Aquatic Insects - Types of Water Insects
Insects are the most diverse animals on the planet, of which more than a million species have been identified. Estimates indicate there is still between six to ten times this amount yet to be discovered. With such a wide distribution and diversity, they have inhabited practically every biome on the planet, including water. If we are to think of insects, we don't normally associate them with being under water. For this reason, AnimalWised presents our list of aquatic insects. We share these types of water insects and present their known behaviors and characteristics. We also provide examples of aquatic insect species with photos so you can see what they look like.
What are aquatic insects?
Aquatic insects, also known as water insects, are types of invertebrate animals which spend at least some of their life cycle in water. Some of these species may only carry out their developmental stages under water while they become exclusively terrestrial once they reach maturity.
Do insects live in the ocean?
When we discuss aquatic insects, we are almost exclusively refer to freshwater insects. Relatively very few marine insects exist. If they do, they tend to live in littoral or intertidal areas near the shore. It is believed that there are not any insects living in the open water because their respiratory system prevents them from diving sufficiently to evade predation.
You can learn about other groups of arthropods in our related article on the types of stick insects.
How do aquatic insects breathe?
All animals need to carry out respiration. They take oxygen from their environment and then distribute it throughout their body. However, not all animals do it in the same way. The process of respiration varies from one group to another due to the various adaptations animals have developed to better interact with their environments.
Generally speaking, insects do not have lungs. Rather, they have holes in some areas of the body that are known as spiracles through which oxygen enters. Air then passes to branched structures called tracheae which then diffuses oxygen to the various tissues.
In the case of aquatic insects, a series of adaptations or peculiarities have been developed to be able to breathe underwater. Water insects can have an open or a closed tracheal system. Depending on which they possess, their method of breathing underwater can vary:
- Open tracheal system system: the respiratory structures necessarily have to come into contact with the air to take in the oxygen.
- Closed tracheal system: the spiracles of the insect do not need to be in contact with the air because they can take oxygen from the water.
In the open tracheal system, aquatic insects can breathe in one of the following ways:
- Through a structure called a siphon: the animal draws from the water to take in air, while the rest of the body is submerged.
- Using villi on the abdomen: they come into contact with the surface air and diffuse oxygen to the spiracles.
- Breaking submerged plant parts: some water insects can breathe by taking accumulated oxygen directly from plant tissue.
- Capture an air bubble: the animals rises to the top to capture an air bubble. This bubble surrounds the insect and they can breathe while inside. When the bubble is about to end or bursts, they repeat the process.
In the case of the closed tracheal system, aquatic insects breathe:
- Through their skin: because the oxygen present in the water enters the animal's body through diffusion to reach all tissues.
- Gills: although we associate them more with fish, some water insects have extensions of tracheal system which reach out to the external tissue. They allow oxygen to be obtained very efficiently.
Characteristics of aquatic insects
Aquatic insects have a series of characteristics to be able to lead a complete or partial life in water, on or around. Among these we can mention:
- Some species have hydrodynamic bodies, making them good divers.
- In certain cases they have modified paddle-shaped hind legs. Some also have the addition of setae, a hair-like appendage which helps to swim.
- There are diving aquatic insects need to go to the surface to breathe. Others are swimmers, so they remain constantly submerged. Others are known as grabbers as they strongly attach themselves to some rocky or vegetable substrate in the water.
- They can be herbivorous, detritivorous or carnivorous animals, depending on their food source.
- As generally happens with non-aquatic insects, they reproduce by means of eggs from which a larva emerges. The larva then undergoes metamorphosis and several other stages to finally form the adult.
- From an ecological point of view they are important for food chains within aquatic ecosystems.
- They have a waxy cuticle in the case of freshwater insects as it protects them by preventing excess water entering the body. However, in submerged respiration, this excess water is regulated by a constant and dilute excretion of liquids.
- Some semi-aquatic insects have the ability to walk on water. They do not break the surface tension of the water and can subsequently be supported by it.
Examples of aquatic insects
As we mentioned at the beginning, insects are a very diverse group within the animal world. It is important to remember that some species live their entire lives in water, while others have a short terrestrial period in their adult form. In these cases, they are also usually considered aquatic, because their greatest development is carried out submerged in water.
Certain examples of aquatic insects are:
- Giant water bugs (Belostomatidae)
- Great silver water beetle (Hydrophilus piceus)
- Predaceous diving beetles (Dytiscidae)
- Microcaddisflies (Hydroptilidae)
- Alkali fly (Ephydra hians)
- Small water striders (Veliidae)
- Whirligig beetles (Gyrinidae)
- Burrowing water beetles (Noteridae)
- Squeak beetles (Hygrobiidae)
- Haliplids or crawling water beetles (Haliplidae)
- Riffle beetles (Elmidae)
- Water boatmen (Corixidae)
- Water striders or pond skaters (Gerridae)
- Backswimmers (Notonectidae)
While some species of ant like places with a lot of moisture, none are considered aquatic insects. Learn more about this different insect species with our article on the different types of ants.
If you want to read similar articles to Aquatic Insects - Types of Water Insects, we recommend you visit our Facts about the animal kingdom category.
1. Maddrell, S. H. P. (1998). Why are there no insects in the open sea? The Journal of Experimental Biology, 201, 2461-2464.
- Hanson, P., Springer, M., & Ramirez, A. (2010). Chapter 1: Introduction to groups of aquatic macroinvertebrates. Journal of Tropical Biology, 58(4), 3-37. http://www.scielo.sa.cr/scielo.php?script=sci_arttext&pid=S0034-77442010000800001&lng=en&tlng=es
- Reynoso, D., & Novelo, R. (2022). Breathing underwater: insects. Eco-logical Magazine. https://www.inecol.mx/inecol/index.php/es/2013-06-05-10-34-10/17-ciencia-hoy/1157-respirar-bajo-el-agua-insectos
- Cheng, L. (2009). Marine Insects. In V. H. Resh & R. T. Cardé (Eds.), Encyclopedia of Insects (pp. 600–604). Academic Press. https://doi.org/10.1016/B978-0-12-374144-8.00167-3