BI-WINGERS(Diptera), an order of insects characterized by the presence of one pair of wings. This is one of the largest and most widespread groups of insects, including approx. 100,000 species. It includes such well-known species as houseflies, mosquitoes, midges, midges, horseflies and gadflies.
Flight behavior. Although large swarms of Diptera are often observed, they are not social insects such as termites, bees and ants. On the contrary, most of them live alone, at least for most of their lives. However, many dipterans gather in a kind of swarms, attracted by the smell of food, convenient place for rest or mating.
Clusters. Diptera can fly to the light together with insects of other species. Mosquitoes, bells and centipedes swarm closer to dusk, usually over bushes, paths or other landmarks, near which the swarm, if frightened off, gathers again. Such groups consist mainly of males; It is believed that the sound of their wings attracts females with their characteristic tone. In experiments, by producing sounds similar to the squeaking of female mosquitoes of certain species, it was possible to induce swarming of the corresponding males. Clusters are especially characteristic of blood-sucking dipterans (gnus). If a species is active mainly in the dark, it is called nocturnal, if in the light it is called diurnal; An intermediate crepuscular group is also distinguished.
« Hanging» flight observed in different types dipterans, but is especially developed in hoverflies and buzzers. Representatives of these families fly quickly and maneuver well in the air. You can often observe how they hover motionlessly in place, intensively working their wings, and then suddenly disappear from view.
General characteristics. In the vast order of Diptera there is a huge variety of body sizes, shapes and colors. The length of some gall midges is only 0.4 mm with a wingspan of just over 1 mm. Australian blackbirds reach a length of 50 mm, and the wingspan of individual tropical centipedes exceeds 100 mm.
However, despite the large number of species and diversity of dipterans, they all share common characteristics. Typically, adults have only one pair of membranous wings, rather thin integuments, 5-segmented tarsi, a licking or sucking mouthpart (proboscis) and well-developed compound (compounded) eyes. Development occurs with complete transformation (metamorphosis), i.e. a larva hatches from the egg, which, after several molts, turns into a motionless pupa, and from the pupa an adult insect (imago) is born. Diptera larvae, unlike caterpillars, are always legless.
The general structure of dipterans is the same as that of other insects. The body of the imago consists of three main parts. The head bears the mouthparts, eyes and antennae. The chest includes three segments with three pairs of walking legs and a pair of wings (their second pair, the posterior one, has turned into halteres). Almost all the space inside the chest is occupied by powerful muscles necessary to activate the locomotor organs. The abdomen consists of a varying number of externally expressed segments (depending on the species) and contains the reproductive organs and most digestive system.
| EXTERIOR STRUCTURE OF A HOUSE FLY |
Head. Oral apparatus. Although dipteran adults use a wide range of food sources, their oral apparatus is essentially always a sucking or licking proboscis, sometimes so hard and sharp that they are capable of piercing the skin of many vertebrates or the integument of other insects. Many dipterans, including the housefly, can often be seen with their soft proboscis extended and attached to various wet surfaces. In contact with the substrate are two extended lobes of the lower lip, or oral discs, adapted for the absorption of liquid food. Numerous thin channels (pseudotrachea) on their underside converge at the central point of the proboscis, from where liquid is drawn into the head using a bellows-like pharyngeal pump.
Horseflies not only possess licking structures, but also two pairs of hard, dagger-shaped appendages—modified upper and lower jaws—for piercing the skin of the animals whose blood they feed on. Even their upper lip turned into a stiletto and became integral part piercing oral apparatus. (However, male horse flies do not feed on blood, and their lower jaws are reduced.)
In mosquitoes, the lower lip does not take part in feeding, but serves only as a case for the needle-shaped stiletto jaws, which fold into a thin piercing proboscis. When these jaws penetrate the body of a vertebrate, it bends and remains on the surface. The upper lip of mosquitoes (and some other bloodsuckers, such as midges, midges and tsetse flies) is also part of the piercing mouthparts. A groove runs along its lower (posterior) side, covered by another part of the oral apparatus - a long tongue, or hypopharynx. It is pierced by a channel through which saliva is supplied to the victim's wound. The mosquito absorbs the blood diluted with it through a tube formed by the upper lip and hypopharynx.
