Hydrometra gracilentaHydrometra gracilenta, the lesser water-measurer, is a species of aquatic bugs in the family Hydrometridae.DescriptionHydrometra gracilenta is long, somewhat smaller than Hydrometra stagnorum; its eyes are located halfway down its head. Its specific name is from the Latin word for "slender."HabitatThis species lives in ponds in Northern Europe and Italy. It is on the United Kingdom Biodiversity Action Plan list, preferring well-vegetated ditches flooded, or surface wet fen with dense vegetation.BehaviourIt is diurnal and eats other insects, including Chironomidae. The female lays her eggs in May or June; they develop into nymphs and then become adults by July. The name "water measurer" refers to the insects' habit of walking on the surface of ditches and ponds, apparently pacing the distances between points. Hydrophobic hairs on its legs allow it to walk on the surface of the water.