The caddisfly, the wood holder of the pond

They populate the bottom of the ponds, hide under the stones of the streams, slip into the rushes of the ponds... The carrion beetle, the wood dragger, the alder beetle, the carpenter beetle, the caddisfly form a family of common insects, with a half aquatic, half aerial life cycle.

A mason insect

It reveals its presence when it moves, some debris of the pond seeming to set in motion. The larva of Phrygane lives in small tubes from 2 to 4 cm long, made of various materials. Of the group of Integripalpia these mobile Trichoptera of greenish tint let exceed of their sheath a short and broad head with the eyes little marked, with the short antennas, with the crushing mouth. The six pairs of legs are visible, the first pair rather short, the others long and thin. The elongated abdomen ends with a pair of hooks hidden in the sheath.

Cousins of the butterflies, the Phryganes do not weave a nymphal cocoon but a permanent shelter.

A house of silk and eclectic materials

The small larvae of caddisflies build their first shelter very early. The front legs seize and sort the available organic and mineral materials, the mouth apparatus cuts them, adjusts them. Two specific glands near the mouth produce a liquid and sticky silk, cementing the whole, lining the inside of the tube for an optimal comfort.

The finished sleeve forms a funnel and remains open at both ends. Blending into the environment, it offers perfect camouflage and effective protection. It will be different according to the materials available, and especially according to the species of caddisflies, each one having its preferences.

To each species its sheath

If certain species of caddisflies make a sheath of leaves cut in large pieces assembled in an elegant tiling, others opt for fine strips, assembled all bristled; others will choose twigs cut and piled up in regular spiral; others still will agglomerate shells of planorbe.

To better resist the current, the caddisflies will weight themselves with tiny pebbles. Each species will thus choose its style of sheath. If their favorite materials are missing, they will adapt, even choosing small pieces of plastic, beads, colored fabrics, identification by the sheath alone becoming uncertain.

A long year under water

Sheltered in their sheath, the larvae will live for most species a good year in unpolluted, well oxygenated water. The external gills, branched or digested, characteristic of each species, are arranged all along their abdomen and allow them to breathe the dissolved oxygen of water. This breathing is completed by a permeability of the tegument, and optimized by the creation of a current circulating between the two ends of the sheath. Conferring to this frame, in addition to the protective and camouflage role, a physiological function of first importance.

Diversified menus, a fast growth and an adjustable sheath

The larvae of caddisflies move on their four long locomotor legs. Detritus feeders in general, they scrape the substrates, crush the organic matter in decomposition. Helped by their front legs, they capture tiny particles in suspension, algae, invertebrates...

It will take them less than 4 months, up to 7 successive moults, to reach their maximum size. And with each moult, they will have to enlarge their sheath. Widening it on the head side while cutting the opposite small end.

A swimming nymph

Its maximum size reached, the larva is ready to metamorphose. It closes the two ends of its sheath with a membrane of woven silk, and pads its interior. The wing sheaths of the nymph develop, the long antennas of the future adult are folded in ventral position. Also appear dorsal spines, a pair of mandibles, swimming silks on the second pair of legs: the spines will enable him to release itself from its nymphal sheath, the mandibles to cut the trapdoor of exit, the silks to swim towards the surface. Where it will cling, one night, to an emerged substrate, then will metamorphose into adult, and will take its flight.

An adult with silk wings

Brownish to beige, the adult caddisflies are easily recognized. Elongated, of average size, 2 to 4 cm, they carry long and fine antennas projected towards the front, large well developed eyes. They could look like moths. But unlike their distant cousins they fold their four wings in the form of a roof and carry many bristles, sometimes long bangs. Trichoptera meaning silk wings. Also they do not have a spiral proboscis. Neither do they have mandibles. Just like Ephemera, the adult caddisflies do not eat, devoting themselves exclusively to their reproductive task.

An ephemeral life

The spring or summer appearance of caddisflies is short-lived, the time of a pause in a cave to complete their sexual maturity for some species, a few days for others. Briefly, males and females meet. The eggs will be laid in clusters on submerged plants, or just on the surface, as soon as they hatch the larvae enter the aquatic environment. The adults are stranded on the surface of the water, for the greatest delight of trout and other predators.

Common, diversified, caddisflies play an important role in aquatic habitats. Food source for many animals, fish, invertebrates, but also birds, they are also appreciated by fishermen, for the larvae as bait, the adults serving as a model for fly fishing.

The mosquito, a blood drinker in the pond

Frogs, garter snakes, turtles, none of the inhabitants of the pond escape the bites of adult mosquitoes. But they feast on their aquatic larvae, and few of them escape.

The world's ponds busy

Wetlands around the world are home to mosquitoes. Their eggs, and then their larvae, live in the water. The winged adults, while often foraging, are in search of blood, in all vertebrates. The inhabitants of the banks of the pond know them only too well.

