Water striders live on ponds and the calm edges of streams. They seem to skate across the water without getting wet. They stay above the water using water tension. Their legs never actually break the surface of the water but literally do skate along on its surface. Like all insects, they have six legs, but they only skate around on their back four. Their front two legs are used to grab prey. They are predators and will snatch an injured dragonfly off the water using its front pair of legs. They only set them down on the water when resting. They don't sit still for long though or they become prey themselves to hungry fish.
