A dragonfly is an arthropod with six legs, belonging to the subclass of winged insects, the dragonfly order. The order of dragonflies currently has more than 6650 species of these insects. Dragonflies — these are fairly large predatory insects that have a movable head, large eyes, a long and slender abdomen and four transparent wings. They are found all over the world, with the exception of cold Antarctica.
Origin of the species and description
Odonata or dragonflies — predatory insects belonging to the type of arthropods, a subclass of winged insects and the order of dragonflies. This detachment was first described by Fabricius in 1793. Dragonflies are a very numerous order, which includes 6650 species. 608 species are currently classified as extinct species, and 5899 species of these insects inhabit our planet in modern times.
The dragonfly order is divided into 3 suborders:
Dragonflies are a very ancient group of insects. The first dragonflies inhabited the earth as early as the Carboniferous period of the Paleozoic era. These insects are descended from giant dragonfly-like insects called meganeur. Meganeurs were large insects with a wingspan of up to 66 cm. These insects were considered the largest insects of ancient times. Meganeurs later gave birth to the following groups of their descendants: Kennedyina and Ditaxineurina, these groups of insects lived in the Triassic period of the Mesozoic era. They were large, the wings of these insects were about 9 cm long. During rest, they folded under the abdomen of the insect.
The insect also developed a trapping basket used for grasping prey. During the Jurassic, the following groups came: Lestomorpha and Libellulomorpha in these insects, the larvae developed in the aquatic environment and they had an improved aircraft. Insects of the Libellulida group inhabited Africa, South America and Australia during the Triassic period. Meganeuri still lived in Eurasia at that time, but in the course of evolution their bodies and habits changed. In the Jurassic period, meganeurins reached the pinnacle of evolution and populated the whole of Eurasia. These insects had «trapping basket», they could use it to hunt during the flight. Gas exchange in this group was carried out with the help of the respiratory epithelium, but there were also lamellar gills, which changed over time, ceased to perform a gas exchange function and were replaced by internal gills.
At the same time, the descendants of the Calopterygoidea family strongly evolved from the initial state. The wings of these insects narrowed, became stalked and the size of the wings became the same. In the Jurassic, insects of the suborder Anisozygoptera become the most common, the number of which sharply decreases during the Cretaceous, but this group remains widespread throughout the entire polygenic period. During this period, such species of dragonflies as Coenagrionidae, Lestidae and Libelluloidea, etc., almost disappear. The Cenozoic fauna is already inhabited by modern species of dragonflies. During the Neocene, the ethnofauna is no different from the modern one. The population of Zygoptera has declined sharply, but Coenagrionidae and Lestidae have become the most common species.
Appearance and Features
All dragonflies have a very recognizable appearance. The color of these insects can be different.
In the body of the insect stands out:
- head with large eyes;
- brightly colored shiny body;
- transparent wings.
These insects, depending on the species, can be of different sizes: the smallest dragonflies are 15 mm long, and the largest are about 10 cm long. The head is large and can rotate 180°. On the head of a dragonfly there are eyes, which consist of a large number of ommatidia, their number ranges from 10 to 27.5 thousand. The lower ommatia can only perceive colors, while the upper ommatia can only perceive the shapes of objects. Thanks to this feature, the dragonfly can navigate well and easily find prey. The parietal part is swollen, three ocelli are located on the crown of the head. The antennae of the dragonfly are short, subulate, consisting of 4-7 segments.
The mouth is powerful, formed by two unpaired lips — top and bottom. The lower lip consists of 3 lobes and covers the powerful lower jaws. The upper has the form of a short plate, which is elongated in the transverse direction, it overlaps the upper jaw. The lower lip is larger than the upper one, thanks to which the insect can chew its prey during the flight.
The chest consists of 3 sections: prothorax, metathorax and mesothorax. Each part of the chest has a pair of limbs, and insect wings are located on the middle and back parts. The front is separated from the middle. The middle and posterior parts of the chest are fused and form a synthorax, which is perceived as the chest. The shape of the chest is flattened from the sides, the part of the chest located on the back is pushed back. The mesothorax is located higher than the metathorax, due to which the wings are intertwined behind the legs. The pronotum is divided into 3 lobes, the middle lobe usually has an indentation. The segments on which the wings are located are hypertrophied pleurites.
