The insects of the pond, necessary for its balance

The success of a pond in the garden is based on the establishment of a complex ecosystem where insects play an important role since they are, in spite of themselves, a real "pantry" for the fish and amphibians of the pond!

At the slightest water hole, life swarms! If the fish and plants can obviously be put in place by the hand of man, the arrival of the insects is entirely (or almost entirely) the work of nature! And we must admit that nature is well done, since it only takes a few weeks at the most after the installation of a pond to see many species of water flea insects flocking in.

The main purpose of these insects is to provide a food source for the fish and amphibians in the pond. This is true if the pond has been well designed of course! Indeed, to ensure the survival of these insects, you must think of providing them with a small shallow corner that will keep them safe from adult fish. This small attention will also be welcome to provide a shelter for fry and small fragile fish.

Generally, the first to colonize the wetland are mosquitoes. These insects, which are very unpleasant for the fragile skin of humans, are a real godsend for fish, since their larvae, which lie flush with the water, are a king's meal for any well-constituted fish.

Apart from mosquitoes, many other species will gradually colonize the space, including the very graceful dragonflies, but also detritivores, phytophagous, insectivorous predators, not to mention certain exclusively aquatic species such as dytics and water bugs.

All these insects will attract amphibians and birds to the pond. Although all these insects promote biodiversity without compromising the pond's internal balance, some species should be closely monitored, such as the caterpillars of the water lily (a small butterfly) and the water beetle (a small beetle) whose larvae shamelessly devour the leaves of aquatic plants.

The same goes for aphids, which are best drowned from time to time by immersing the infested leaves in water to avoid carnage on the water lilies! With one simple action, the greedy aphids will become a real feast for the fish!

The great variety of insects attracted by stagnant water is a guarantee of balance for the pond. To preserve it, it is obviously imperative to ban the use of pesticides in the garden!

Aquatic insects

Apart from dragonflies, few insects catch our attention when we observe a body of water. This is a big mistake, because this little six-legged world is very fascinating...

Specificities of aquatic insects

Many insects live in contact with water. Essential to the ecosystem of ponds, pools and rivers, they help maintain a natural balance in these particular environments. Some of them, such as mosquito larvae, feed on bacteria or small particles suspended in the water, others, such as dragonflies or dytids (Dysticidae), carnivorous, eat living prey, and still others, such as Hydrophiles or Coleoptera, voraciously devour aquatic plants.

These insects have the specificity of seeking out wetlands, they are fond of banks, some live under stones, others find shelter in dead branches, others will spend their entire lives in water. Thirteen orders of insects share the aquatic environment but only five have species that live exclusively in water, such as the dytics and water bugs.

In their larval state, many insects develop underwater; this is the case of the dragonfly which will take two years to emerge from the water to take flight or the mosquito and the gyridinae beetles.

A well-oiled food chain

As we have seen, aquatic insects feed in a variety of ways and thus participate in the ecosystem of the water bodies where they live. But they are also part of a very organized food chain, and serve as food to many predators. Flying insects are of particular interest to birds, but also to amphibians. The larvae and insects living constantly in the water will be consumed by carnivorous fish, ducks or herons.

Some common aquatic animals

• The gerris, better known as the water spider. Very common, it glides gracefully on the surface of calm waters with small hairs waterproofed by a thin oily film present at each end of its legs.
• The nepus, otherwise called bug or water scorpion is an insect that moves at the bottom of stagnant water, it is very common in these environments.
• The dragonfly and its variants. Well known, it spends its youth under water in the larval state to transform into a formidable flying predator during its adult life.
• The mosquito is also born and transformed in water, going through four stages of growth (egg, larva, nymph and adult) in a record time varying from 10 to 15 days depending on climatic conditions and species.
• The notonect or water bee is a water bug that swims backwards and whose bite can be painful if handled without precaution. 
• The linear ranate resembles a phasma, it is a species of bug that uses its front legs to capture its prey that it will empty with its powerful rostrum.
• The fringe dytique is a common beetle that can exceed 3cm. It can attack larvae of amphibians or fish.
• The mayfly is well known by its short life and its larva which is aquatic.
• The chironoma is a small insect resembling mosquitoes but which does not bite. The adults gather at the end of the day to form characteristic swirling clouds at the time of reproduction. Its larva, the bloodworm, is well known especially to aquarists.

Mayflies, the nourishing manna of the pond

Thousands of mayflies take flight over the pond in the heat of May. For a few days, a few hours. Without eating, they are present for a moment, to ensure the perenniality of the species.

