What lives in the water

Small animals in stagnant waters

The following selection includes typical, mostly biologically particularly interesting representatives that can be seen with the naked eye. Not all are common. Each selection, including this one, is arbitrary to a certain extent.

Typical representatives

Drawings of the following types can be found below.

1. Larva of a dragonfly

(Maid of honor,Aeshna sp.)

Up to 4.5 cm long, torpedo-shaped; large catch mask. Development time, depending on the type, 1–4 years. Lives predatory on the pond floor and in water plants. Breaths with intestinal gills; swimming movement through jerky expulsion of the respiratory water (recoil principle).

2. Larva of a flat-bellied dragonfly

(Flat belly,Libellula depressa)

Up to 2.5 cm long, relatively wide, abdomen flattened. Larval time 1 or 2 years; up to 10 moults. Loves pure and open water that is not overgrown with vegetation. Never stays in aquatic plants, but lives on the bottom of the water, where it often burrows itself halfway; is therefore always dirty, except in short periods of time after a molt.

3. Larva of a dragonfly

(Rush maiden,Lestes sp.)

Up to 3 cm long, very slender, with 3 oar blades at the end of the body. Development time of the rush damsel species 8-10 weeks, other dragonfly species overwinter at least once.

4. Larva of a mayfly larva

(Baëtis sp.)

Up to 10 mm long, slender, with 3 thread-like, hairy tail appendages. Breathing occurs through thin-skinned tracheal gill leaves that sit on both sides of the abdomen. Adult mayflies are airworthy insects that are not related to flies and, depending on the species, only live a few hours, usually 2-3 days, rarely 2-3 weeks.

5. Water strider

(Gerris sp., Water bug in the broader sense)

Length without legs: smaller species 5-9 mm, large species 12-17 mm. The legs are covered with water-repellent hair that prevents sinking into the water. The animals are carried by the surface tension, just like a greased pin that is placed on the water membrane. The middle legs perform powerful rowing movements, which drive the animals forward up to 60 cm with one stroke. The front legs are used to catch prey. Sensitive hair on the lower limbs register vibrations that cause insects to fall into the water.

6. Swimming bug

(Ilyocoris cimicoides, water bug in the narrower sense)

Length: 12-16 mm. In plant-rich waters. Rear legs covered with webbed hair make them excellent swimmers. The muscular forelegs stab all kinds of aquatic animals up to young fish and bring them to the proboscis and proboscis. Sticks the end of the abdomen over the surface of the water to draw air.

7. Water scorpion

(Nepa rubra, water bug in the narrower sense)

Length without breathing tube: 17–22 mm. Deceptively resembles a mud-covered, dead small leaf. Modest swimmer, crawls slowly through the tangle of aquatic plants or lurks motionless on the bottom of the water for insects and the smallest amphibian larvae, which he catches with a lightning-fast strike of the fangs. A special feature next to the catch legs: long, thin breathing tube on the abdomen, which protrudes little out of the water like a snorkel.

8. Stick bug

(Ranatra linearis, water bug in the narrower sense)

Length without breathing tube: 30–40 mm, the breathing tube is about the same length. Imitates a thin twig. Way of life like water scorpion. The eggs are sunk into floating parts of the plant and each carry 2 long, white, thread-shaped breathing tubes. (The eggs of the water scorpion have 6–9 short breathing tubes.)

9. Backstroke

(Notonecta sp., Water bug in the narrower sense)

Length: 13-16 mm. Swims backside down; the wings folded like a roof over the abdomen form the keel. Good swimmer; can also fly fast and persistently (take-off from the mainland, landing directly in the water). Kills prey with the powerful proboscis. Can also sting people painfully, hence the name "water bee". Regularly draws air on the surface of the water by stretching the two breathing openings at the tip of the abdomen out of the water (see illustration).

10. Row bug, water cicada

(Corixa sp., Water bug)

Length: 5-15 mm. Harmless. Digs through the mud with its shovel-shaped front legs and feeds mainly on algae, which it pricks and sucks with its short trunk. Emerges vigorously for the renewal of the air and pierces the water level with the front legs for split seconds. Also takes off from the water for a flight. The male chirps underwater by stroking the fore legs over the grooved edge of the trunk. So attracts females.

11. Yellow beetle larva

(Dytiscus marginalis)

Mostly hangs lurking on the surface of the water and grabs, paralyzes and kills the prey with the sickle-shaped upper jaw forceps. The injected, brown liquid transforms muscles and intestines after a short time into a thin broth that is absorbed through the jaw canals.

Yellow fire beetle

(Dytiscus marginalis)

30–35 mm long, males have smooth winglets, females grooved lengthways. Looks for food either by swimming around briskly or by "digging". Only eats animal food, aquatic insects and their larvae, tadpoles, newts, snails, worms and carrion. Regularly refuel air on the surface of the water by letting it flow under the wing covers. Flies very well, even at night.

12. Small swimming beetle

(from the family Dytiscidae)

Several species of small and tiny water beetles live in stagnant water and are difficult to identify.

13. Caddisfly larva

(Order Trichoptera, ~ 300 kinds; no flies!)

