This insect is a European water measurer (Hydrometra stagnorum), also known as a marsh-treader. They belong to the family Hydrometridae, which consists of all water measurers. These species live on the surface film of water—like pond skaters—but they move in a creeping, stealthy way that allows them to sneak up on their prey. Water measurers are predators at all stages of their lives, using their sharp mouth-parts to spear and suck the life juices out of their prey, which they prefer to be already dead or dying. They use vibrations along the surface of the water to locate their prey, such as the springtail (class Collembola) that the water measurer shown has caught.