Contained families:
Nepidae (water scorpions, needle bugs or water stick insects)
Notonectidae (backswimmers)
Corixidae (water boatmen)
Naucoridae (saucer bug or creeping water bug)
Gerridae (water striders or pond skaters)
Hydrometridae (water measurers)

Water scorpions – Nepa cinerea
(order Hemiptera, family Nepidae, subfamily Nepinae)

Feeding:
Piercer-predators using segmented beak to pierce their prey and suck the fluids.

Habitat:
Water scorpions occur in a variety of wetlands, ponds and by the edges of slow flowing waters.

Movement:
They climb among aquatic vegetation or slowly walk near the surface.

Size:
Adults can grow up to sizes around 40 mm (not including breathing tubes).

Life cycle:
Water scorpions undergo incomplete metamorphosis. Their life cycle includes three stages – egg, nymph (which looks like a small adult) and adult. Most species produce 1 or 2 generations per year.

Introduction:
A common feature of the order Hemiptera is the elongated beak (modified mouthparts) that projects from the head. When not feeding, it is mostly composed under the head.

Water scorpions have a broad and distinctly flattened body and three pairs of long segmented legs. First pair is raptorial, second and third pairs of legs end with two tarsal claws which are used to hold on vegetation.

They use a snorkel-like tube (siphon) at the end of the abdomen to reach atmospheric oxygen for breathing. Front wings are partially modified into hardened covering of the second membranous wings. When nepids submerge deeper into the water, they trap the air supply under this covering.

Water scorpions move slowly and do not change their position often. They are covered in a layer of sediments and algae or even colonized by other microorganisms. Lack of movement causes that some insects and snails may lay eggs on them. Colour ranging from brown to grey and leaf-like body shape make them perfectly camouflaged in accumulations of dead leaves and tangles of aquatic vegetation.

Water scorpions have well developed eyesight allowing them to ambush fast moving animals. When the unsuspecting victim occurs nearby, they quickly grab and immobilize it by the front pair of raptorial legs (in the same way like praying mantises). From the grip resembling a closing mechanism of the clasp-knife is very difficult to escape.

Among other aquatic invertebrates, their prey can include small fish, tadpoles and terrestrial insects that get stuck on the water surface. Nymphs undergo several molts before reaching fully adult stage.

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Needle bugs or water stick insects – Ranatra linearis
(order Hemiptera, family Nepidae, subfamily Ranatrinae)

Feeding:
Piercer-predators using a segmented beak to pierce their prey and suck the fluids.

Habitat:
Water scorpions occur in a variety of wetlands, ponds and by the edges of slow flowing waters.

Movement:
They climb among the vegetation or slowly walk near the surface.

Size:
Adults can grow up to sizes around 45 mm (not including breathing tubes).

Life cycle:
Needle bugs undergo incomplete metamorphosis. Their life cycle includes three stages – egg, nymph (which looks like small adult) and adult. Most species produce 1 or 2 generations per year.

Other characteristics:
Needle bugs are closely related to water scorpions and share almost all their characteristics. The most obvious difference is a long, slender and almost cylindrical body resembling a twig (in contrast to the leaf-like body shape of water scorpions).

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Backswimmers
(order Hemiptera, family Notonectidae)

Feeding:
Piercer-predators using a segmented beak to pierce their prey and suck the fluids.

Habitat:
Backswimmers inhabit a variety of wetlands, ponds and slow sections of flowing waters.

Movement:
Swimmers using hind legs as oars.

Size:
Adults can grow up to sizes around 20 mm

Life cycle:
Backswimmers undergo incomplete metamorphosis. Their life cycle includes three stages – egg, nymph (which looks like small adult) and adult. If conditions permit, backswimmers produce several generations per year.

Introduction:
As their common name suggests, backswimmers perform an unusual behavior of swimming upside down on their backs. Coloring is reversed as like position of the body. The top is light, which makes the animal less recognizable against the sky. Bottom is usually dark and backswimmers blend in with the background from the top view. Backswimmers spend most of the time just under the surface, or hide among aquatic vegetation.

