Invertebrates

Backswimmer

Notonectidae · also called backswimmer, water bee, water wasp

Least Concern → carnivore Rivers & wetlands

A backswimmer is a pond insect that does everything upside down. It hangs just beneath the surface film, belly up, watching the sky through the water for something to land, then rows over with its long back legs and drives a needle-like beak into its prey. Pick one up and it will do the same to you — hence its other names, water bee and water wasp.

Overview

Backswimmers are the water-bug family Notonectidae, several hundred species in still fresh water worldwide. They are fierce predators that grab prey with the front legs, stab it with a piercing beak, inject digestive saliva, and suck it dry — taking mosquito larvae, fallen insects, tadpoles, and small fish. They always swim on their backs, propelled by oar-like, hair-fringed hind legs.

Breathing and hunting

A backswimmer breathes air and dives with a silvery bubble trapped against its underside, which doubles as an oxygen store and a physical gill. That trapped air is why it floats belly-up in the first place. Hanging at the surface, it watches both the air above and the water below, and it can shoot out of the pond and fly to new water, often at night.

The bite

The defensive bite is a real bee-sting-level jab — sharp, burning, lasting minutes to an hour. Not dangerous, but a reason to net rather than grab them.

Status

Least Concern — abundant worldwide and among the first insects to colonise any new pond or water trough. In fishless water they are useful mosquito control; in fish ponds they can take fry.

Backswimmer: common questions

Why do backswimmers swim upside down?

It is tied to how they breathe and hunt. A backswimmer carries a store of air on its underside, which makes that side buoyant, so the bug naturally floats belly-up with its back hanging down. Rather than fight this, backswimmers have fully committed to it, and their eyes, legs, and body shape are all arranged for life inverted. Swimming on its back also lets the bug hang just under the surface film and watch upward for insects that land on or fly near the water, which are a big part of its diet, while its pale belly, now facing up, and dark back, now facing down, give it camouflage from both directions.

Do backswimmers bite, and does it hurt?

Yes, a backswimmer will bite in self-defence if you hold one, and the bite is genuinely painful, commonly compared to a bee sting, with sharp pain and burning that can last from several minutes to an hour and sometimes a small swelling. This is why the insects are nicknamed water bee and water wasp. The bite is not dangerous to a healthy person and needs no more than washing and perhaps a cold compress, but it is a good reason to scoop backswimmers into a net or container rather than pick them up with bare fingers.

What is the difference between a backswimmer and a water boatman?

They look similar and are related, but there are clear differences. A backswimmer swims on its back, is a fierce predator with a stabbing beak, bites people, and has a smooth, keeled, boat-shaped back. A water boatman swims the right way up, is mostly a harmless feeder on algae and detritus that it scoops from the bottom, does not bite, and has a flatter, patterned back. If the bug is belly-up and rowing near the surface it is a backswimmer; if it is right-way-up and grubbing on the bottom it is a water boatman.

Are backswimmers good or bad for a garden pond?

Mostly neutral to helpful. Backswimmers are effective predators of mosquito larvae and pupae and of midge larvae, so in a wildlife pond or a water butt without fish they help keep biting insects down. They are a natural part of a healthy pond food web and are eaten in turn by fish, frogs, and birds. The one drawback is that they will eat tadpoles and the fry of fish, so in a pond stocked with prized fish or used to rear amphibians they can take a toll, though rarely enough to matter in an established pond.

Sources & further reading

Written by HideShark Editorial Team · reviewed by HideShark Science Desk. Published September 11, 2026. Last updated September 11, 2026.

Quick facts

Scientific name: Notonectidae
Diet: An active predator that seizes prey with its front legs and stabs it with a sharp beak, injecting saliva that paralyses the victim and dissolves its insides, then sucking out the liquid, taking mosquito larvae and pupae, other insects that fall on the water, tadpoles, tiny fish, and fish fry
It swims on its back: The backswimmer always swims upside down, its boat-shaped back facing the bottom and its belly toward the surface, propelled by long, oar-like, hair-fringed hind legs that beat together in strokes, so it looks and moves like a tiny rowing boat rowed from underneath
It carries its own air supply: A backswimmer breathes air, and when it dives it takes down a silvery film of air trapped against its underside and among channels of fine hairs, which acts as both an oxygen store and a physical gill, drawing dissolved oxygen from the water so the bug can stay under for long periods
Watching both worlds: Hanging at the surface, a backswimmer watches the air above through the water film for insects landing or flying low, while also scanning the water below, and it can launch straight out of the water and fly to a new pond, often at night and sometimes toward artificial light
The painful bite: Backswimmers will jab a person who picks one up, using the same beak they use on prey, and the bite feels like a bee or wasp sting, sharp and burning for a while, which is why they are widely called water bees or water wasps, though they are true bugs and not related to bees
Balanced beneath the film: A backswimmer floats naturally belly-up because of its trapped air, and it holds station just under the surface at a slight nose-down angle, ready to dart in any direction, gripping the surface film or a plant with its shorter front and middle legs while it waits
Both help and nuisance in a pond: Backswimmers can be common enough to matter in a pond, thinning out mosquito larvae and the young of other insects, and in fishless pools and rain tanks they are useful mosquito control, but they will also take the fry of desirable fish and are themselves eaten by fish, birds, and larger water bugs
Range: Still and slow fresh water worldwide except Antarctica, in ponds, lake margins, marshes, ditches, slow streams, temporary pools, rock pools, and artificial water such as troughs, tanks, and swimming pools, from lowlands to mountain lakes, with a few species tolerating brackish coastal water.
Conservation status: Least Concern → ≈ Backswimmers are common and widespread on every continent except Antarctica, with several hundred species, and they are among the first colonists of new ponds, flooded ditches, water troughs, and garden water features, flying in from other waters. None are of conservation concern as a group. Like other freshwater insects they are sensitive to pesticide runoff, and some water managers regard them as a nuisance in fish hatcheries and ornamental ponds because they prey on fry, but populations overall are robust and quick to recover, helped by the adults' ability to fly between water bodies in the wild