Aquatic Insect Orders

Aquatic Insects

• Insects are largely terrestrial.

• But there have been numerous colonizations of the freshwater aquatic environment.

• Far fewer colonizations of marine aquatic environment.

Aquatic Insects

• Some lineages have almost* exclusively aquatic naiads.– Ephemeroptera– Odonata*– Plecoptera

• All of these have terrestrial adults.

Ephemeroptera

• Naiads often with abdominal gills– Also maxillary and

labial gills!

• Generally 3 styli on naiads and adults.

• As many as 45 instars

• Anything else?

Odonata

• Dragonflies & Damselflies

• Rectal/anal internal gills.

• Caudal lamellae also serve as gills.

• Up to 20 instars.• Predators as naiads

and adults.

Plecoptera

• Mostly temperate regions

• 10-33 instars• Closed tracheal

system with anal gills.

• Need high oxygen, good environmental indicators.

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.

Notonectidae:Backswimmers

Corixidae:Water Boatmen

Naucoridae:Creeping water bugs

Gerridae:Water striders

Hemiptera

• Left: Nepidae (water scorpions) tails are breathing tubes

• Right: Belostomatidae (toe-biters) egg tending by males

Trichoptera

• Case & net makers.• Abdominal tracheal gills.

Coleoptera

• Aquatic larvae, aquatic adults

• Aquatic larvae, terrestrial adults

• Terrestrial larvae, aquatic adults

• Pretty much all pupate on land

Diptera

• Often with anal spiracles breathing at surface

• Very diverse• Almost all disease

vectoring Diptera have aquatic larvae (?)

Megaloptera & Neuroptera

Open tracheal system in flies• Respiratory siphons near abdomen or thorax• Different location in mosquito pupa than larva

How do aquatic insects obtain oxygen?

• Atmospheric oxygen– Keep part of body out of

water– Carry oxygen into water

• Aqueous oxygen– Specialized tracheal

systems

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 diving beetles

• Bubble stored beneath elytra• Gas exchange can occur in water

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• Flattened bodies• Attachment through suckers

Water pennies (Coleoptera: Psephenidae)

Net-winged midges(Diptera: Blephariceridae

More Lotic Adaptations• Nets & Cases

Trichoptera net

Trichoptera cases

Lentic Adaptations• Taking advantage of surface

tension of still water

Water Strider (Gerridae)

Whirligig Beetle (Gyrinidae)

Adaptations to nearly anoxic environments

• Hemoglobins– Many larval chironomid midges (Diptera) = bloodworms– Very, very high affinity for oxygen (unlike us)

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