Antennas
(antennae, or cubs) of dipterans are quite diverse in shape, which is widely used to classify these insects. It is believed that their oldest species had long multi-segmented antennae, like modern mosquitoes and centipedes, the antennae of which consist of two thick basal segments and a whip-like part formed by thin, more or less cylindrical segments numbering from two to 39. In the more advanced in evolutionary terms Diptera antennae are usually formed by two basal segments and a third - thickened, of various configurations. It often bears at the end or dorsal side a thin appendage formed by the fusion of many segments - glabrous or pubescent, bristly or ringed.Breast insects consists of three segments: prothorax, mesothorax and metathorax. Since the main part of the pectoral muscles is responsible for flight, the middle segment, which carries the wings, is usually noticeably larger than the other two.
Legs attached to the chest, with each segment carrying one pair of them and containing the corresponding muscles. Like other insects, the typical Diptera leg consists of five parts: coxa, trochanter, femur, tibia, and tarsus. The terminal part (tarsus) is usually formed by five segments and ends with a pair of claws. Under each claw there is a soft glandular pad. The claws help move along rough surfaces. When walking, the soft pads are compressed and secrete an adhesive secretion, allowing the dipterans to hold on even where there is nothing to cling to.
Wings. Most insects have two pairs of wings, but in dipterans one of them (the posterior one) is transformed into small club-shaped appendages, the so-called. halteres. Individuals in which they are damaged or removed partially or completely lose the ability to fly. The halteres are movably articulated with the sides of the metathorax and vibrate in the vertical plane with the same frequency as the wings, but in antiphase with them. With the help of mechanoreceptors located at their base, they give the insect the opportunity to determine and correct balance in the air.
Thin membranous wings are strengthened by cylindrical veins. Diptera have fewer of them than most other insects, and there are especially few transverse veins. Wing venation is a very important classification feature used to divide an order into lower-ranking taxa. Near the base of the wing, on its posterior (inner) edge, there may be a notch that separates a small lobe or scale from the main plate.
Abdomen primitive dipterans are elongated, almost cylindrical and consist of 10 segments, of which the two closest to the chest are very indistinctly separated from each other. In more specialized families, the number of visible abdominal segments is smaller, in particular, it has been reduced to 4 or 5 in the housefly and its closest relatives. Shortening, the abdomen becomes closer in shape to a cone or even a sphere.
Reproductive system. The only visible abdominal appendages are the copulatory organs in males and the ovipositor in females. The latter is usually tubular or saber-shaped. In males, the expanded last segment bears special grips that serve to hold the female by the ovipositor during mating. The internal genital organs, located in the abdomen, consist of gonads (testes in males and ovaries in females), accessory glands that secrete liquid secretions, and excretory ducts. The shape of the external genital appendages in Diptera varies widely. The structure of the copulatory “captures” in males serves as the main taxonomic character in determining the species of some families.
Digestive system. The abdomen contains most of the digestive system, mainly the intestines, sometimes forming blind outgrowths. The excretory organs are the Malpighian vessels - long thin tubes that open into the intestines. In the front part of the abdomen there is a goiter - a thin-walled sac connected by a narrow tube to the esophagus. The crop serves as a temporary reservoir for liquid food. Filling with air, it probably facilitates the emergence of an adult insect from the pupa shell.
Diversity. Sexual dimorphism. One of the surprising phenomena that is often found in Diptera is sexual dimorphism, i.e. significant differences in appearance between males and females of the same species. For example, as noted above, the males of many species have holoptic compound eyes, i.e. touch each other, whereas in females they are separated by a frontal stripe (dichoptic). In female mosquitoes, the antennae are sparsely pubescent, while in males they are densely covered with long hairs. Sexual dimorphism can also be expressed in size: males are usually smaller. In females of some species, the wings are absent or greatly reduced, while in males they are normally developed. In one of the families of Diptera, in females, two veins of the wing merge at its edge, and in rare males they are separated along the entire length. In another group, the legs, antennae, or other body parts of males often bear tufts of hairs with a metallic sheen that are absent in females. The legs of the males of some mosquitoes are trimmed with a wide scaly fringe; females do not have it. Differences in coloration between the sexes are common, but usually not noticeable. However, sometimes this difference is quite significant; for example, males of one American centipede are pale reddish, while females are almost black.
