Water beetles are one of the most diverse groups in freshwater – in Britain there are around 350 species – but because they are the Little Brown Jobs of the freshwater world many people don’t realise quite how many different types there are.
The picture shows what is one of the commonest water beetles the Common Black Diving Beetle, Agabus bipustulatus, which is about 1 cm long.
In a good wildlife pond there should be lots of different kinds of water beetles. Between a third and a half of all the species of animals you can see will be water beetles. In running waters there will be fewer species, but they should always be present.
Many water beetles are great fliers. They quickly colonise new ponds, and also move between ponds and other freshwaters during the year.
But not all beetles are fast movers: some can’t fly at all, or only when its unusually warm – so can’t easily move from one pond to another. These species are often some of the most endangered because if the place they are living becomes in some way unsuitable they can’t move to a new home.
Don’t forget to look out for water beetle larvae too. Many look a bit like the larvae of alderflies but often have two tails, and they lack the gills along the side of the body that are one of the distinguishing features of alderfly larvae.