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Aquatic insects orwater insects live some portion of theirlife cycle in the water. They feed in the same ways as otherinsects. Somediving insects, such aspredatorydiving beetles, can hunt for food underwater where land-living insects cannotcompete.
Aquatic insects must getoxygen while they are under water.Almost all animals require a source of oxygen to live. Insects draw air into their bodies throughspiracles, holes found along the sides of theabdomen. These spiracles are connected totracheal tubes where oxygen can be absorbed. All aquatic insects have become adapted to their environment with the specialization of these structures, enabling:
The nymphs of thehemimetabolous orders mayflies, dragonflies and stoneflies, and the larvae of theholometabolous ordersmegalopterans and caddisflies, possess tracheal gills, which are outgrowths of the body wall containing a dense network of tracheae covered by a thin cuticle through which oxygen in the water can diffuse.[3][4][5]
Some insects have densely packed hairs (setae) around the spiracles that allow air to remain near, while keeping water away from, the body. The trachea open through spiracles into this air film, allowing access to oxygen. In many such cases, when the insect dives into the water, it carries a layer of air over parts of its surface, and breathes using this trapped air bubble until it is depleted, then returns to the surface to repeat the process. Other types of insects have aplastron or physical gill that can be various combinations of hairs, scales, and undulations projecting from the cuticle, which hold a thin layer of air along the outer surface of the body. In these insects, the volume of the film is small enough, and their respiration slow enough, thatdiffusion from the surrounding water is enough to replenish the oxygen in the pocket of air as fast as it is used. The large proportion ofnitrogen in the air dissolves in water slowly and maintains the gas volume, supporting oxygen diffusion. Insects of this type only rarely need to replenish their supply of air.[6]
Other aquatic insects can remain under water for long periods due to high concentrations of hemoglobin in their hemolymph circulating freely within their body. Hemoglobin bonds strongly to oxygen molecules.[7]
A few insects such aswater scorpions andmosquito larvae have breathing tubes ("siphons") with the opening surrounded byhydrofuge hairs, allowing them to breathe without having to leave the water.
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Aquatic insects use different methods of locomotion in water.
EPT insects, anacronym for Ephemeroptera, Plecoptera and Trichoptera (mayflies, stoneflies and caddisflies), are sensitive to pollutants and are used as an indicator of water quality in streams, rivers and lakes.[8]
Aquatic insects live mostly infreshwater habitats, and there are very few marine insect species.[9] The only true examples ofpelagic insects are thesea skaters, which belongs to the order Hemiptera, and there are a few types of insects that live in theintertidal zone, including larvae ofcaddisflies from the familyChathamiidae,[10] the hemipteranAepophilus bonnairei,[11] and a few other taxa.
