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Common Water-measurer

Common Water-measurer ©Mick E. Talbot

Common water-measurer

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Scientific name: Hydrometra stagnorum
Found in ponds and marshes, the fragile look of the Common water-measurer belies its fierce nature. A predator of small insects, it uses the vibrations of the water's surface to locate its prey.

Top facts

Category

Stats

Length: 0.9-1.3cm

Conservation status

Common.

When to see

January to December

About

The Common water-measurer is a long-legged, thin, brown bug that lives on the surface of the water and around the edges of ponds and marshes. A scavenger and a hunter, it feeds on small insects that float to the surface, whether dead or alive. It is very sensitive to vibrations on the surface of the water, using them as a way to locate prey such as mosquito larvae. It spears its prey with its mouthparts and sucks the contents out of the body.

What to look for

Much more fragile-looking than the similar Pond Skater or Water Cricket, the Common water-measurer is more likely to be found on stagnant water or bare mud. It is brownish and has a long, slender body and head, long legs, and long antennae.

Where to find

Widespread.

Habitats

Did you know?

There are two very similar species of water-measurer in the UK: the Common water-measurer and the Lesser water-measurer (Hydrometra gracilenta). The two can be difficult to tell apart; however, the Lesser water-measurer is very rare and only found around the Norfolk Broads. For this reason, the Lesser Water-measurer is classified as a Priority Species under the UK Post-2010 Biodiversity Framework.