Water scorpion
Nepa cinerea
The water scorpion is a flat-bodied aquatic bug characterized by its leaf-like shape and a long breathing tube (siphon) at the end of its abdomen. It prefers shallow, stagnant, or slow-moving waters with dense vegetation or leaf litter. Despite its name and raptorial forelegs, it is not a scorpion but a member of the Hemiptera order. It is a specialized ambush predator that remains motionless and perfectly camouflaged while waiting for prey.
Details
Identification
Leaf-like flat body; grey-brown to black-brown coloration; forelegs modified into raptorial legs; approx. 1 cm long respiratory siphon.
Social behavior
Solitary; exhibits cannibalistic behavior at high densities or when food is scarce.
Diet
Carnivorous; feeds on insect larvae, small crustaceans, tadpoles, and occasionally small fish.
Hunting strategy
Ambush predator; waits motionlessly for prey and seizes it with raptorial legs before sucking it dry with the rostrum.
Spawning substrate
Eggs are inserted into soft aquatic plant tissue or decaying plant material just below the water surface.
Overwintering
Overwinters as an adult in the mud or under aquatic plants at the bottom of the water body.
Ecology
Ecological role
Important predator in the macrozoobenthos; regulates populations of smaller invertebrates and is prey for larger animals.
Natural predators
Larger fish, predatory beetle larvae (e.g., great diving beetles), and various waterfowl.
Competitor species
Other predatory aquatic bugs such as backswimmers (Notonecta) or water stick insects (Ranatra linearis).
Ecosystem service
Contributes to maintaining the ecological balance in small water bodies.
Threats
Destruction of riparian vegetation, drainage of ponds, pesticide pollution, and eutrophication.
Scientific profile
Profile
Distinguishing features
Flat, leaf-shaped body; forelegs modified into raptorial legs; long, single respiratory tube (siphon) at the end of the abdomen, which can nearly reach the body length.
Role in food web
Secondary consumer and significant predator in the littoral zone; regulates the density of smaller invertebrates.
Protection & threats
Main threats
Loss of small water bodies, destruction of riparian vegetation due to construction, excessive fish stocking, and pesticide input from agriculture.
Population trend
Stable; the species is widespread in Central Europe and common in suitable habitats.
Conservation measures
Preservation and creation of small water bodies, protection of reed beds, and avoidance of intensive fishery use in shallow water zones.