Aquatic Insects. Insecta (even Hexapoda) are plesiomorphically terrestrial . But there have been numerous colonizations of the freshwater aquatic environment. Far fewer colonizations of marine aquatic environment. Hemimetabolous Aquatic Insects.

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aquatic insects

Aquatic Insects

8 April 2009

aquatic insects1
Aquatic Insects
  • Insecta (even Hexapoda) are plesiomorphically terrestrial.
  • But there have been numerous colonizations of the freshwater aquatic environment.
  • Far fewer colonizations of marine aquatic environment.
hemimetabolous aquatic insects
Hemimetabolous Aquatic Insects
  • Some lineages have almost* exclusively aquatic naiads.
    • Ephemeroptera
    • Odonata*
    • Plecoptera (the only aquatic Polyneoptera)
  • All of these have terrestrial adults.
hemimetabolous aquatic insects1
Hemimetabolous Aquatic Insects
  • There are multiple colonizations of aquatic environments by Heteroptera.
  • Most of these are also aquatic as adults.
holometabolous aquatic insects
Holometabolous Aquatic Insects
  • Colonized aquatic environments much more recently.
  • Numerous colonizations within numerous orders
  • Only two have exclusively* aquatic larvae.
  • Only some Coleoptera remain aquatic as adults.
holometabolous aquatic insects1
Holometabolous Aquatic Insects
  • Neuroptera: One lineage (Sisyridae, spongillaflies).
  • Coleoptera: Numerous colonizations throughout.
  • Diptera: Numerous colonizations, especially in Nematocera.
  • Lepidoptera: Numerous origins, but NOT common
habitats for aquatic insects
Habitats for aquatic insects
  • Lotic: flowing water
    • Influenced strongly by velocity of flow
      • Particle size
      • Substrate type
    • Inputs from outside and local nutrient supplies
  • Lentic: standing water
    • Often strong zonation
      • Limnetic zone- penetrated by light
      • Profundal zone- deeper zone w/o much light
unusual habitats
Unusual Habitats
  • Marine environments
    • Intertidal habitats
      • Between high and low tide
      • biting flies, plant feeding insects, detritivores
    • Littoral habitats
      • Coastal regions with shallow water
      • Some midges and beetles
    • Open ocean: water striders feeding on food of terrestrial origin
  • RARE! WHY???
unusual habitats1
Unusual Habitats
  • Temporal water bodies (e.g. vernal pools)
    • Common in areas with seasonal rainfalls
  • Numerous adaptations
    • Ability to find ephemeral pools (meteorological cues?)
    • Desiccation resistant diapause
      • Very common as eggs
      • Some with ability to undergo numerous dehydrate/rehydrate cycles: anhydrobiosis
  • Plant container habitats: Phytotelmata
oxygen supplies
Oxygen Supplies
  • Air: 200,000 ppm (20%)
  • Lotic environments (15 ppm)
    • Depends on O2 production/consumption by plants
    • Affected by turbulence and water quality
  • Lentic environments
    • Oxygen levels vary with temperature, salinity, and depth
    • Turbulence affects nutrient and oxygen distribution
  • Anoxic
    • No oxygen present
how do aquatic insects obtain oxygen
How do aquatic insects obtain oxygen?
  • Atmospheric oxygen
    • Keep part of body out of water
    • Carry oxygen into water
  • Aqueous oxygen
    • Use of open tracheal system
      • Adult insects
      • Immature forms
    • Use of closed tracheal system
      • Specialized structures for gas exchange in water
      • Often adults have open tracheal system
closed tracheal system
Closed Tracheal System
  • Gills- lamellar extensions of tracheal system
  • Found in many insect orders
  • Gills may be in many places
    • Base of legs
    • Abdomen
    • End of abdomen
    • How is this analogous to insect ears?
open tracheal system in flies
Open tracheal system in flies
  • Respiratory siphons near abdomen or thorax
  • Different location in mosquito pupa than larva
open tracheal system in diving beetles
Open tracheal system in diving beetles
  • Bubble stored beneath elytra
  • Gas exchange can occur in water

Does the bubble increase linearly with oxygen consumption?

What happens to the exhalation product?

other air bubble gills
Other air bubble gills
  • Water kept away from body through ‘hairs’ or ‘mesh’
  • Oxygen diffuses from water to air against body
  • Usually slow moving insects with low oxygen demand
lotic adaptations
Lotic Adaptations
  • Flattened bodies
  • Attachment through suckers

Water pennies (Coleoptera: Psephenidae)

Net-winged midges

(Diptera: Blephariceridae

more lotic adaptations
More Lotic Adaptations
  • Nets & Cases

Trichoptera net

Trichoptera cases

lentic adaptations
Lentic Adaptations

Water Strider (Gerridae)

  • Taking advantage of surface tension of still water

Whirligig Beetle (Gyrinidae)

adaptations to nearly anoxic environments
Adaptations to nearly anoxic environments
  • Hemoglobins
    • Many larval chironomid midges (Diptera) = bloodworms
    • Some notonectid bugs (Heteroptera) = backswimmers
    • Very, very high affinity for oxygen (unlike us)
    • Only downloads when oxygen concentrations in tissues decrease, not when tissues become acidic
using insects to monitor aquatic environments
Using insects to monitor aquatic environments
  • Usefulness
    • Diverse taxa to choose from, many common
    • Functionally important to ecological community
    • Ease of sampling many individuals without major ethical constraints
    • Ability to identify species
  • Responses
    • Increases of certain taxa in waters with sediment, low
    • Oxygen, increases in temperature
    • Loss of diversity with pollution and or eutrophication
  • Naiads often with abdominal gills
    • Also maxillary and labial gills!
  • Generally 3 styli on naiads and adults.
  • As many as 45 instars
  • Anything else?
  • Dragonflies & Damselflies
  • Rectal/anal internal gills.
  • Caudal lamellae also serve as gills.
  • Up to 20 instars.
  • Predators as naiads and adults.
  • Mostly temperate regions
  • 10-33 instars
  • Closed tracheal system with anal gills.
  • Need high oxygen, good environmental indicators.
hemiptera true bugs
Hemiptera: True Bugs



  • Diving or at surface
  • Adults and naiads both aquatic.
  • Highly modified legs.
  • Generally wings still functional as adults, can disperse between waterways.


Water Boatmen


Creeping water bugs


Water striders

  • Left: Nepidae (water scorpions) tails are breathing tubes
  • Right: Belostomatidae (toe-biters) egg tending by males
  • Case & net makers.
  • Abdominal tracheal gills.
  • Aquatic larvae, aquatic adults
  • Aquatic larvae, terrestrial adults
  • Terrestrial larvae, aquatic adults
  • Pretty much all pupate on land
  • Often with anal spiracles breathing at surface
  • Very diverse
  • Almost all disease vectoring Diptera have aquatic larvae (?)