Backswimmers look like aliens

The large, bright backswimmer is one of Denmark’s largest aquatic insects. It is common everywhere in Denmark and is easy to recognise by its large eyes - that make it look like an alien, or an astronaut wearing a helmet – its long, oar-like legs, and its strange colouring. True to its name, it swims on its back (although it flies in the normal position), and this has led to some swapping around of its colours. Instead of being light on its underside and dark on the back, it is light on the back (which is facing downwards, just as the belly would normally be) and dark on its belly, which faces up. This is all part of a primitive kind of camouflage which makes the backswimmers more difficult to see when looked at from above or below.

Even though backswimmers are predators, they don’t usually attack humans, but they have short, strong “beaks” which they are very willing to use if necessary - for example, if you squeeze them too hard. In years where there are many backswimmers, it can be a bit uncomfortable going for a swim in a lake, as the insects might attack, like a concentrated underwater mosquito swarm.