The mayfly 

2 to 3 cm long, it can be recognized by its arched body, its slender abdomen prolonged by thin rings, its vertical wings, its reduced antennae. The mayfly belongs to the large group of Ephemeroptera, along with hundreds of cousins difficult to differentiate from each other as they are so similar.

All over the world they are found in thousands of species, under all latitudes, except the coldest. Except also Iceland and some Pacific islands. Their life is divided between the aquatic world, for their larvae, and the air, for the adults.

An ephemeral life

The adult mayflies fly away in spring, for a few hours, 2 to 3 days at the most. Their so short life is devoted only to the reproduction, as soon as emerged the males fertilize the females, the long front legs allowing a firm catch. Immediately, the mayflies will lay eggs.

For certain species, the eggs will be released in full flight, others will pose them on water or just on the surface, others still will fix them to immersed substrates.

A single female will emit 500 to 6000 eggs. Then will disappear, without having even sought to nourish itself. Its digestive organs and mouth parts, regressed, do not play any more any role.

Long life to the young

The eggs of Ephemera will give birth to small larvae with the entirely aquatic life. They breathe with external gills, 2 rows of 7 arranged along the abdomen. Their shape, aspect, differ according to the species, and allow determinations with a magnifying glass. Just like the antennas, more or less short. The larvae are remarkable for their long and fine cerci, 2 to 3, extending their abdomen. To feed they have crushing parts, and are for the majority detritivores.

But some species have adapted to other food regimes, scraping the substrate, filtering, sometimes predatory. They need about twenty moults, during several months, to reach a pre-adult stage, the subimago, rapidly transforming into a formed adult.

From mountain streams to marshes

Mayflies are found throughout the world in a wide variety of species and habitats. From mountain streams to calm rivers, from ponds to marshes, all wetlands welcome them. The larvae can be burrowing, crawling, swimming... They disperse according to the currents, carried in the plumage of the birds. Adapted to many environments, extremely prolific, they play an essential role in aquatic ecosystems. Bats, birds, amphibians, fish and insects all take advantage of this abundant food source. Called "manna", for the enormous biomass thus provided.

Nowadays, we hardly see the spectacular spring swarms of mayflies anymore. Victims of pesticides, of the loss of their habitats, of their attraction for artificial lights, they are in clear regression. What if the manna of the wetlands disappeared?

The damselflies, an aerial ballet above the pond

From spring to autumn, the damselflies come to brighten up the pond, twirling between the rushes, typhas and sedges. Experienced pilots, they chase their prey in full flight, putting in place astonishing amorous parades. Then they disappear at the beginning of the winter, leaving their aquatic larvae to survive the bad season.

An international reputation

The Damselflies stand out among the insects of wetlands by their colorful hues, metallic blue, fire red, straw yellow, bright turquoise ... Their four finely ribbed translucent wings are often shaded with the colors of the body.

At rest, they fold like a book along their fine and graceful body. Characteristic differentiating them from their cousins the dragonflies, keeping them well spread out, in horizontal position.

Damselflies, also called Agrionians, Zygopterans, are classified among the Odonates, hundreds of species exist around the world, all leading a half aquatic, half aerial life, the young growing underwater, as larvae.

A half aquatic, half aerial life

At their birth, the small larvae of Odonata have an entirely aquatic life. They must therefore breathe under water. In damselflies, three gill lamellae of variable shape can be observed at the end of their abdomen, depending on the species. Folds near the rectum also play a role in gas exchanges.

After several successive moults the larvae will leave the aquatic environment and will have to adapt to an air breathing. A network of fine tracheae runs through the body of the damselflies, bringing the air as close as possible to the cells.

Fearsome predators

Damselflies, both larvae and adults, have effective and deadly hunting techniques. The larvae, brown to gray, go unnoticed on the muddy bottom. Especially since they do not move. They wait. Eyes, antennas, sensitive bristles, on the alert. If a prey passes at a distance that seems to maintain a certain but illusory security, it deploys a lip mask. At great speed. And catches small insect larvae, crustaceans, worms... The victim is crushed, swallowed. The mask then folds under the head, "masking" in certain species a part of their face. To leave towards a new hunting territory, the larva moves on its six legs and undulates with its gill lamellae, which act as fins.

Hunting pilots

Adult damselflies have nothing to envy to their young. They hunt in flight. Mosquitoes, butterflies, mayflies, flies, all small insects are potential targets. Their big round eyes, well detached, spot any movement. Fast, with their four wings, they melt on their preys, capture them with their front legs, bring them to their mouth, crush them before swallowing them. During the summer season, they fly all over the world, regulating many human pests.

