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Backswimmers

Notonectidae (about 32 North American species)[3]

Backswimmers are slender, predatory water bugs that swim on their backs; they fly to lights at night and often end up in swimming pools, and unlike water boatmen they can deliver a painful bite if handled.[1][2]

Group
Insect
Order
Hemiptera
Family
Notonectidae
US records
50 states
Sources
3 cited
Updated
2026-10-17
Backswimmer, a slender water bug with long oar-like hind legs, at the water's edge
Backswimmer, a slender water bug with long oar-like hind legs, at the water's edge. Photo: Neil Clark, public domain (CC0), via iNaturalist
On this page
  1. Identification
  2. Look-alikes
  3. Where it lives
  4. Biology
  5. Damage and signs
  6. Health risk
  7. Control
  8. Related profiles
  9. Common questions
  10. Sources

How to identify it

  • Adults are usually less than 1/2 inch long, slender and streamlined, with a keeled back like the bottom of a boat and long, oar-like, hair-fringed hind legs.[1]
  • They swim belly-up and rest at the water surface tilted head-down, with the tip of the abdomen poking out.[1]

Look-alikes

Look-alikeHow to tell them apart
Water boatmenWater boatmen swim right side up, have flatter, usually darker bodies with fine parallel crosslines on the back, and don't prey on animals or bite.[1]

Where it lives

About 32 species occur in North America, in ponds and quiet areas of lakes and streams.[1][2]

US map: public records from 50 states since 1990 (GBIF).

Biology and life cycle

They lie in wait for prey such as other aquatic insects, tadpoles and small fish, then lunge and inject saliva that subdues the prey and begins digesting it; backswimmers also eat mosquito larvae.[1][2]

Females glue elongated eggs to the stems of submerged plants, and the young look like small wingless adults.[1]

Damage and signs

  • Adults fly to artificial lights at night and are clumsy out of water, so they often land in swimming pools after a night's flight.[1]

Health risk

Backswimmers can deliver a painful bite if mishandled or pressed against skin, so take care handling them.[1]

Control

Keep them out

Because they are drawn to lights at night, lighting near a pool can draw more of them in.[1]

Traps and physical control

Scoop them out of pools with a skimmer rather than by hand, since they can bite.[1]

Common questions

What bit me in the swimming pool?
A sharp, painful bite while swimming, especially after pool lights were on overnight, is often a backswimmer, a water bug that swims upside down.[1]
How do I tell backswimmers from water boatmen?
Backswimmers swim upside down and have a keeled back without crosslines; water boatmen swim right side up, have fine parallel lines on the back and don't bite.[1]

Sources

  1. Missouri Department of Conservation, “Backswimmers (field guide).” mdc.mo.gov/discover-nature/field-guide/backswimmers (accessed 2026-10-17)
  2. UF/IFAS Extension (EDIS), “Common Backswimmer, Notonecta glauca (Featured Creatures, EENY-738).” edis.ifas.ufl.edu/publication/IN1262 (accessed 2026-10-17)
  3. iNaturalist, “Notonectidae taxon page (order and family).” www.inaturalist.org/taxa/56556 (accessed 2026-10-06)

Updated 2026-10-17. Built from sourced records. Spot an error? Tell us.