Water scorpions have long thin brown bodies that including the tail is about 50 mm in length. The front legs are modified to grasp prey, their arms can fold in such a way that the prey is dragged right to the mandibles. The 4 back legs can propel the insect forward when it is threatened.
Unlike the tail of a real scorpion, the tail of this species is not dangerous. It is merely a pair of straight, flexible siphons that work like a snorkel. Water scorpions, are air-breathing and need to carry a bubble of air between their fore wings and their abdomen when they are underwater.
When the tip of the long tail breaks the surface, the water scorpion’s oxygen supply gets renewed. However, oxygen permeates into the bubble from the surrounding water. In highly oxygenated water with many plants close to the surface, the water scorpion hardly ever has to renew its air bubbler.
Water scorpions usually spend their time hanging onto bottom debris waiting for prey to come by. When prey approaches, the water scorpion will straighten their hind legs which propel them towards their prey which they grasp with their modified forelimbs. Once the prey is firmly grasped, the water scorpion will inject it with digestive enzymes like a spider and suck out the liquefied fluids.
Although they spend the majority of their lives in water, water scorpions can and do fly. On warm days, they have been known to lift off from ponds and fly around on wings that are fully formed.
Male water scorpions produce chirping noises, much like a cricket, to attract females. After mating, the female will lay several eggs attached to aquatic vegetation. The eggs have two anterior horns that penetrate the surface of the water for air, functioning in the same way as the tail does on the adults.
Vancouver Island has a healthy population of water scorpions.