They have a streamlined body with distinctly convex top and flattened bottom. Well developed eyes cover a large part of the head and are usually red coloured. Short antennae are concealed under the eyes. The hind pair of legs is elongated and equipped with swimming hairs (forming strong oars), which propel them through the water. Front and middle pairs of legs end with small claws.

Backswimmers breathe atmospheric oxygen from the surface through a row of hair fringes on the end of the body. These hair fringes break the water tension and pierce the surface. The air is stored under the wings and in small hairs on the bottom of the body.

Backswimmers have a segmented beak to pierce their prey and suck the fluids. When not feeding, the beak is composed under the head. Due to upside down position and grasping legs are backswimmers perfectly adapted to hunt insects that get stuck on the water surface. However, some species stalk their prey and hunt in the water column. They feed on insects (cannibalism is no exception), crustaceans and other small animals.

Males often make a sound (stridulate) in order to attract females. Shrill noise is made by rubbing together with specialized body structures equipped with rows of small ridges. Backswimmers rub their front legs against the base of the beak.

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Water boatmen
(order Hemiptera, family Corixidae)

Feeding:
Collectors/gatherers/piercers.

Habitat:
Water boatmen inhabit a variety of wetlands, ponds and slow sections of flowing waters.

Movement:
Swimmers using hind legs as oars. When not swimming, water boatmen occur among aquatic vegetation or at the bottom of shallow waters.

Size:
Adults can grow up to sizes around 15 mm.

Life cycle:
Water boatmen undergo incomplete metamorphosis. Their life cycle includes three stages – egg, nymph (which looks like small adult) and adult. If conditions permit, water boatmen produce several generations per year.

Introduction:
The streamlined body is slightly flattened on the top. Well developed eyes conceal short antennae. Hardened (mostly yellowish) forewings carry various striped and mottled patterns. Mouthparts are modified into a short, broad and triangular beak without visible segments.

The middle pair of legs is equipped with two long claws, which are used to hold onto some object in order to stay under the water (otherwise rise like a buoy).

Front legs end in scoop-like segments lined with hairs. Using this modification, water boatmen continuously stir up fine sediments. The cone beak possesses a small mouth opening at the end, through which they ingest an organic material or suck the fluids. They feed mostly on detritus, algae and plant juices. However, some species feed on other small invertebrates as well.

Corixids breathe atmospheric oxygen and carry a temporary air supply in the form of bubble, which is stored under the wings and around the abdomen. This shiny air supply acts as a physical gill, allowing the insects to extract oxygen from the water and permitting them to venture deeper into the habitat.

Water boatmen stay submerged for quite a long time, thereby avoiding competition with larger predaceous Hemipterans, such as backswimmers or water scorpions.

Males often stridulate by rubbing front legs across the sharp edges of their head. Relating to the body size, one tiny water boatman Micronecta scholtzi makes probably the loudest recorded sound on the planet. Its entire body is only 2 mm long and the “love song” is produced by rubbing their penis across the series of ridges on their belly.

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Saucer bug or creeping water bug
(order Hemiptera, family Naucoridae)

Feeding:
Piercer-predators using segmented beak to pierce their prey and suck the fluids. Naucorids are active and voracious hunters feeding on other invertebrates.

Habitat:
Saucer bugs inhabit variety of wetlands, ponds, lakes and slow sections of flowing waters.

Movement:
Swimmers/crawlers/climbers – Saucer bugs use middle and hind pairs of hairy legs to propel themselves through the water. Some species crawl at the bottom or climb among aquatic vegetation, where search for prey.

Size:
Adults grow up to sizes around 10 mm.

Life cycle:
Saucer bugs undergo incomplete metamorphosis. Their life cycle includes three stages – egg, nymph and adult. Nymphs look like small adults with the exception of developed wings and reproductive organs. Most species produce one generation per year.

Other characteristics:
flattened from top to bottom; head does not protrude out of the oval-shaped body; colour ranges from yellow, green to brown; mottled patterns on the top usually present; front raptorial legs for grasping and holding prey; can inflict painful bite if handled carelessly

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Water striders or pond skaters
(order Hemiptera, family Gerridae)

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Water measurers
(order Hemiptera, family Hydrometridae)

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