Four wings capable of moving independent make the dragonfly an aerobatic ace. This is evidenced by the aerial ballet performed by the couples in the mating season. Portrait of a small helicopter as comfortable in thewater than in the air.
Dragonfly identity card
Already present on Earth 200 million years ago, dragonflies form the order of Odonates, divided into two sub-orders:
- The Zygoptera (also called Demoiselles);
- The Anisoptera.
What differences? Damsels are dragonflies of small size easily recognized by their wings folded. Larger, the Anisoptera display contrasting colors depending on the species and always keep the wings deployed. Nowadays, more than 5000 species are listed worldwide (2800 species of Anisoptera) and about 90 in mainland France, among which we can cite the Emperor Anax, the Depressed Dragonfly, the Scarlet Dragonfly, the Blood-Red Sympetrum, the Four-Spotted Dragonfly, the Reticulated Orthetrum, the Calopetryx gorgeous or the Aeschne Bleue.
Membranous wings and protruding eyes
The flying insect has an elongated body composed of ten segments distinct and protected by an outer shell rigid. The dragonfly has three pairs of legs and two pairs of wings transparent with ribs that always remain open, even at rest. Its round head displays two eyes globular multifaceted, two short antennae and powerful mouthparts crushers. While Odonata often take on a shiny black color, blue or green, there is a huge variety of colors and sizes around the world. The dragonfly is up to 7 cm long for a span can reach 11 cm.
Water: essential element for the dragonfly
The dragonfly is found on all continents except the polar areas where the insect at cold blood could not survive. Its reproduction is inextricably linked to the presence of water points calm where its eggs are laid. Some examples of wetlands it frequents:
- Waters stagnant (lakes, ponds, marshes, bogs, natural and garden ponds);
- Stream at low flow (rivers, streams, backwaters, canals);
- Sources in undergrowth and forests;
- Grasslands and areas flooded.
The mosquito-loving dragonfly
The dragonfly consumes up to a hundredinsects (their larvae and adults) per day. On its menu are the mosquitoes, butterflies, spiders, tadpoles, flies, bloodworms, mayflies or even trichoptera. Its aerial virtuosity makes it a formidable predatory because it flies faster than most of its prey (up to 90km / h top speed), can suddenly change course, reverse or stand still thanks to its four wings which are able to move way independent. The dragonfly deploys two main hunting techniques: the first is to stay on the lookout, perched on a plant, and to seize its target as soon as it is within reach of wings. The second method aims to capture all-comers in flight.
The amorous dragonfly is territorial
Males are found in abundance in breeding grounds in search of a sexual partner and do not hesitate to chase down rivals who would enter on their young. territory. In mating season, dragonflies come out of their solitude usual for mating and it is not uncommon to see pairs flying gracefully in tandem. Depending on the species, the eggs (up to 600) are laid at the area water or inserted into aquatic vegetation. Thehatching occurs after a few days or a few weeks, always depending on the species.
Dragonfly: the long life of the larva
At the anisoptera, the life cycle is punctuated by several stages:
- Theembryo transforms into a prolarva which slips out of the egg to become a larva. This stage lasts a few seconds to a few hours;
- Evolving in water, the larva feeds on zooplankton, infusoria (aquatic microscopic organisms), insect larvae (mainly mosquitoes), tadpoles, even very small fish. It is in the larval state that the dragonfly passes the most long part of life (one to three years or more depending on the species;
- During his growth, the larva will molt up to fifteen times. The succession of moults is explained by the rigidity of its external skeleton that it must leave to develop;
- Become adult or imago, the dragonfly has a longevity varying from a few weeks to several months depending on the species. She usually dies at the end of theautumn.
Dragonfly: several endangered species
According to the International Union for the Conservation of Nature (IUCN), eleven species of dragonflies present in France are threatened with disappearance out of the 90 species identified. Thirteen other species are considered near threatened, among which are the Precious Goddess, the splendid Cordulia and the bluish Agrion. In question ? The destruction of their habitat (through the development of rivers and ponds) and the degradation of quality of water (pollution).
The dragonfly, a gardener’s helper
Just like the ladybug and some birds, the dragonfly plays a role essential within gardens and the environment because it consumes small insects such as mosquitoes and thus helps to to regulate population. You can attract dragonflies to your garden by digging a small body of water (pond, pond) lined with water lilies, rushes and reeds that will promote egg laying. You can also sprinkle your property with plants that she likes: yarrow, echinacea, sage or syngonium. So many small gestures which, on your scale, will help repopulate the nature of this beautiful insect harmless.