In Europe, they are mainly solicited by Aedes, rather in temporary wetlands, Culex and some Anopheles in stagnant waters. In their family Culicidae we will also find the Coquillettidia, with a very original respiratory mode.

Aquatic larvae, air breathing

Mosquito larvae live in water but continue to breathe like terrestrial insects. They look for air on the surface of ponds, positioning themselves head down, vertically, for the Culex. A well known posture where we see the small silhouettes grouped, long and thin, as if hooked to the surface by their respiratory siphon. They stay there, breathing in and out. The Anopheles, without siphon, will lie under the surface allowing the air to circulate in their tracheas. And the Coquillettidia will never come to the surface. But then? From their pointed respiratory siphon they pierce the tissues of aquatic plants, and take the necessary air from them.

They feed on waste, nectar and a little blood

From the larva to the adult, from the male to the female, the feeding of mosquitoes differs completely. The adult female is well known for biting, injecting an anti-coagulant, and sucking blood from her prey. All this to bring to maturity her young, eggs that she will deposit delicately on the surface of the water.

Out of this period, the adults fly from flowers to flowers, feeding on their nectar and pollinating them. The larvae will spend their few weeks of aquatic life filtering and cleaning the water. They shake their mouth bristles, creating a water current, feeding on floating microparticles.

Larvae wriggle, adults fly

A mosquito larva has no legs, the observer approaching a tank of water will see them wriggling to disappear towards the bottom, helped by bristles arranged all along the body. The nymph, a strange silhouette with a large thorax floating in the middle of the larvae, is equipped with a swimming paddle at the end of its abdomen. The adult, better known, has a single pair of wings and two pendulums, like all members of its group Diptera.

Males and females, aquatic meetings

The females, with the hematophagous diet essential to the development of the eggs, lay eggs on the surface of the water. They float in small irregular groups in Anopheles, in rafts in Culex and Aedes. A first larva hatches, it will moult three times before turning into a nymph. With cycles of a few days to a few weeks, depending on the species and climatic conditions. Mobile, with a large dark thorax from which emerges a small breathing tube, the nymph will give birth to the winged adult at the surface.

Mosquitoes are not very popular, and often the idea of the pond, of the body of water, is associated with them, with the fear of seeing them invade our gardens. However, in the pond many predators devour them, and dragonflies spare few adults... They are thus essential to this ecosystem!

The grey heron, a fishing wader

The grey heron (Ardea cinerea) is a very shy fishing wader. It can be observed from a distance in the marshes and along the rivers of Europe. Protected since 1975, this majestic heron is the most common heron in Europe.

Nearly one meter high and weighing 2 kilos as an adult, the grey heron is the largest heron in Europe. This wading bird can be recognized by its size but also by its ashy gray plumage (hence its name), its white neck and its black spotted breast. Its white head is underlined by black lines starting from the back of the neck and stretching to the eye. The juveniles have the same physical characteristics as the adults but are more dull.

The grey heron has a long yellow beak which is a formidable weapon for its prey. A great hunter and fisherman, the grey heron feeds mainly on the product of its fishing in the river but also on frogs, reptiles and aquatic insects and small mammals such as mice, voles, field mice or moles. This wader, which is very common in Europe, is a partial migrant. Only in very cold weather does it move temporarily.

In some mild regions where food is abundant, the grey heron is a sedentary bird. Its heavy flight is graceful but slow (40 km / hour maximum). It can be found in some European countries such as the Netherlands, Scandinavia, England, Germany, but also further south in Portugal, Northern Italy and Greece. In France, it nests mainly in the North-East and in the vast marshy areas of the West (Poitou-Charente and Vendée).

The grey heron is a shy animal which does not let itself be easily observed up close. At the arrival of an intruder, it flies away to join a quieter corner. If this bird is generally a great loner, at the time of the mating, it joins its congeners within large colonies, the heronries, perched at the top of the trees. The nesting begins early in the season from February until July. It is the male who chooses the place where the eggs will be laid. The clutch consists of 4 to 5 light blue eggs. The two parents take turns during the 25 days of incubation. The first flight of the juveniles intervenes approximately 50 days after the hatching. The emancipation of the young is fast since in 3 weeks after the fledging, they must be able to manage alone.

The gyrin, a turnstile in the pond

Lively, light, the gyrins crisscross the surface of fresh water with their metallic shine, in a dizzying ballet of speed.

The speedboat of fresh water

They move at full speed on open waters, gather peacefully in the plants and dive to escape from predators. They live between air and water. Gyrins, small beetles of aquatic environments, hold the speed record of floating insects, with their 4 back legs they propel their 12 grams, in random but precise curves, avoiding for sure any collision. These insects of a few millimeters, 6 at most, with varied dark colors, have 3 genera and many species, all of the family Gyrinidae.

