grousewinged backswimmer

not listed

NNR - Unranked

not listed

Grousewinged backswimmer is a common, relatively large, aquatic, true bug. It occurs throughout the United States and southern Canada except in the Great Basin and in the southeast, where it is mostly absent. It is the most common and widespread backswimmer in the United States. It is common and locally abundant in Minnesota. It is found mostly in ponds, also in lakes, and occasionally in streams and rivers when food is scarce. Its preferred food is mosquito larvae, but it is a generalist feeder and will prey on small crustaceans, dragonfly nymphs, caddisflies, fish eggs, and terrestrial insects that land on or fall on the water surface.

Adults are 7⁄16″ to ½″ (10.5 to 12.6 mm) in length, elongated oval when viewed from above, and convex when viewed from the side. Males and females are alike in size, form, and color.

The head is pale tan or greenish. The front of the head is somewhat rounded when viewed from above. The upper side of the head (vertex) is widest at the front, and narrow at the back, and as long as it is wide in front. The antennae are shorter than the head and have four segments. The third segment is shorter than the fourth. They are usually partly concealed in grooves on the underside of the head. The compound eyes are large and dark red. There are no simple eyes (ocelli).

The front plate on the thorax (pronotum) is less than twice as long as the head. The lateral margins are straight. The color is variable but is usually some shade of tan. It is translucent and the rear half is darkened by the middle plate (scutum) beneath it showing through. The plate between the wing bases (scutellum) is large and black with a variable amount of orange markings. It may be entirely black, black with lateral margins and an orange tip, or almost entirely orange. It is covered with short, golden hairs.

The wing covers (hemelytra) are white with black markings, and are covered with short, golden hairs. They have a thickened leathery section at the base and a thin membranous section at the tip with a clear dividing line between the two. The thickened basal part is comprised of a narrow area (clavus) behind the scutellum when the wings are closed, and the remaining, broad, marginal area (corium). The black markings are highly variable. Generally, there is a black, wavy, transverse band that crosses the tip of the corium and the base of the membrane. Grousewinged backswimmer is the only backswimmer that has this band. Darker individuals have another band in the middle of the corium and a black streak on the outer margin. Lighter individuals have almost no black markings.

The underside of the abdomen is thickly covered with hairs on the sides and in the middle. This forms a pair of “gutters” through which air is transported.

The legs are the same color as the head. The hind legs are very long and are fringed for swimming. The end part of each leg (tarsus), corresponding to the foot, has just two segments. It is not scooped. The end tarsal segment has two claws at the tip, but on the hind legs these are concealed by the fringe.

Total length: 7⁄16″ to ½″ (10.5 to 12.6 mm)

Ponds and lakes

Backswimmers swim upside down. They rest with their body at an angle and their head down, attached to the underside of the film on the water surface. They are good fliers but only fair swimmers. They can deliver a painful bite to humans if handled.

The female attaches an elongated, white egg to submerged objects. There are five nymphal stages (instars). Adults overwinter.

Mosquito larvae, small crustaceans, dragonfly nymphs, caddisflies, fish eggs, and terrestrial insects

Sources

27, 29, 30, 82, 83.

The genus Notonecta of the world (Notonectidae-Hemiptera). Hungerford, H.B. 1934. The University of Kansas Science Bulletin 21(1):5-195.

Common and widespread

The highly variable markings on the hemelytra follow several distinct patterns. This has given rise to numerous varieties being named. However, the patterns are linked by intermediate forms, and entomologists no longer recognize any varieties.

Location: north Minneapolis

Hello. I was on your website after identifying what appears to be a grousewinged backswimmer (notonecta undulata) in north Minneapolis. I did not have a camera/phone handy, but it was unmistakably mostly white, about a cm or more in length, with a black triangular shape on the back.

We thought it was a moth because we saw it scooting around a puddle and then flying. It kept landing in the puddle so we went to help it out. That's when we saw that it was more of a water beetle and had the look of a water boatman, with the "paddle" arms splayed out to the sides.

I don't know how common these are in Minnesota, but it was my first time seeing one, and not seeing it on your Hemiptera list made me curious! I was unable to find out this bug's range online.