Common water-measurer

Common Water-measurer

Common Water-measurer ©Mick E. Talbot

Common water-measurer

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.

Species information


Length: 0.9-1.3cm

Conservation status


When to see

January to December


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.

How to identify

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.



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.

How people can help

The Wildlife Trusts manage many wetland nature reserves for the benefit of the wildlife they support. You can help by supporting your local Trust and becoming a member; you'll find out about exciting wildlife news, events on your doorstep and volunteering opportunities, and will be helping local wildlife along the way.