Larva builds quivers that protect their soft abdomen with tracheal gills. Depending on the type, all kinds of foreign material sticks to the tube that is initially spun: parts of plants, stones, small empty snail shells. Extends the quiver after 5–6 moults at the front end. Construction methods and materials are more or less species-specific (mainly plant parts in stagnant waters).

14. Mosquito larva and pupa

(Culex sp.)

Larva up to 10 mm long, pupa (14a) somewhat shorter. Hanging with snorkel-like breathing tubes on the surface of the water can move twitchingly. Larva eats plant and animal microorganisms and detritus.

15. Horse sails

(Haemopsis sanguisuga)

Up to 15 cm long, black. Devours smaller aquatic animals such as insect larvae, worms, etc. Has a suction cup at the front and rear end. Swims well. Harmless; related to the medical leech.

16. Mud tubeworm

(Tubifex sp.)

Up to 85 mm long, red; mostly in large colonies. Lives in vertical tubes, cemented with slime, in which the front end of the animal is, while the protruding rear end carries out pendulous breathing movements. Food: organic sludge particles.

17. Mud snail

(Lymnaea stagnalis)

Adult 45-60 mm long, 20-30 mm wide. Creeps on a tape of slime, often also on the underside of the water level. Scrapes off algae from aquatic plants and stones or bites off soft, even decaying plant parts, occasionally also eats spawn and carrion. Like any snail, it comes to the surface of the water to draw air and pushes the breathing hole out of the water. Can escape into the depths at lightning speed by expelling air from the respiratory cavity.

18. Mud snail

(Radix sp.)

15-20 mm long, 12 mm wide. Way of life like European mud snail.

19. Moss bubble snail

(Aplexa hypnorum)

12-15 mm long, 5 mm wide; Lung snail. Animal black-blue with long antennae. Skin smooth, shiny, brownish, translucent.

20. Ramshorn snail

(Planorbis corneus, family plate snails)

Diameter up to 30 mm, height 12 mm. Lung snail, lives mainly on the bottom of the water and primarily eats detritus. Seldom comes to the surface for air. A thin fold of skin protrudes on the left side, which presumably has a gill function.

More small animals

21. Marsh snail

22. Juggler

23. Piston water beetle

24. Fear swimmer beetles

Selected small animals in stagnant waters I

The corresponding short biographies can be found above

  1. Larva of a dragonfly of the Aeshna type
  2. Larva of a flat-bellied dragonfly
  3. Larva of a dragonfly
  4. Mayfly larva
  5. Water strider
  6. Swimming bug
  7. Water scorpion
  8. Stick bug
  9. Back swimmer
  10. Row bug, water cicada

Selected small animals in stagnant waters II

The corresponding short biographies can be found above.

  1. Yellow beetle larva 11a. Yellow fire beetle
  2. Little swimming beetle
  3. Caddisfly larva
  4. Mosquito larva 14a. Mosquito doll
  5. Horse sails
  6. Mud tubeworm
  7. European mud snail
  8. Mud snail
  9. Moss bubble snail
  10. Ramshorn snail

Brief biographies of some aquatic insects

Water strider

In bays rich in plants and sheltered from the wind, the lively hustle and bustle of the water striders attracts our attention. With legs spread wide apart, these peculiar insects, which experts assign to the sex of the bedbugs, slide jerkily over the surface of the water. Their legs are covered with water-repellent hair, which prevents them from sinking into the water. Their slim bodies, pointed at the front and back, are carried by surface tension, just like a greased pin that is placed on the membrane of water. With the enormously long, widely spreading middle legs, they perform powerful rowing movements, which propel them forward up to 60 cm with one stroke. The rear legs, which are sloping backwards, act as a steering wheel. If you try to catch a water strider, it usually successfully eludes our access by jumps up to 10 cm high in quick succession.

The relatively short, forward-facing front legs are primarily used to catch prey. It is primarily small insects that have fallen into the water that fall victim to the water strider. When locating the prey, the sensitive hairs on the lower limbs play an important role by registering the vibrations caused by the insects wriggling in the water. Like all predatory bedbugs, the water striders occasionally attack weaker conspecifics. Before the onset of the cold season, they go to the mainland to hide in suitable hiding places.

The graceful pond runners are also among the bedbugs that live on the surface of the water. In contrast to the water striders, they prefer to stay in the dense bank vegetation. They stalk leisurely on their long, thread-thin legs through the plant jungle and hunt all sorts of delicate insects such as aphids, mosquitoes and mayflies.

Back swimmer

The actual water bugs spend almost their entire life under the water level. Best known are the back swimmers. As the name suggests, the members of this family always swim with their backs down.

The common back swimmer, which is common in all small bodies of water, reaches a length of about 1.5 cm. The light brown wings, which are folded like a roof over the abdomen, form the keel of the swimming animal. The broad head has two large compound eyes and a short, powerful proboscis.

