Backswimmers Identification Guide

Backswimmer Identification Guide

Physical Characteristics

Backswimmers are small to medium aquatic insects. They measure between 5 and 17 millimeters long. Their most notable trait is that they swim upside down. Their pale belly faces up toward the water surface. This upside-down swimming gives them their name and makes them easy to spot.

The body of a backswimmer looks like a small boat. Their coloring is the reverse of most water insects. The belly, which faces up as they swim, is pale cream or white. The back, which faces down, is darker brown or spotted. This color pattern helps hide them from predators above and below.

Backswimmers have large eyes that wrap around the sides of their head. These eyes give them great vision for spotting prey. Their back legs are much longer than the others. These legs are flat with tiny hairs and work like oars to push them through water. The front legs are short and used to grab prey.

Common Species

Several backswimmer species live throughout North America. The most common is Notonecta undulata. This species is found across the United States and Canada. Notonecta irrorata is another species often seen, mainly in eastern states. Notonecta kirbyi is common in western North America.

All species swim upside down and have a similar body shape. They vary a bit in size and color. Most backswimmers found in home pools belong to these common species.

Backswimmer Behavior and Biology

Backswimmers are hunters that spend most of their lives in water. They live in ponds, lakes, and slow streams. They also show up in swimming pools, which frustrates many homeowners. They hang just below the water surface with their long back legs spread out, ready to swim.

These insects breathe air. They carry an air bubble along their belly that makes them look silvery underwater. They must come up to the surface now and then to get more air. This air bubble also helps them float. When they stop swimming, they drift upward.

Backswimmers hunt by waiting. They stay still at the surface and feel for vibrations from insects that fall into the water. When they sense prey, they swim fast toward it, grab it with their front legs, and stab it with their sharp beak. They pump in juices that turn the prey’s insides to liquid, then drink it up.

Even though they live in water, backswimmers can fly well. They usually fly at night and use the reflection of moonlight on water to find new places to live. This is why they often show up in pools right after you fill or open them for the season. Lights near pools can also draw them in.

Life Cycle

Backswimmers go through three life stages: egg, nymph, and adult. Females lay eggs on water plants or other surfaces underwater in spring. The eggs hatch into nymphs that look like small adults but do not have full wings yet.

Nymphs molt five times over several weeks before becoming adults. Adults can live for several months. They may spend the winter in deeper water and become active again when it warms up. Most groups produce one to two generations per year based on the climate.

Treatment Approaches for Backswimmers

Backswimmers are a nuisance for pool owners but not true household pests. They do not infest homes or damage property. The goal is to make your pool less appealing to these insects and remove them when they show up.

Here are ways to reduce backswimmers in your pool:

• Remove their food: Backswimmers come to pools because smaller insects fall in and become food. Skim your pool often to clear out debris and dead bugs. Without food, backswimmers have less reason to stay.

• Keep up with pool care: Keep chlorine at the right level and run the filter often. A clean pool draws fewer water insects than a dirty one. Make sure pH levels stay balanced.

• Turn off lights at night: Backswimmers and the bugs they eat are drawn to light. Turn off pool lights when you are not using the pool, especially at night. You can also place lights away from the pool to lure insects elsewhere.

• Scoop them out: Use a pool skimmer or net to remove backswimmers by hand. A pool vacuum works too. This gives quick relief when you see a lot of them.

• Use a pool cover: A cover stops backswimmers from getting in when you are not using the pool. It also keeps other insects out, which cuts off their food supply.

Some algaecides sold for water boatmen may also affect backswimmers. However, scooping them out and changing their habitat usually work better. These methods also avoid adding extra chemicals to your pool.

References

• Backswimmers - University of Kentucky Entomology
• Backswimmers (Notonecta) - iNaturalist
• Backswimmers - Missouri Department of Conservation
• Notonectidae - Wikipedia