Invertebrates

Water Scorpion

Nepidae · also called water scorpion, water stick insect

Least Concern → carnivore Rivers & wetlands

A water scorpion is a pond ambush predator that has borrowed a scorpion’s look without any of the hardware. The flat body and the folding, pincer-like front legs are for grabbing prey; the thin “tail” is not a stinger at all but a breathing snorkel. It has no venom in the tail and cannot sting.

Overview

Water scorpions are the true-bug family Nepidae, several hundred species in still, weedy fresh water worldwide. They are sit-and-wait predators that seize insects, water fleas, tadpoles, and small fish with mantis-like folding front legs, pierce them with a short beak, and suck them dry.

The snorkel tail

The long rear projection is a breathing tube — two grooved filaments that lock into a channel. The bug hangs just under the surface with only the tip breaking the film, drawing air while the rest of it stays hidden, so it can ambush motionless for long periods.

Leaves and sticks

The family comes in two shapes: broad, flat, leaf-like water scorpions (Nepa) that drift like dead foliage, and long, thin, twig-like water stick insects (Ranatra) that hang among submerged stems, nearly invisible. Both are poor swimmers that mostly walk. Threatened out of water, a water scorpion plays dead, and it can jab a handler with its beak — a brief sting, nothing more.

Status

Least Concern — common, widespread, and quick to colonise new ponds by flight, though reduced locally by wetland drainage and pesticide runoff. More often overlooked than rare.

Water Scorpion: common questions

Can a water scorpion sting me?

No. The thin tail that gives the water scorpion its name is a hollow breathing tube, not a stinger, and there is no venom gland in it. The bug can, however, jab with the short piercing beak on the underside of its head if it is picked up, and that jab feels like a brief sharp sting or pinprick, sometimes with a little swelling, because the same saliva it uses to subdue prey is mildly irritating. It is harmless and fades in minutes to an hour, and a water scorpion left alone will not attack.

Why does a water scorpion have a long tail?

To breathe without surfacing its body. A water scorpion cannot extract oxygen from water and must get air from above, and rather than swimming up and exposing itself, it hangs just below the surface with only the tip of the tail-tube breaking the film, drawing air down the channel formed by two interlocking filaments into its air-tubes. This lets the bug stay hidden and motionless in ambush for long periods, with the breathing tube acting like a diver's snorkel.

What is a water stick insect?

It is a water scorpion, specifically one of the long, thin, twig-like members of the family such as Ranatra. Instead of the flat leaf shape of the more familiar Nepa water scorpion, a water stick insect has an extremely elongated body and legs and, with its breathing tube, can be over ten centimetres long yet only a few millimetres thick. It hangs vertically or at an angle among submerged plant stems, perfectly camouflaged, and ambushes passing prey with its folding front legs. It is not related to the terrestrial stick insects.

Are water scorpions good or bad for a pond?

They are a natural part of a healthy pond and are neither pest nor benefactor in any strong sense. As predators they help keep populations of mosquito larvae, water fleas, and other small animals in check, and they are food in turn for fish and birds. In a small pond stocked with prized fish fry they could take a few, but they are slow, sit-and-wait hunters rather than active marauders, and their numbers are usually modest. Finding one is generally a sign that the pond has enough cover and prey to support a range of wildlife.

Sources & further reading

Written by HideShark Editorial Team · reviewed by HideShark Science Desk. Published September 11, 2026. Last updated September 11, 2026.

Quick facts

Scientific name: Nepidae
Diet: An ambush predator of other aquatic animals, seizing insects, water fleas, tadpoles, small fish, and other invertebrates with its front legs, piercing them with a short sharp beak, injecting saliva that paralyses and digests, and sucking out the liquefied contents
The tail is a snorkel: The long slender projection at the rear is not a stinger but a breathing tube, made of two grooved filaments that lock together to form a channel, which the bug raises to the surface film to draw air into its air-tubes while the rest of it stays hidden underwater
Not a scorpion: The resemblance to a scorpion, a flat body, grasping front limbs held like pincers, and a thin tail, is entirely superficial, and the water scorpion has no venom gland in the tail, cannot sting, and belongs to the true bugs, not the arachnids
Two body plans: The family contains broad, flat, leaf-shaped water scorpions such as Nepa, which look like a drifting dead leaf, and long, thin, twig-like forms such as Ranatra, the water stick insects, which hang motionless among submerged stems and are almost impossible to pick out
A poor swimmer: Water scorpions swim weakly or not at all and instead walk slowly over the bottom and through vegetation, or hang still near the surface with the breathing tube up, relying on camouflage and ambush rather than pursuit, so they are usually found in shallow, weedy, still water
Playing dead: Handled or threatened out of water, a water scorpion often goes completely rigid and motionless, legs folded, looking like a scrap of dead plant, and it can also give a person a sharp jab with its beak that stings briefly but does no lasting harm
Air-filled eggs: The female lays her eggs in plant stems, mud, or debris at the water's edge, and each egg bears a crown of thin filaments that project into the air and act as gills, drawing oxygen to the developing embryo in the waterlogged surroundings
Range: Still and slow fresh water almost worldwide except the coldest regions, in the shallow, densely vegetated margins of ponds, lakes, marshes, swamps, ditches, canals, rice paddies, and slow streams, among submerged and emergent plants, leaf litter, and debris, usually within reach of the surface so the breathing tube can be raised into the air.
Conservation status: Least Concern → ≈ Water scorpions are common and widespread through much of the world in still fresh water and are not of conservation concern as a group, with several hundred species across the tropics and temperate zones. They can be locally abundant in weedy ponds, ditches, and marsh edges, and they colonise new water bodies as flying adults. Like other freshwater insects they are reduced by the draining and pollution of shallow wetlands and by pesticide and fertiliser runoff, and a few species with narrow ranges could be affected by habitat loss, but the family overall is secure and often overlooked rather than rare in the wild