A life between air and water

Floating on water, Gyrinids breathe oxygen from the air, like any terrestrial insect. Their tracheas carry gases to all their organs. But at the slightest alert, they dive under water, take refuge in the grass beds, do not move any more. Do they hold their breath, do they have a snorkel like the nephrops or the eristalus? No, just before diving, with the tip of their abdomen, they capture a bubble of air, a precious reserve that ensures them to go back up when the danger has passed. Their daily activities, such as hunting, take place on the surface.

A predator on the water mirror

Untiring, the Gyrins watch and survey their territory, a vast and totally flat area. With their antennae on the surface of the water, they pick up the vibrations of insects, spiders, shipwrecked airborne creatures, desperately struggling to escape drowning. Spotted, they are seized by the front legs, ingested by a crushing mouth apparatus. And if no aerial prey presents itself, mosquito larvae, small crustaceans, will at some point pass near the surface, within reach of the paws of a hungry Gyrin.

Eyes for water, eyes for air

Between air and water, how can the Gyrin switch so quickly from an aerial hunt to an aquatic hunt? How does it spot a predator from the depths or diving from the sky? Its adaptation is simple, obvious: its eyes are divided into two parts, one for aerial vision, the other for underwater vision. To surprise him becomes a real challenge. And to escape him too. Especially since its adaptation to swimming is also remarkable.

Swimmers and trainers

The spectacle of the Gyrins spinning, twirling, so fast that the eyes cannot follow them, announces long afternoons of contemplation at the edge of the pond. Their back legs are said to be swimming, equipped with bristles they offer a powerful support on the water, activate vigorously several tens of times per second, and propel the Gyrin at high speed. The oars at rest are folded in a special box, so the small carinated and oiled body of the beetle finishes its slide with fluidity...

Males and females, aquatic meetings

Following a terrestrial hibernation, under the stones of the banks, the couples of Gyrins are formed, the females will lay about thirty eggs on the plants. These eggs will give birth to a larva which, as with all beetles, does not look like the adult. 15 mm long, whitish, thin, it crawls on the bottom or wriggles in the water, feeding on small animals. Its breathing is aquatic, abdominal feathery tracheal gills ensure the gas exchanges of its organism. After three larval stages a terrestrial nymph is formed, the metamorphosis will give birth to the Gyrins whirling on the water.

They float, spin on the water at full speed, they dive and swim, their young breathe under water... And moreover they can fly. Their wings spread, they leave to discover new environments, with calm waters, vegetated banks, with large areas to glide without hindrance.

The dytic, a ruthless hunter in the pond

An imposing shadow rises from the depths of the pond, with a supple and quick swim. A surprisingly large, dark-shelled Carabean pierces the surface of the water for a moment, then disappears. The Dytic is back on the hunt.

picture credit: dytic.over-blog

An aquatic beetle

Large family of beetles, the Dytiscidae have many genera in Europe, all well adapted to the aquatic environment. Eggs, larvae, adults, in their cycle everything happens under water. Only the nymphs make a brief excursion on the banks. Among more than a hundred species, the bordered dytic, Dytiscus marginalis, is one of the most common and most remarkable, by the size of the adult, 3 to 4 cm, its dark carapace, with elytra with metallic reflections, bordered of golden yellow. Its larva is no less astonishing, even larger than the adult, up to 6 cm, with a characteristic look, like an inverted question mark. Adults as well as larvae are merciless predators.

An aquatic life, an aerial breathing

If Dytics spend their life underwater, they have kept their aerial breathing, from the time of their distant terrestrial ancestors. Regularly, the adults go back to the surface, let emerge the end of their abdomen, capture air which they store between elytra and abdomen. Their reserve thus made, they spin in the vegetation. The larva has not adapted to aquatic breathing any more than the adult, no gills, no exchange membrane. It undulates towards the surface, head downwards, body arched, the end of its abdomen pierces the surface of the water, a drop of air is sucked in, feeding its network of tracheas.

The water tiger

The bordered Dytique has a reputation of voracious hunter. Deserved. Tadpoles, larvae, mud worms, fish, newts, no inhabitant of the pond is spared. And if the dytics regulate the inhabitants of the pond by cleaning up the populations, consuming the weakened and sick individuals, their pullulation can lead to the disappearance of all life in the pond. The adult, lying in wait in the vegetation, springs up with speed, following a lightning chase, the prey is captured, consumed with a crushing mouth apparatus.

Its larva is even more formidable. Thin, long, it carries a flattened head, provided with arched mandibles, spread out during the stalking. The prey passes, the mandibles close again. They have an action of claws, but also of syringes, instilling by two small channels of digestive juices which will liquefy the menu. Will not remain any more but to aspire it, by the mandibles also.