The wings are transparent, consist of two chitinous layers, each of them is formed by its own system of veins. These veins overlap each other, so the network of them seems to be one. The venation is complex and dense. Different orders of these insects have different venation systems.
The abdomen of a dragonfly is mostly rounded and elongated. In rare species, it is flat. The abdomen makes up the majority of the insect’s body. Consists of 10 segments. On the sides are pleuritic membranes that allow the dragonfly to bend. All segments except 9 and 10 have one sigma. At the end of the abdomen there are 2 anal appendages in females, 3-4 in males. In females, the genitalia are located at the end of the abdomen, in males, the compiling organ is located on the 2nd segment of the abdomen, the vas deferens is located on the tenth segment of the abdomen. The limbs are strong and developed and consist of: thigh, coxa, lower leg, vetlug, paws. There are spines on the limbs.
Where does the dragonfly live?
Dragonflies are widespread throughout the world. These insects cannot be found, probably only in Antarctica. A special variety of species of these insects can be found in the Indo & # 8212; zone. About 1664 species of dragonflies live there. There are 1640 species in the neotropics. And also, dragonflies like to settle in the Afrotropic, about 889 species live there, in the Australian region about 870 species.
In countries with a temperate climate, fewer species of dragonflies live, this is due to the thermophilicity of these insects. There are 560 species in the Palearctic and 451 species in the Nearctic. For life, these insects choose places with a warm and humid climate. The presence of a reservoir is very important for dragonflies; during the mating season, the female lays eggs in the water, eggs and larvae develop in the aquatic environment. Depending on the species, dragonflies have different attitudes towards the choice of water bodies and the need to live near water. For example, dragonflies of the species Pseudostigmatinae are content with small water reservoirs of the undergrowth. They can use small ponds, lakes or flooded pits for breeding. Other species settle near rivers, ponds and lakes.
The larvae spend their lives in the water, and adults, having learned to fly, can fly long distances. Found in meadows, forest edges. Dragonflies are very fond of soaking up the sun, it is very important to them. With the onset of cold weather, dragonflies fly to countries with a warmer climate. Some dragonflies fly up to 2900 km. Sometimes dragonflies migrate in particularly large numbers. Flocks numbering up to 100 million thousand individuals were noted. But more often, dragonflies do not stray into flocks, but fly alone.
Now you know where the dragonfly is found. Let’s see what it eats.
What does a dragonfly eat?
Dragonflies are predatory insects. Adults feed on almost all types of insects inhabiting the air.
The diet of dragonflies includes:
- flies and midges;
- small fish;
- other dragonflies.
Dragonfly larvae feed on mosquito and fly larvae, small crustaceans, and fish fry.
According to the methods of hunting, these insects are divided into several subspecies:
- free hunters who hunt in the upper tier. This group includes species of dragonflies with powerful and developed wings that can fly well and quickly. These species can use pack hunting, but more often hunt alone at a height of 2 to 9 meters above the ground;
- free-flying predators hunting in the middle tier. These dragonflies hunt at a height of up to 2 meters. They are always in search of food, for rest they can sit on the grass for a few minutes, and then begin to hunt again;
- dragonflies lie in wait. This species is distinguished by its unusual way of hunting. They sit quietly on the leaves or stems of plants, looking out for prey, breaking off from time to time to attack;
- dragonflies living in the lower tier. These dragonflies hunt in thickets of grass. They slowly flit from one plant to another in search of insects that sit on the plant. This species eats prey sitting on a plant, and does not eat while flying.
Interesting fact: Cannibalism is very common among all species of dragonflies. Adult dragonflies may eat smaller dragonflies and larvae. Sometimes females after mating can attack the male and eat him.
Character and Lifestyle Features
In our country, dragonflies live from late April to October. In warm and tropical countries, these insects live all year round. Dragonflies — diurnal insects. They are most active in sunny and warm weather.
In the morning, dragonflies try to bask in the sun, sitting on stones or pieces of wood. During the midday heat, they take the position of «reflection», in which the luminous tip of the abdomen is directed towards the sun. This reduces the effect of sunlight on the body of the insect, and helps to avoid overheating.
Interesting fact: Dragonflies practically do not use their legs for movement, they are used only during takeoff and landing. The rear pair of limbs is used to capture prey.
