A Pond Full of Backswimmers

The pond in my backyard is teaming with invertebrates, the most animated of which right now are the backswimmers. Backswimmers (Family Notonectidae) are aquatic predators that have a worldwide distribution and can be found in pools of water, small ponds, and the shallow waters along the edges of lakes.

Adult backswimmers have large, dark reddish-brown eyes and long hind legs that serve as paddles for swimming. Their front and middle pairs of legs are used to catch prey. The upper-side (which faces downward when they are swimming) is pale and has a convex ridge. The under-side (which faces upward when swimming) is usually brown or black.

Backswimmers are easily confused with water boatmen (Family Corixidae). The two types of insect can be distinguished by the orientation of their body in the water. Water boatmen swim right-side up while backswimmers (as their name implies) swim upside-down, on their backs.

The species in my backyard pond is quite likely the common backswimmer (Notonecta glauca). They home in on their prey by sensing vibrations in the water. They also have keen eyesight and are quick to descend downward in the water if they see danger approaching.

Photo © Laura Klappenbach.