Common backswimmer

Systematic position: The common backswimmer (Notonecta undulata) belongs to the order Hemiptera and the family Notonectidae. These insects are well-known predatory water bugs characterized by their unique habit of swimming upside down, using their long, oar-like hind legs to navigate through fresh water.

Affected crops/environments: While not a pest of traditional agricultural crops, this species is a significant pest in the field of aquaculture. It poses a serious threat to fish hatcheries and nurseries, where it predates extensively on fish fry, causing substantial losses to fish production systems.

Biology and life cycle: The species exhibits a life cycle involving incomplete metamorphosis. Adults overwinter in protected areas of ponds or muddy bottoms. In the spring, females lay eggs on aquatic vegetation. The nymphs undergo several molts before reaching maturity, maintaining a strictly predatory diet throughout their entire development.

Nature of damage and harmfulness: The backswimmer is a highly efficient predator equipped with piercing-sucking mouthparts. It injects potent enzymes into its prey to liquefy the internal tissues before consumption. In high densities, these bugs can devastate fish fry populations within a pond, leading to severe economic impacts on commercial fisheries.

Control measures: Management of the backswimmer is focused on physical and environmental modifications of the aquatic environment. Recommended practices include:

• Draining and sanitizing ponds periodically to break the life cycle.
• Managing and removing dense aquatic vegetation that provides shelter for nymphs.
• Installing fine-mesh screens on water supply inlets to prevent adult colonization.
• Regular inspection and manual removal of predatory insects using surface nets.