Just before becoming nymph, a larva can consume up to 30 preys per day.

Swimmer, diver, air sailor

The bordered dytic is a skilled swimmer, diver. Lively, fast, it has a body cut for swimming. Oval, flattened, carinated, bevelled, it splits the waters with ease. Its back legs equipped with natatory bristles row vigorously in a beautiful set. They handicap him however for the walk, of possible exits of water see him bumping painfully on the banks. On the other hand, if it walks badly, the Dytique can fly. The dark nights a light humming rises from the pond, the Dytics spread their elytra, spread their transparent wings, and fly away towards other spaces to live.

Males and females, aquatic meetings

The couples of Dytiques meet in spring, the males impregnate the females by maintaining themselves on their backs using the suction cups of their front legs. The eggs are aquatic, the larvae are born after 2 to 3 weeks, they will go through three stages before reaching the bank to become nymphs. Buried in the sand, in less than two weeks they will metamorphose into an adult still a little pale and soft, which will immediately return to the aquatic environment with its clumsy walk, where it can live for several years.

The bordered dytic is one of the most remarkable inhabitants of the pond, inviting itself according to its nocturnal flights, leaving without warning when the preys become scarce. A dense and varied vegetation, a diversified fauna, allow to perpetuate its presence, without excess however.

The common toad, a useful batrachian for your garden

Spring is approaching, slowly but surely, and for some, it will be tomorrow, the day after tomorrow; only the temperature, humidity and light will trigger the awakening after 3 to 4 months of winter rest of the most repulsive "monster", the most popular belief and always associated with witchcraft.

But, did you know that this host of the earth, of forests, gardens, swamps, ditches, ponds, of the plain as well as the mountains, of the city (it can be found in some parks in Geneva) as well as of the countryside, is the most useful for the protection of your salads?

Come on, the author is delirious; well, no, because this "residue of a disgusting elixir extract that everyone worships..." plays a crucial role in the destruction and regulation of all kinds of invertebrates such as earthworms, slugs, caterpillars, beetles, ants, and many more, whose existence you could not imagine.

It is the largest toad: the female can reach 12 cm (even 18 cm in the south of Europe), the male reaches quietly 8 to 9 cm and is provided with strong forearms whose three internal fingers are provided with rough and blackish pads named "callosities", in period of reproduction only. One can also recognize this one by seizing it, it will then emit some croaking while the female will remain mute.

35 years of existence, not without risk!

The life span of our "salad protector" can exceed 35 years unless, by mistake, it ventures to swallow a poisoned slug, hence the importance of using natural methods (saucers filled with beer) to eliminate gastropods if the damage done to the vegetable garden is major.

The natural predators of the common toad are mainly the garter snake, the hedgehog and certain birds such as the crow. Another factor that shortens the life of this amphibian is the high mortality during spring migration on our country roads crossing their territories. Indeed, as soon as the weather conditions become favorable for awakening and reproduction, thousands of toads move to their egg-laying site, which corresponds to their birthplace in general: they must then often cross busy roads. Hundreds of them will perish under the wheels of unconcerned motorists or even those who cannot do otherwise because there are so many of them. Remember, the road is not only slippery when it rains, it is doubly dangerous when it rains and when the amphibians are present.

Fortunately, there are now amphibian migration "tunnels" that are placed under the roadways that cross important migration routes, but there are still too few...

The reproduction of toads

After these asphalt considerations, let's get back to our toad. The males are so eager to find a mate that they can cling to a female for up to ten times, and she may drown under the burden. Females can sometimes be seen dead from disembowelment due to the power of the forearms of the first male clamped who was clutching harder and harder while other suitors were clutching in turn.

About reproduction, let us point out that the female is able to lay about 8000 eggs arranged in double gelatinous cords hung on aquatic plants. The tadpoles, which live in a gregarious way, are easily recognized by their modest size (3cm) and their black color; they gather in bands near the surface and at the edge of water points where the temperature is higher. Most of them will perish from predator attacks (aquatic insect larvae, newts, fish), or from unfavorable conditions (pollution, drying up) and only 1% of them will produce an adult capable of giving offspring. The obstacle course is particularly selective for all toads and frogs.

The "toad rains" as they were called in the past are due to the massive emergence of young after heavy rains. These, as soon as the metamorphosis takes place, which generally takes place at the end of June, take refuge in small crevices of the ground or under stones and plant debris. They will then lead all their life a terrestrial existence (except for the laying of eggs), crepuscular and nocturnal. The toad is a homebody, seems to know its hunting territory very well and always returns to the same refuge, year after year.

Reminder

The handling of the animal is not dangerous for humans. On the other hand, all amphibians and reptiles are strictly protected, as well as their biotopes. The taking of specimens in the wild is forbidden.