The back swimmers usually stay in the uppermost layers of water, which they row skillfully through with sweeping strokes of their long hind legs. They always carry a supply of breathable air with them, which is mainly held in place by four rows of hairs on the flattened stomach side. Two additional air reserves are located on the chest and under the wing covers. The effect of this air cushion is that the animals are specifically lighter than the water and are passively lifted to the surface by the buoyancy, where they regularly renew their air supply. In doing so, they support themselves with the two front pairs of legs from below on the surface membrane and stretch the tip of the abdomen with the two breathing openings a little out of the water.

As skilfully as the back swimmers move in the water, they crawl awkwardly on land. In return, the well-trained wings enable them to fly quickly and for long periods of time. However, they cannot take off directly from the water, but must first go ashore and let their wings dry. In contrast to the water beetles, they prefer the warm hours of the day for their overland flights. The landing takes place in a dive with the wings applied directly into the water.

All back swimmers are predators. They mainly eat insects that have fallen into the water or chased on the ground, but they also do not spare amphibian larvae and even juvenile fish. The prey animals are grasped with the front legs, pierced with the trunk and sucked out. If we are not careful when catching back swimmers, we will also make very unpleasant acquaintance with their proboscis. It is not for nothing that they are popularly called "water bees". If you still want to risk catching a back swimmer, you should definitely note that the honey bee always stings in the back, whereas the water bee stings in front!

After mating, which takes place in spring, the female sinks the approximately 2 mm long eggs into the stalks of various aquatic plants with the help of her laying tube. The larvae that hatch after a few weeks, apart from the missing wings, are completely similar to their parents and indulge in the same predatory way of life. After moulting five times, they are adults. As with dragonflies, the transformation into a sexually mature, winged animal takes place gradually, without the involvement of a pupal stage.

The full-grown back swimmers overwinter in vegetated waters. Your whole body is then enveloped in a thick layer of air. This acts as a physical gill when the insects are blocked from contact with the water surface by a layer of ice, i.e. it removes dissolved oxygen from the water to the extent that it is consumed by breathing.

Row bugs

The row bugs, which are distributed worldwide with over 200 species, differ significantly from the back swimmers both in their physique and in their way of life. They are small to medium-sized insects with a flattened body on both sides. The smallest native species measure only a few millimeters, while the largest reach a length of almost 2 cm. The row bugs usually stay at the bottom of the water, where they dig through the mud with their shovel-shaped front legs in search of food. The completely harmless animals feed mainly on algae, which they pierce with their short proboscis and suck out.

Like all aquatic insects that rely on atmospheric air, they have to emerge from time to time to get some fresh air. In doing so, their front bodies penetrate the water level for a fraction of a second and then immediately disappear back into the depths.

During the breaks they anchor themselves with the middle pair of legs to water plants or other objects. As soon as they let go of them, they rise to the surface like a cork cone because of the air they breathe with them. They row very skillfully with their flattened hind legs, which are thickly covered with webbed hair. When the swimming movements interact with the buoyancy, they reach such a speed that they can effortlessly shoot through the membrane of the water and take off straight away for flight. The row bugs are generally very fond of flying. In their search for a suitable body of water to live in, they sometimes cover considerable distances.

It has long been known that row bugs are insects that make music. On warm spring evenings they produce chirping sounds under water that can be heard several meters away. This peculiarity has given them the popular name "water cicadas". The chirping comes about when the animals stroke the inside of the fore legs, which is covered with stiff bristles, over the grooved edge of the trunk. Depending on whether the stridulation is done with both legs at the same time or alternately, two different tones are created. As with the grasshoppers, crickets and cicadas, only the males are gifted with voices in the row bugs. The females are dumb but by no means deaf. The males' song of love shows them the way to their sex partners during the breeding season.

The females stick their spherical eggs to the leaves and branches of aquatic plants. In Mexico, the Indians sink willow twigs into the water, on which the oar bugs lay so many eggs that they form a moss-like, white coating on the twigs. This "bug caviar" is stripped off, dried in the sun and eaten as a delicacy.

Scorpion bugs

Water scorpion

Stick bug

The scorpion bug family is represented by the water scorpion and the stick bug. Although the two species are among our largest aquatic insects, they are easily overlooked because of their excellent camouflage.The strongly flattened body of the water scorpion resembles a dead leaf covered with mud, while the up to 4 cm long stick bug imitates a dry twig.

The most prominent feature that distinguishes the members of this family is a long, thin breathing tube at the tip of the abdomen. They use this like a snorkel by stretching the end a little out of the water to replenish their air supply.

The forelegs are transformed into sturdy robbery legs, the end link of which can be folded against a longitudinal groove in the thighs.

The swimming skills of the scorpion bugs are quite modest. Most of the time they crawl slowly through the tangle of water plants or lurk motionlessly for random insects and amphibian larvae, which they capture with a lightning-fast catch of their predatory legs.

The eggs, which are sunk into floating parts of the plant by the females, have 6 to 9 short, thread-like breathing tubes in the water scorpion and 2 long, in the rod bug. Small brown globules are often found on the body and limbs of the scorpion bugs. These are the parasitic youth stages of water mites. These attach themselves to the joint membranes of their hosts and feed on their blood. At an advanced stage of development, they break away from their host and from then on move freely in the water.

Yellow fire beetle