Water scorpions

The biology of Nepidae is characterized by hemimetabolous development. They typically lay their eggs within the tissues of aquatic plants. Upon hatching, the nymphs resemble adults but lack functional wings. Throughout their lifecycle, they remain submerged, utilizing their long siphons to reach the water surface for respiration, which allows them to stay motionless while waiting for prey.

In terms of agricultural impact, water scorpions are primary pests in aquaculture and fish hatcheries. They pose a significant threat to fry and small fish populations, as they hunt by ambush, gripping their prey and injecting digestive enzymes. High densities of these insects in a pond can lead to severe losses in fish production.

While they are not direct pests of terrestrial crops, their presence in irrigation water or hydroponic reservoirs can disrupt the ecosystem. Their predatory nature can kill beneficial organisms that support the nutrient cycle in closed-loop systems, and their movement can occasionally cause mechanical damage to delicate plant root structures.

Effective management and control measures include:

• Routine removal of dense aquatic vegetation to eliminate predator hiding spots.
• Draining and drying of ponds between cycles to destroy eggs deposited in the substrate.
• Installation of fine-mesh screening on water intake pipes to prevent nymph entry.
• Regular monitoring of fish nurseries to identify and mitigate high populations of aquatic predators.