Mimicry and protective coloration. Many species of harmless dipterans are strikingly similar in appearance to other insects, especially bees and wasps, which humans and probably other animals try to avoid. This phenomenon is called mimicry. A typical example of this is the appearance of a number of hoverflies; they are so similar to wasps that even an entomologist will not always immediately correctly identify the insect. Other hoverflies mimic the appearance of bees. Some flies are more or less like bumblebees. This similarity is reflected in the nomenclature of dipterans: the entire family Bombyliidae (buzzers) is named in Latin after bumblebees ( Bombus); there are bee-like hoverflies, bumblebee hoverflies, hornet-shaped moths, etc.; one of the clans of ktyrs is called Bombomima (“bumblebee imitator”).
Some dipterans avoid predators with the help of protection, i.e. camouflage, coloring. The dark color of fungus gnats makes them invisible as they sit motionless in crevices under fallen trees. Other dipterans have “dismembering” coloration. For example, in liriopids, bright black and white stripes on the body are arranged in such a way that these insects, flying against a light or dark background, simply look like sets of spots that do not form a single whole.
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| FOUR STAGES OF THE LIFE CYCLE common housefly. A - The egg of a housefly is laid on the surface of a food substrate, such as a garbage heap. b- A whitish, relatively inactive larva (maggot) hatches from the egg. V- After a period of feeding and growth, accompanied by two changes of skin (molting), the larva pupates inside its skin, which hardens and turns brown, turning into the so-called. pupary. At the pupal stage, the organs of an adult insect (imago) are formed. G- An adult fly emerges from the puparium, spreads its wings and flies away. The egg, larva, puparium and young adult are shown enlarged to the same scale. |
Like other higher insects, life cycle Diptera are complex and involve complete metamorphosis. The eggs of most species are oblong and light-colored. They hatch into larvae that are usually elongated, roughly cylindrical, soft-bodied and legless. In most cases, the hard parts of their heads are greatly reduced; Such worm-like larvae are called maggots. The larva feeds intensively and periodically molts as it grows. The number of larval molts varies among dipterans, but usually there are two or three. This is followed by the pupal stage. In some dipterans it is formed inside the larval skin, which turns into the so-called. "puparium". Eventually the shell of the pupa ruptures, and an adult insect (imago) is born.
Life cycle of a housefly. Using the example of the housefly, we can trace the development of dipterans. To lay eggs, the female searches for accumulations of decaying organic matter, such as manure or garbage heaps. Thus, the fly instinctively leaves the clutch where the sedentary larva will be provided with a sufficient amount of food. At one time, the female can lay 120 or slightly more narrow whitish eggs of approx. 1 mm long. Huge masses of them are found in places where several females leave their clutches at the same time. At summer temperatures of 24-35° C, egg development takes approx. 8 ocloc'k. The worm-like larvae that hatch from them are approx. 2 mm begin to feed voraciously. They grow so quickly that the first moult occurs after 24-36 hours, and the second about a day later. The third stage larva feeds for another 72-96 hours and grows to a length of approx. 12 mm and then pupates.
An oblong pupa forms inside the last larval skin, which becomes the pupal case (puparium). This shell changes its dirty white color to brown and hardens. Within 4-5 days, inside the apparently inactive pupa, the larval tissues disintegrate and rearrange themselves, forming the structures of an adult insect. In the end, the imago comes out with the help of a special frontal bladder, which, under the pressure of “blood” (hemolymph) pumped into it, protrudes into the frontal part of the head. Under its pressure, the “lid” of the puparia opens, releasing the adult insect. It crawls out of the decaying debris or soil in which it pupated, spreads its initially crumpled wings and flies off to feed and mate, starting a new life cycle.
Another curious form of reproduction found in some dipterans is pedogenesis, i.e. the appearance of offspring in apparently immature individuals. Thus, in gall midges, an adult female lays only 4 or 5 eggs, from which large larvae are formed. Inside each of them, from 5 to 30 (depending on the species and individual) daughter larvae develop. They feed on the mother's body and then reproduce themselves in the same way. After several such cycles, successive larvae pupate, and a generation of adults is formed. Larvae reproduce without mating. This development of unfertilized eggs is called parthenogenesis. This phenomenon, in the absence of pedogenesis, has been found in other dipterans, for example, in some midges. Females lay unfertilized eggs, which only hatch into females. Parthenogenesis can be cyclic, constant or sporadic. Cm. REPRODUCTION.
