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Insects and other arthropods

Aquatic insects

Aquatic insects may be found in any container which collects enough standing water for their survival: temporary puddles, bird baths and cavities in trees are a few examples of suitable locations.
Photo: Insectarium de Montréal (Jacques de Tonnancour)
Dytiscidae, Québec, Canada.
  • Dytiscidae, Québec, Canada.
  • Mesovelia sp., Québec, Canada.
  • Erythemis mithroides, Mexico.
  • Notonectidae, Québec, Canada.

Most aquatic insects, including dragonflies, diving beetles and caddisflies, live in fresh water. In this environment, their number and diversity are 12 times greater than other animals that share the same habitat, including fish, amphibians and crustaceans. Very few insects live in salt water. The most common salt water dwellers are insects that look like water striders, called halobates or sea skaters, which “surf” the waves of the ocean!

Most aquatic insects live in shallow water near shorelines, where light is still visible from the bottom. They live in all kinds of places, from mountain streams and rivers to lakes and tranquil ponds. The more rich in nutrients the habitat is, the greater the diversity of insects that live there.

Ecological roles

In fresh water, larvae filter water and decompose it organically. They are at the bottom of the food chain and support a great diversity of aquatic animals by serving as a food source. Many adults are predators of other insects. The presence of insects in a body of water is a good indicator of the health of the living environment.

Insects that live part of their lives in the water

The eggs, larvae and often the nymphs of many aquatic insect species develop in the water. The pupae then leave the water so that they can fly away as adults. The pupae and adults feed in different environments, which reduces competition between them. For example, adult dragonflies are land predators and do not hunt the same prey as their offspring in the water. Others, such as mayflies and dobsonflies, accumulate energy in the larval stages. Once they reach adulthood, they no longer eat – they just reproduce on land!

Insects that live their whole lives in the water

Many species of insects spend their whole lives in the water. For some of them, the eggs, larvae and pupae develop in the water, while others live in mud along the shoreline. In all cases, the adults maintain an aquatic lifestyle. At this stage, many are active both in the air and in the water. To find new food resources or lay eggs, adult giant water bugs fly from one body of water to another.

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