The ranatre, a carnivorous bug in the pond

Concealed in the weed beds, the ranatre patiently awaits its prey. Under the frightened eyes of the children who observe the fascinating life of the aquatic world.

The "twig" bug of fresh water

It carefully moves its long body, 35 mm, on its 6 long legs, in the middle of aquatic plants. Water is its element. Like a twig, it remains motionless, observing its environment with its large round eyes. She captures her preys with her front legs transformed into ravenous claws, piercing them with her biting and sucking rostrum. The ranatre, Ranatra linearis, insect of the family Nepidae, is none other than an aquatic bug, known as heteropteran, a formidable predator of calm waters, common in the entire Palearctic zone.

It breathes oxygen from the air...under water

The ranatre lives, hunts, reproduces, under water. But it has neither gills nor breathing membranes. Then to find its oxygen it is equipped with a tuba. The end of its abdomen is extended by a long tube, made up of 2 half-stems with gutters, just as long as its body. This respiratory siphon links it to the air, allowing it to feed its tracheal system in air. It prefers to hunt close to the surface, in order to get regular supplies with less effort.

A carnivore on the lookout

At length of respiratory siphon of the surface, twig in the grasses, the ranatre settles and does not move any more. She waits. Aquatic insects, larvae, small crustaceans, tadpoles, and even small fish, are on its menu. If they pass within its reach, its legs fold up on the prey, hold it in a vice, hook and spine effectively close it. The continuation is terrible for the catch. And the observer. Seeing a small tadpole being pierced by the rostrum of the ranatre, being predigested, then absorbed by the hunter, is impressive, and not belonging to this small world is rather reassuring...

A clumsy swimmer

If the ranatre lives under water, swimming is not really her domain. It prefers to move at its own pace from plant to plant, hanging on with its long legs, which are not equipped with swimming bristles like its cousins the Notonectes and Naucores. And if it does not swim, or badly, it is able to leave water, to let itself dry, and... to take its flight. She spreads her wings, of a beautiful translucent blue, and leaves in search of new territories. Surprisingly, she reveals a red abdomen of the most beautiful effect, unexpected under her yellowish colors.

Males and females, aquatic meetings

The reproduction of ranatres takes place in spring. The female pierces the plants with her caudal auger and deposits eggs of about 2 mm, either scattered or in a line, depending on the plants chosen or available. 2 small air filaments are visible to the naked eye. At the hatching, the small ones resemble the adults, 5 larval stages will follow one another during 2 months to lead to the ranatre of final size. Which will live approximately 2 years.

If the ranatre is impressive when it captures its preys, to observe it cleaning itself delicately with its front legs, to stiffen like a twig, to deposit a line of eggs on a water lily, to fly away all colored, is a spectacle of which one does not get tired.

The notonect, a bee with its head upside down

A slender silhouette, the Notonecte criss-crosses the waters of the pond, spinning towards the surface, where it stops for a brief moment, legs and abdomen brushing the mirror. As if posed on the air, in an inverted world.

The freshwater "bee" bug

An essential inhabitant of ponds, the glaucous notonect cannot go unnoticed, a small insect of 15 mm, regularly emerging on the surface, to come and breathe. Always in a characteristic posture, the back downwards, its back legs allowing it to swim vigorously. Aquatic bug, it crosses its cousins, the Ranatre and the Nepe. And is just as carnivorous, consuming its prey with its stinging-sucking rostrum. Among half a dozen species of Notonectinae in Europe, Notonecta glauca is certainly the most common. Its life is entirely aquatic, from the egg to the adult.

It lives underwater but breathes oxygen from the air

Like many aquatic insects, the Notonecte has kept an air breathing mode. Only the larvae just out of the egg breathe under water, through the integuments. As soon as they grow, they must go up to the surface of water and constitute a reserve of air. This will be done at the level of the elytra, semi-membranous upper wings, and the silks of the abdomen. The network of tracheas will thus be able to be supplied with fresh air during the periods of immersion.

