Aquatic insects: what they are, types, function and examples

Aquatic insects are those that spend some time in their life cycle, or even their entire life, in water. They are dependent on the aquatic environment, which means that they require it to feed, breathe or reproduce. Let’s review below what characteristics and adaptations they present.

In order to live in water, aquatic insects require particular characteristics that we know as adaptations.

Breathing

Insects need to obtain oxygen, but it is a challenge to achieve it underwater. How do aquatic insects breathe? They have the following ways:

• Presence of plastron, which is a mat-like structure that holds atmospheric oxygen near the spiracles, which are body openings through which air passes. This is water repellent and thus allows air to hold.
• A very thin external tissue that allows oxygen to pass into the circulatory system.
• Presence of siphons, which are similar to snorkel tubes, where insects place them out of the water to breathe while submerged.
• Use of air bubbles, which trap different parts of the body to use as an oxygen tank.
• Presence of tracheobranchs or abdominal gills.

Locomotion

In order to move in the water, there are different strategies that these aquatic insects can use, such as:

• I swim with my legs: they may have many setae or villi that they use to move more easily, or they may be shaped like fins.
• Flotation: They combine with a water-repellent external texture that helps them float without much effort.
• Suspension on water: where they use surface tension to stay suspended without sinking.

Behavior

There are also behavioral adaptations that give these insects advantages in the aquatic environment, such as:

• Handle in groups, because this way you mislead aquatic predators by seeing yourself as a large unit and not small individuals. Furthermore, when they are in a group they navigate the currents better.
• Location in calm water tributaries to avoid being swept away.

There are several types of aquatic insects and different families. It is estimated that there are around 76,000 species of aquatic insects, which represents approximately 8% of the total known insects. We can find beetles, diptera such as mosquitoes, dragonflies, mayflies, among others that we are not so familiar with. Below, we present 10 different water insects and their peculiarities.

Within public health campaigns, much awareness is raised about the importance of not having stagnant water in homes, and this is the medium that mosquitoes that transmit multiple diseases use to lay their larvae. Also known as little nails because they look like them, they are usually seen rising and falling constantly, and this is because they need to come out for air. To do this, they expose a siphon at the end of their body. After the larva stage, they no longer depend on water except to lay eggs again.

They are called that because they have the first pair of legs modified into pincers similar to those of scorpions, and a caudal structure similar to the tail. But the latter is not really a stinger, but rather a siphon that they use to breathe underwater. You may wonder if they are dangerous: they have no venom, but they can bite hard.

These are characteristic insects because they skate on the water. They achieve this with very long and thin legs that, having a small area, do not sink. They are opportunistic predators, feeding on other insects that fall on the surface of the water, and thanks to their specialized legs they can move very quickly to capture their prey.

Find out more about the Water Shoe Rack.

These aquatic insects float on top of the water, but if they feel threatened, they can swim skillfully and in circles, which is why they are known as spinner beetles. They have peculiar adaptations, such as two pairs of divided eyes, with which they can see out of the water, and they can also see below themselves to be alert for predators.

Dragonflies are predators of aquatic insects and always live related to this environment. They even require it because their larvae are aquatic and spend most of their development underwater. These larvae are voracious and feed on small aquatic invertebrates, such as mosquito larvae and tiny crustaceans. When they reach maturity, they emerge from the water to transform into winged adults, thus completing their life cycle.

You may be interested in knowing the red Dragonfly or Sympetrum striolatum.

Unlike the previous ones, these beetles do have swimming underwater as their main movement. They are river insects, that is, freshwater insects. They need to come to the surface to take in air, which they store under their elytra, the typical beetle structures that protect the wings. Then, they submerge again and continue their activity underwater.

They are insects that are relatives of bed bugs, and the adults live completely submerged. They are mainly aquatic feeders, feeding on algae, detritus and small invertebrates. They have a flattened body and legs adapted for swimming, which allows them to move with agility under the surface.

They are close relatives to the boatmen and very similar, but the substantial difference lies in the fact that they swim face up, and in their diet, which is predatory. Although they are skilled swimmers, they can also fly to search for new bodies of water.

These are insects that live up to their name: they live only a few hours or at most a day when they are adults. Its predominant stage is the nymph, which is completely aquatic. They have tracheobranchs, which leave the body to breathe underwater, especially near the substrate.

Also called hydrophilids, these beetles are aquatic and are dedicated to searching for carrion, which they complement with vegetation and even larvae. They have a robust body and hind legs adapted for swimming, which allows them to move easily underwater. Additionally, some can trap air bubbles under their elytra to breathe while remaining submerged.

Aquatic insects feed on different foods, depending on their species. We can find:

• Predators: Most aquatic insects are predators and hunt small fish, tadpoles, or other insects. These generally inject enzymes into their prey to make their interior liquid so they can consume them.
• Herbivores: they feed on aquatic plants and algae.
• Omnivores: are those that are small, like larvae, and that absorb what they can from water that contains zooplankton and phytoplankton.
• Opportunists: they are those who feed on what is available, without preferences.
• Scavengers: There are some insects that feed on dead animals, which is useful for keeping waters clean.
• Cannibals: finally, there are some insects that can feed on the same species. This generally happens with large communities.

Aquatic insects are part of the food chain. They consume organisms, and there are other animals that feed on them, thus allowing a balance in the abundance of biodiversity. Likewise, predators are important for removing mosquito larvae.

On the other hand, aquatic insects are important because they keep the water clean, especially those that are scavengers and remove dead animals to reintegrate them into the food chain.

Finally, aquatic insects function as bioindicators of habitats in good condition, as they are preferred over disturbed places.

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