Males and females, aerial meetings

In spring, real ballets begin above ponds, puddles and streams. The male Agrions locate their territory, watch it, invite a pretty partner. They delicately seize her by the neck, from the end of their abdomen. The female thus maintained will bend to bring the end of her own abdomen towards the penis of the male. This one being located at the beginning of the abdomen, it follows a figure of speech evoking a heart. And the eggs are ready to be fertilized.

A laying under close supervision

The fertilized damselfly decides to lay eggs. Under the close supervision of her partner. Depending on the species, he will hold her by the neck during the whole operation. Or he will stay close to her to ensure a close protection. The laying, dozens of eggs, will be made inside the plant tissues, under the leaves of water lilies, along the stems of rushes, cattails...

The first larva will leave its plant hole, and will quickly take the long and fine aspect of the larvae of Zygoptera. Several moults will follow one another during several months, even several years according to the species, to reach the size of transformation into winged adult. The larva then climbs on the plants, tears its old envelope, deploys and dries its wings and its new body before taking its flight.

The newt, between land and water

One of the most discreet animals, the newt, leads its peaceful life between stagnant water and forest cover, to the rhythm of the seasons. More and more rare, some of its species are classified in the Bern Convention; it is thus necessary to protect this small amphibian to preserve it.

Who are you?

There are several species of newts all belonging to the genus Triturus: the palmate newt (Lissotriton helveticus), the spotted newt (Lissotriton vulgaris), the crested newt (Lissotriton cristallus), the marbled newt (Lissotriton marmoratus) and the alpine newt (Lissotriton alpestris).

Each of these species lives in a particular habitat between water and land throughout their life cycle.

The newts are urodelic amphibians, that is to say that they have a tail, which in their case is flattened on each side. They have a larval life which takes place entirely in water, then an adult life shared between dry land, ponds, water holes and small calm rivers. Their rhythm is very linked to the climatic conditions; In winter, they begin a period of rest, generally on the ground under a stone or plants if the winter is not very rigorous. In altitude, the winter can be spent under water.

Newts are carnivorous and feed on small mollusks, worms, mosquito larvae, frog eggs and insects.

Breeding always takes place in aquatic environments around April. After a nuptial parade, the male deposits a spermathopore at the bottom of the water which will be absorbed by the cloaca of the female. The latter will then lay one or two eggs which she will hang on the surrounding aquatic plants. The larva, similar to a tadpole, will develop in the water during 3 months until the end of the summer, period when the metamorphosis will be complete and when the young newt will leave the water to begin its adult life. It will generally spend the winter on land, then will dive back into the water for its mating. This is followed by an amphibious life until the next winter.

The different species of newt

The marbled newt is present in the forest environments of the South-West and the West of the country. It is recognizable by its green body punctuated with black spots and its lighter belly. It can reach 15 cm in length. This newt appreciates the sun and living waters. It can reproduce with the crested newt which appreciates the same living conditions. This last one has a grey and brown spotted skin, warty like a toad and presents two crests, a caudal and a very crenellated dorsal. Its belly and the inside of its legs are orange. It is found in a line from Lyon to La Rochelle. These two species are listed in Appendix II of the Bern Convention.

The palmate newt has webbed hind legs and can be recognized by its rounded snout and its greenish body spotted with black. Small in size, it does not exceed 9 cm despite its tail extended by a short filament. It is present on all the territory except Corsica and the extreme South-East.

The alpine newt lives in stagnant waters sheltered from the sun, north of a line that extends from Avignon to Saint-Malo. This bluish-gray newt with an orange-brown belly can live at altitude, up to 2500 m. The male does not exceed 8 cm while the female can reach 12 cm in length. During the reproduction period, the male is decorated with bright colors.

The shubunkin, a small and colorful fish

The Shubukin (Carassius auratus) is a fish of the Cyprinidae family that has a similar shape to the common goldfish, but is smaller and more colorful. Native to China, the Shubunkin likes to live in fresh water with little movement and in streams with little current.

Description

Shubukin are calico, mostly bluish with extensive red spots and smaller black spots scattered throughout their body. Adults they measure about 25 cm. There are three varieties of Shubukin: the Bristol Shubukin, the American Shubukin which is more streamlined and has less fin length than the previous one, and the London Shubukin which is a little smaller, with a shorter, less wide and less lobed tail fin than its Bristol cousin, which can reach more than half of the total size of the fish. The pectoral and pelvic fins are even numbers, while the dorsal, anal and caudal fins are odd numbers. Females are generally much larger.