Effective hunting techniques

Patient, the Notonectes can hunt on the lookout, waiting for an unwary prey. An efficient swimmer, equipped with vibration detectors, it can also launch into fast, precise chases, where it leaves little chance for crustaceans, insects, worms, and even tadpoles or small fish. Its front legs hold its meal, pierced by the stinging-sucking rostrum. A first channel will allow him to inject a salivary juice paralyzing and digestive. By a second channel it will absorb its liquefied menu.

A powerful vision

The effectiveness of the hunting techniques of the Notonecte is reinforced by a highly sophisticated vision. Its two large black eyes defy the laws of optics and allow it to see under water, on water and above water.

At the same time. The adaptation to its living environment, to the interaction of the aquatic world and the aerial world, is optimal. Posed on the surface of the water, back downwards, tips of legs and abdomen maintained by the surface tension, it watches. Any prey coming from the sky, stranded on the water, or swimming quietly, will be spotted. And consumed.

The backstroke swimmer

Its name describes its appearance, "nocto" meaning back, "necte", swimming. The notonecte splits the water with its belly upwards, its elytra carinated downwards. With its long back legs covered with bristles it propels itself with efficiency, its swimming is fast, incisive, with a jerky rhythm. Placed on the surface of the water in an inverted position, it paddles gently, attentive to the slightest vibration, the slightest movement. Efficient to move in aquatic environment, the Notonecte is much more clumsy on the ground, encumbered by its two long back legs. It prefers to fly away, deploying its two pairs of wings, and in a soft roar leave towards new ponds or ponds to colonize.

Males and females, aquatic meetings

Pairs of Notonectes are formed at the end of winter, after fertilization the eggs are laid in the tissues of aquatic plants. Small larvae emerge, similar to adults, but clear, soft, without wings and reproductive organs. They will evolve to their adult form in five successive stages, and will be ready at the end of the summer to hibernate. The very first heat will see them come to the surface, ready for a new reproductive cycle.

The Notonecte is one of the most present insects of the ponds. A calm water, plants, abundant preys, it will not miss the call. Easy to observe, it is however better not to touch it, its rostrum then becoming defensive and provoking sharp pains similar to bee stings.

The aquatic shrew, a mouse in the pond

It comes out at sunset, scurries along the banks wriggling its long snout, dives into the pond to fish for small larvae. Discreet, the Crossope passes unnoticed.

The shrews, a large family

If we know the common shrew, small but great ally of the gardener, its semi-aquatic cousin, the Crossope, remains unknown. Frequent host of rivers, watercress beds, ponds and ditches, Neomys fodiens belongs to the same family, the Soricidae. It shows the same pointed, mobile snout, with long whiskers; its coat is rather grayish to black, with a well marked white belly. Of beautiful size, it measures up to 10 cm, without forgetting the tail, that is 8 cm more! This makes it the largest of the dozen shrews present in France.

An insatiable insectivore

The aquatic shrew comes out at sunset and is active all night long, looking for preys, mainly small invertebrates. On the menu: underwater, aquatic insect larvae, crustaceans, fry; on land, beetles, snails, worms, and even amphibians and small mammals. If its sight is weak, its sense of smell and hearing are excellent. Reinforced by mobile vibrissae, real underwater detectors. Its preys thus located, it seizes them with its small red and pointed teeth, poisons them by the toxic juices of its salivary glands. This is an efficient strategy, allowing this small mammal with high energy expenditure to be fed in abundance.

An accomplished swimmer

Water is its element, the aquatic shrew never goes too far from it. If it trots on the banks, it regularly dives with ease, swims between two waters, circulates on the bottom, goes up and floats like a cork.

It is nicknamed the "frame shrew". Its hind feet are lined with stiff hairs, reinforcing its support. Its tail is also equipped with two rows of the same hairs, and plays a powerful propelling role. Its coat is perfectly water repellent, and to complete the equipment, its auditory holes are obturable. An accomplished swimmer that will dig its burrow on the banks to house its young.

