Water scorpion

The Water scorpion (Nepa rubra, also commonly known as Nepa cinerea) is a member of the order Hemiptera and the family Nepidae. Unlike many other insects labeled as agricultural pests, this species is a strictly predatory aquatic insect that does not feed on crops or terrestrial plants.

The primary agricultural impact of Nepa rubra is restricted to the aquaculture sector. It is considered a nuisance in commercial fish farms and ornamental ponds because it preys on fish fry, tadpoles, and other beneficial aquatic organisms. Their presence can significantly reduce the survival rate of newly hatched fish in artificial tanks.

The life cycle of the water scorpion is semi-aquatic. Females lay their eggs within the tissues of emergent aquatic plants. After hatching, the nymphs undergo incomplete metamorphosis, passing through several stages of growth. Both adults and nymphs are well-adapted to aquatic life, utilizing a long terminal respiratory siphon to breathe air from the surface.

The damage caused by this insect is defined by its predatory nature. It waits motionless in the substrate or vegetation for its prey to swim by, then strikes with its raptorial forelegs. For humans, these insects can inflict a painful bite if handled, so caution is advised when working with water sources inhabited by these creatures.

Integrated management practices to control their presence include:

• Regular maintenance of ponds, including the removal of dense marginal vegetation where they lay eggs.
• Mechanical barriers and netting to protect hatcheries from adult migration.
• Frequent water quality monitoring to prevent conditions that favor high populations of aquatic insects.
• Periodic drainage of ponds to eliminate the habitat of larvae and adult populations.