Habitat and feeding

In its native country, the Shubunkin lives in fresh and calm water. It is resistant to cold but not to strong frosts. You can install it in your pond in privileged areas where it will feed on small elements found in the ground which it loves to dig. It is omnivorous and is interested in mosquito larvae as well as algae. In cold regions, it will be necessary to bring it into an aquarium during the winter, making sure to provide a minimum of 20 liters of water per individual. Feed it with pellets and chopped cooked vegetables.

Life cycle

In spring when the temperature rises, the spawning period begins for fish that have reached sexual maturity, which is about two years old. The male then adorns himself with small white buttons on the opercules as well as on the first ray of the pectoral fins.

After some parades between the male and the female, the female deposits the eggs on the available supports then a few moments after the male fertilizes the eggs by letting escape its milt. The eggs adhere then to the plants and the surrounding surfaces. Incubation can begin, after three to six days depending on the water temperature a larva will emerge and sink while the swim bladder is formed (2 to 4 days). The small fish will then find the strength to capture an air bubble which will allow it to swim to feed itself and then if the conditions allow it to live a long life (20 years).

The awakening of the amphibians

Every year, between February and April, some amphibians move from their wintering site to their breeding site in wetlands. A journey that involves many dangers that many of them will not resist.

Cycle of amphibians

Amphibians, unlike mammals, do not have the possibility to regulate their internal temperature themselves, which always depends on the surrounding environment. Their energetic needs being less, they allow periods of fasting and therefore hibernation as soon as the temperatures become too cold to live actively. In autumn, amphibians migrate towards their wintering site, most of the time towards terrestrial sites in wooded areas. They then bury themselves under leaves or settle in crevices of tree trunks or rocks. In the spring, they slowly wake up and take the path in the other direction towards a wetland suitable for reproduction.

A perilous migration

Toads, salamanders or newts leave their wintering grounds at the first warm nights of spring to reach the pond or lake where they can reproduce.

Unfortunately, for many of them, this will be their last trip. In the past, they were only subject to their natural predators (birds, snakes, small mammals...), but now they are victims of the worst of them: Man.

Their journey is nowadays more and more full of pitfalls of all kinds: roads to cross, garden fences... Coming out of their sleep, their movement is also slower. Few humans have scruples to run over these little creatures when they are driving their vehicles! However, some of these amphibians are protected and endangered. If you pass them on the road, avoid them and help them to reach the other side of the road to allow them to procreate.

Devices are sometimes set up along the roadside in some regions to capture them in order to move them to the other side of the road to give them a chance to reproduce. Associations are also set up, creating events bringing together their members who come to cross the amphibians during the migrations, whether they are spring or autumn. Finally, there are 'crapoducs' on certain roads. These specific arrangements in the form of tunnels permanently installed under the road allow amphibians to cross without being crushed.

Let's not forget that amphibians, like toads, are also friends of the gardener and help limit the proliferation of certain biting insects like mosquitoes. If you come across them on the road, avoid them and help them get to the other side of the road so they can procreate. 

The goldfish, a classic of the pond

The goldfish is a classic in outdoor ponds. A member of the carp family, this fish is easy to live with in temperate regions since it can withstand progressive temperature changes of a significant amplitude.

The goldfish originates from China where it has been regularly and selectively bred for over a thousand years. Originally, the goldfish was a rather dull Asian carp which gained in color through crossbreeding and hybridization.

From the Cyprinidae family, it is a close relative of the carp while presenting much more restricted measurements what destines it particularly to small outdoor ponds and indoor aquariums.

Like the carp, the goldfish comes in a multitude of varieties. The most common goldfish have a stocky and compact body that is entirely orange-red. This variety usually reaches a maximum of 25 cm in aquariums but can reach up to 40 cm in outdoor ponds.

All these fish have the characteristic to reproduce perfectly and easily in outdoor ponds, less easily in aquariums because of the promiscuity and the voracity of the adults.

Very resistant to temperature changes, goldfish can easily withstand a winter outside at -10°C as long as the temperature drop is not too fast. In the same way, it can adapt to strong heat as long as the rise in temperature is gradual.

This is not the case for the goldfish variety known as "sail tails" or comets, which do not tolerate large temperature changes outside!

Many other varieties have been created by man over the centuries, some of which are only red in name! The most eccentric ones are the lionhead goldfish which are distinguished from the others by protuberances on the top of the head, the telescopic goldfish with exorbitant eyes, the shubukin with very long dorsal and caudal fins, etc. The classic colors are red-orange but many species mix several colors: white and red, golden yellow and white, intense black...

The longevity of goldfish is generally 5 to 10 years on average in aquariums while in outdoor ponds, they can happily exceed 15 years very commonly. Goldfish grow throughout their lives.

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.