Many young

From April onwards, Crossopes are concerned about their offspring. Males and females meet each other, sometimes a little harshly. Through a small hole of 2 cm in diameter, the female will enter her carefully dug burrow. She will line it with plants rolled into a ball to accommodate 6 young on average. Her gestation will have lasted 2 weeks, 3 at the most. The reproduction will take place until September, the peak of the births being in May-June. The young will become adults after a few months and will reproduce in general the second year.

They will live at best 2 years. Mortality in the aquatic shrew is important, in the young as well as in the adults, especially during the breeding season.

Light traces

Discreet, nocturnal or crepuscular, the Crossope is difficult to see. Minute traces let us guess its passage. The fine and humid mud of the banks will be marked with light prints, with five fingers, without webbing. The posterior foot will measure hardly 1 to 1,5 cm, the anterior one will be even smaller. The droppings are almost invisible: 5 mm long, for 2 mm of diameter. Tiny droppings can be seen... Occasionally some remains of meals are observed, shells of snails, cases of caddisfly larvae, or better a larder supplied with preys half consumed. Other indication of presence, small acute nocturnal cries...

Small discreet mammal, the aquatic shrew plays an essential role in the aquatic ecosystems. But the degradation of its habitats is beginning to impact its populations, on the IUCN lists it is classified as a species of minor concern on the whole French territory, but in some departments the species is becoming almost threatened, vulnerable, even endangered.

The dragonfly, a useful insect in the garden

The dragonfly is an insect easily identifiable because of its large size, its translucent wings and its large faceted eyes. A carnivorous predator, the dragonfly is a useful insect in the garden.

The dragonfly is an animal that enjoys a good reputation among gardeners, and rightly so! This animal is indeed a formidable predator both when it is a larva and as an adult. Insect of the order Odonata, the dragonfly can be either of the suborder Zygoptera or of the suborder Anisoptera. The difference between the two suborders lies mainly in the shape of the eyes and the posture of the wings at rest (folded above the body in the zygoptera, or horizontal in the anisoptera).

Whatever the sub-order, the dragonfly is easily recognized by its large size (up to 110 mm wingspan). In adulthood, it has an elongated body with two pairs of wings generally transparent. It always lives near water (river, pond, basin...) for two essential reasons.

The first is that it lays its eggs in an aquatic environment. The second is that water attracts insects in number and it is thus there that it finds the best hunting ground. She enjoys flies and mosquitoes, which she hunts in full flight using a particularly well-honed technique. Its large faceted eyes allow it to count on a very piercing sight. The dragonfly in full hunting can easily make of the hover before melting on its prey. Fertilization in dragonflies is indirect.

The male will inject his spermatozoa in a special bag located on the abdomen of the female. The spermatozoa are thus stored without being fertilized. Fertilization is orchestrated by the female at the most opportune moment, generally during the month of May. Depending on the species, the female can lay up to 600 eggs. The eggs are deposited in the water where they will hatch releasing a prolarva. This one will know several stages of transformation.

The successive moults can last several months to several years depending on the species. During all its stay in water, the larva is a voracious predator. It eats in priority mud worms. The ultimate transformation is carried out out of water.

Unlike the butterfly, the larva does not go through a chrysalis stage. The passage between the stage of larva and that of the dragonfly corresponds to a final moult (known as imaginal moult).

The green frog, an attraction around the pond

The green frog or edible frog (Rana esculenta) is an amphibian that results from the hybridization between the Lessona frog (Rana lessonae) and the laughing frog (Rana ridibundus).

Of the Ranidae family, the green frog is green-brown and measures a good ten centimeters when adult. It populates our ponds, lakes, ponds and streams rich in vegetation that provides shelter. Its main predators are herons, pikes and snakes.

