Water insects 101

[Dryrod]

[font "Poor Richard"][green][size 3]Getting Oxygen While Under Water
Many "aquatic insects" are associated with the water's edge or surface and seldom face the challenges of being submerged and getting oxygen. One of the most common examples of an insect associated with the water surface is the water strider that does not break the water's surface as it skates on top of the water found in streams, rivers, and ponds and, even the ocean! Despite almost never being found away from water, insects that never swim don't face the main problem that the insects below do- Breathing under water.
Some insects act like people in pools, getting air at the surface and then "holding their breath". When their air supply runs out, they must return to the surface. Others use snorkels which allow the insect to remain under water most of its life, as long as it stays close to the water surface. Finally, some insects have become like fish- adapting to obtain dissolved oxygen from the water.
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[size 3][font "Poor Richard"][green]Based on how the insects breathe under water, insects are split into two general categories of respiration: Apneustic and Hydropneustic.
Aeropneustic (Aero = air, pneustic = breath) aquatic insects include the submerged or partially submerged species that breath atmospheric air. Surface breathers include insects that use breathing tubes that are extended above the water surface while the remainder of the insect stays submerged. Common examples of insects that use this method include water scorpions (Hemiptera) and rattailed maggots (a fly). Other insects trap air at the surface and then dive beneath the water surface, carrying an air supply with them. Like a scuba tank, when the stored air is depleted, the insect must return to the surface to re-supply. Common examples of insects using this method include Diving Beetles (Coleoptera) and backswimmers (Hemiptera). A third type of apneustic respiration: endophytic respiration is used by insects which tap into plants and breath atmospheric air through the stems. This unusual strategy is found in a few species of mosquitoes and aquatic leaf beetle larvae.

[/green][/font][font "Times New Roman"][font "Poor Richard"][green]The other major respiratory category, hydropneustic (Hydro = water, pneustic = breath) respiration, is found in insects that obtain their oxygen needs from the water. Since most insects are small, the majority can obtain some oxygen directly across their exoskeleton. This is termed "cuticular respiration" and often insects and their larvae have special areas of their exoskeleton that allow diffusion. But, as insects get larger or move more, diffusion is no longer able to supply enough oxygen. Many insects have special flaps of very thin membranes that extend from their bodies. These membranes are called gills and they increase the surface area and thus, the oxygen supply. The main insect orders (Odonata, Ephemeroptera, Trichoptera, and Plecoptera) that are exclusively aquatic all have gills as larvae.[/green][/font] [/font][/size]
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[font "Poor Richard"][size 3][green]A rattailed maggot
B diving beetle
C mayfly larva
D mosquito larva
E water strider

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