Dragonflies go hunting in the morning and evening. Some species are more active at dawn. In the daytime, dragonflies are busy procreating. At night, insects hide among thickets of foliage and grass. Dragonflies are mostly solitary.
Interesting fact: Due to the structure of the wings, dragonflies can fly very fast, make interesting turns in the air, and migrate over long distances. Due to the fact that dragonflies are well versed in the art of flight, they are very difficult to catch by predators.
Social structure and reproduction
These insects go through three stages of metamorphosis:
- naiads or larvae;
- adult insects (adults).
Many dragonflies are able to produce more than one offspring per year. Insects mate right in the air. Before mating, the males perform a kind of ritual dance in front of the female. They fly around her, doing strange things in the air. Females after mating lay from 260 to 500 eggs. The reason for the death of eggs is eating them by other creatures, including dragonflies.
Also, water pollution, or a decrease in air temperature. In favorable conditions, the larvae hatch from the eggs in a couple of days, but often in temperate climates, the larvae do not appear until the following spring.
Interesting fact: Dragonfly eggs can overwinter unchanged and the larvae will hatch next spring.
Egg hatched only, larva size — 1 mm. At this stage, the larva lives only a few minutes, then it begins to molt. Depending on the subspecies, the larvae develop at different times and undergo a different number of molts. The larvae are able to feed on their own and lead an underwater lifestyle.
Usually, the larvae are inactive, burrow into the ground or hide among the algae. Dragonfly larvae feed on larvae of mosquitoes and other insects, fry of small fish and crustaceans.
Natural enemies of dragonflies
The main enemies of dragonflies are:
- predatory fish;
- orb-web spiders, hobo spiders and tetranatids;
- carnivorous mammals.
Eggs and small larvae are eaten by fish, crustaceans, and other larvae. Most of the eggs die without hatching, being eaten by predators or being prevented from developing by adverse weather conditions. In addition, dragonflies often parasitize sporozoans. Trematodes, threadworms and water mites. Because of their lifestyle, dragonflies are also often preyed upon by insectivorous plants.
Dragonflies are very nimble insects that fly quite quickly. In the daytime, they can disguise themselves under the reflections of the sun, sitting on plants or trees with their belly down, their transparent wings are hardly visible to many predators, and this disguise allows dragonflies to circle the enemy around their fingers.
In addition, dragonflies fly masterfully, and it is very difficult to catch up with a dragonfly, the only option for a predator is to feast on this insect — is to take her by surprise. Larvae, defending themselves from predators, try to burrow into the ground, or hide in algae. Larvae swim very rarely, although they are very good at it.
Species population and status
The population of the order Odonata is numerous and diverse. There are more than 6650 species of these insects in the world. These insects are found on all continents and migrate. Many species of these insects live well and breed in the wild. However, today some species of dragonflies are on the verge of extinction and their populations are rapidly declining. This is due to human pollution of dragonfly habitats.
A number of species are listed in the Red Book. At the end of 2018, more than 300 species are listed in the Red Book. Of these, 121 species are on the verge of extinction, 127 subspecies have the status of insects in a vulnerable position, and 19 subspecies are already extinct. The species Megalagrion jugorum is considered extinct. In the global population, in general, about 10% of all species of dragonflies are on the verge of extinction.
Dragonflies are a very important group that indicates the state of water bodies, as dragonfly larvae react strongly to any changes in water quality. Dragonfly larvae die in polluted reservoirs. In order to maintain the population of these insects, it is necessary to take better care of the environment. Install cleaning equipment at enterprises, create protected areas in the habitats of dragonflies.
Dragonflies have a very important role in the ecosystem. These insects destroy blood-sucking insects that carry various diseases. Dragonfly larvae are food for many species of fish, while birds, mammals and spiders feed on adult insects.
In addition, dragonflies are excellent indicators of the ecological situation, since dragonfly larvae cannot develop in polluted water. Today, many species of these insects are listed in the International Red Book for tracking populations. They are taken under special protection.
A dragonfly conservation society has been created, which monitors the number of populations of these insects. With the development of new territories by humans and the advent of urbanization, the dragonfly population began to decline. This is due to the draining of reservoirs by people, the construction of enterprises, roads and cities.
Dragonfly — very beautiful and amazing insect. Watching these creatures is very entertaining. We must be more environmentally friendly in order to preserve the diversity of these insect species.