It comes out of its hibernation in March and resumes its place at the water's edge or on the water lilies. It is in summer, day and night, that we hear them the most. The males emit their songs especially at the end of the day or during the night to attract the females which will lay after the freshness of the gelatinous clusters composed of several thousands of eggs in the middle of the plants. After a few days, the tadpoles will appear and will remain in the water until the following spring when they will metamorphose into green frogs.

The green frog is a real attraction around the pond. Essentially an insectivore, it captures insects by leaping over 30 centimeters. It also feeds on earthworms, snails and slugs, and even other amphibians.

In November, with the return of the cold, the green frog will settle down to hibernate either in the mud or in a small gallery dug in the ground.

How to encourage the installation of frogs?

If your pond is colonized by frogs, the summers will be noisy! But what a show around the water. Children and adults alike will be delighted to watch them snatch up passing insects.

To help them settle in

• Install large rocks around your pond that will provide shelter for the winter but will also encourage the development of insects that will appreciate these shady and humid spots.
• Install a lot of vegetation on the edges of the pond.
• Install many flowers (lavender, perennial geranium, ...) that will bloom in a spread out manner from March to November. The flowers will attract foraging insects like bumblebees, bees and butterflies.
• Also install plenty of water plants to make them feel safe if the frogs need to hide from a predator.
• In winter, if you must handle the rocks, do so carefully, a toad or frog may be underneath.

The frog is protected

The handling of the animal is safe for humans. On the other hand all amphibians and reptiles are strictly protected, as well as their biotopes. The taking of samples in the wild is forbidden.

The great snail, a majestic snail in the pond

Of remarkable size, its elegant shell rolled up into a long point, the great snail crisscrosses the ponds with its quiet glide.

An aquatic snail

The great snail, Limnaea stagnalis, is a snail, with lungs, installed in quiet waters, with slow or non-existent currents. Imposing gastropod, its size can reach 5 to 6 cm, it remains elegant with its lengthened shell with the many spires. Accustomed to ponds, it is found throughout Europe, in the Northern hemisphere, Asia and America, alongside other limneas, all of the family Lymnaeidae.

A siphon to breathe oxygen from the air

If it lives in water, the Great Limnea cannot breathe oxygen. Its lungs need air. The attentive observer will have to wait long moments to see it finally going back to the surface, deploying a siphon, piercing the surface of the water and capturing the air necessary for long immersions. Immersions all the more long as the water will be well oxygenated, the gas exchanges taking place then also by the skin.

Its house on the back

Classic snail, the big Limnée carries its house. A "coat" on its back secretes a calcareous formation, of only one part it manufactures a twisted shell. In which she shelters her soft mollusc body, in case of predation and in times of drought. If its waiting in its shell must be prolonged, it will close the "door" using dried mucus, burying itself if possible in the mud.

A quiet path

On its muscular oval foot, the large Limnea surveys the bottom of the pond, its reliefs, slips from plants to plants. One can see it floating sometimes, between two waters, in ascending or descending movement. At the surface of the pond, between water and air, it is placed upside down and its mucus-covered foot is flush with the air. She glides slowly, feeding on the biofilm formed on the stagnant water.

She grazes, grazes

The great dabbler spends long moments grazing. Its two long triangular tentacles are surmounted by two eyes, below which is placed the mouth. In this mouth is the radula, which could resemble a rasping tongue, covered with asperities that allow it to scrape decomposing plants, to graze the aquatic bottom, to tear some particles from occasional decomposing corpses.

Males and females, aquatic meetings

The great snail, like many snails, is hermaphroditic, the same individual carrying, in a complex anatomy, the male and female sexes. After cross fertilization, sometimes with several individuals, the eggs are laid on the walls or on the plants in extremely adhesive elongated socks. After three weeks, more or less according to the temperature, the eggs hatch and come out tiny Limnea whose body and shell will grow in a few months.

Majestic, slow-moving, the great snail is one of the easiest to observe in the pond. Not very demanding, an abundant vegetation, a calm water and detritus will be enough to welcome it.