Notonectidae

Definition

A cosmopolitan family of aquatic predatory true bugs (Hemiptera: Nepomorpha) distinguished by their dorsal-ventral swimming posture—swimming supine with the ventral surface upward—hence the common name 'backswimmers'. Members range 0.5–1.5 cm, possess convex, lightly colored dorsa without striations, non-scoop-shaped front tarsi, and fringed hind legs adapted for swimming. The family comprises approximately 350 species in two subfamilies: Notonectinae (seven genera, generally larger) and Anisopinae (four genera). Notonectidae are readily separated from the superficially similar Corixidae (water boatmen) by coloration, leg morphology, and obligate predatory habit.

Etymology

From the type genus Notonecta (Greek nōton 'back' + nēktēs 'swimmer') + -idae (family suffix)

Example

Notonecta glauca, a common Palaearctic backswimmer, hunts mosquito larvae and other small aquatic prey while swimming inverted beneath the water surface, using its oar-like hind legs and buoyant air reserves carried on the ventral body surface.

Synonyms

• backswimmers (common name)

Related Terms

• Corixidae
• Nepomorpha
• Heteroptera
• Hemiptera
• Notonectinae
• Anisopinae
• Notonecta
• pleuston
• predatory aquatic insects

Usage Notes

Notonectidae and Corixidae are frequently confused by non-specialists; the key distinction is swimming posture (supine vs. prone) and feeding ecology (predatory vs. primarily herbivorous/detritivorous). The family is sometimes referenced in water-quality bioassessment due to the sensitivity of backswimmer populations to aquatic pollution and habitat degradation. The term is always capitalized as a family-group name under zoological nomenclature.