There is, perhaps, no corner on land where dipterans do not live. This is the most widespread order of insects, although the ranges of many of its families are not fully known. Each of the large zoographic regions is characterized by its own set of taxa, but the genera and families to which they belong can be cosmopolitan, i.e. meet almost everywhere. About two dozen species of Diptera are also cosmopolitan. About half of them were unwittingly dispersed throughout the planet by humans. These species include the ubiquitous housefly, the squeak mosquito ( Culex pipiens), the gastric horse botfly and the autumn fly. Among approximately 130 families of Diptera, less than 20 are truly cosmopolitan, although the ranges of many others are not much narrower, i.e. they are distributed subcosmopolitanly.
Diptera abound in the humid tropics. The distribution of most families is limited to this natural zone, while many others reach their maximum diversity and abundance here. In temperate or cold areas, it occurs per unit area fewer species dipterans, but the number of their individuals is often no lower than in the tropics. In the windswept arctic desert, on the mountain tops and among the dunes, where the harsh climatic conditions are not suitable for most insects, Diptera remain the most prominent representatives of this group of invertebrates. In the north of Greenland, several hundred kilometers from the North Pole, there are centipedes, carrion flies, flower flies, bell flies and fungus gnats. On the other side of the Earth, on the Antarctic islands, there are several species of midges, hoverflies, centipedes, gall midges and some other groups. In Antarctica itself, only one species of wingless mosquitoes has so far been recorded, but it is likely that other dipterans will be found there.
Diptera mainland islands are usually close to those living on the nearest continents, but on more isolated oceanic islands they, even belonging to widespread groups, are often very peculiar. Apparently, a single, accidental arrival of some species on such islands in the distant past led in the course of evolution to the appearance of a whole set of diverse forms. This may explain, for example, the fact that almost a third of Hawaii's 246 dipteran species belong to just one family.
Having thin integuments, most dipterans are not able to effectively retain water in their bodies. They would constantly be in danger of drying out if they did not live in more or less humid conditions. Although larvae in many cases lead an aquatic lifestyle, adults are almost always terrestrial. The only exception is sea centipedes Limonia monostromia, whose entire life cycle takes place in warm sea waters off the coast of Japan.
Larvae. The habitats of dipteran larvae are much more diverse than those of adults and include almost all types of ecological niches. Some attack aphids or nibble the leaves of mosses and other plants, i.e. live openly. However, in most cases they develop in the thickness of a moist substrate, for example inside the leaves, stems and roots of plants. Larvae of many species make tunnels in rotting wood, fungi or soil, feeding on organic debris or microscopic invertebrates.
They often live in standing and flowing bodies of water of any size, where they feed on vegetation, microorganisms or insects of other species. Most of these aquatic larvae prefer shallow places, but in some bell mosquitoes they dive to a depth of more than 300 m. If their development requires a good supply of oxygen, they attach to the stones of river rapids or mountain streams. The larvae and pupae of some dipterans prefer water with a high content of alkalis or salts, and in one Californian species they live in oil puddles. Others are found in hot springs and geysers, where the water temperature reaches 50 ° C. The larvae of one of the mosquitoes survive even in the liquid filling the pitcher leaves of insectivorous plants, where other insects drown and are digested.
Judging by fossil finds, insects existed already in the Devonian period, i.e. OK. 300 million years ago. However, until the Upper Triassic (about 160 million years ago), no remains of dipterans were found among them. The most primitive representatives of this order are similar to centipedes and are united in the extinct family Architipulidae. Many different dipterans, close to modern forms, are found in Baltic amber - the resin of coniferous trees, fossilized in the Upper Oligocene, i.e. about 35 million years ago. The Miocene shales from Florissant, Colorado, contain many fossils of centipedes, fungus gnats, and other dipterans characteristic of marshy habitats. Among them, even the tsetse fly is noted, although at present this genus is found only in Africa. The study of Baltic amber and Florissant fossils showed that by the middle of the Cenozoic era, dipterans had passed through most of their evolutionary development.
Many dipteran species are best known as disease vectors, nuisance bloodsuckers, and crop pests. Chemical methods of combating them are the most effective, but even the newest insecticides cannot be considered a panacea, since insects quickly become resistant to them.
Vectors of human diseases. Listed below are just a few of the medically important dipterans.
Housefly mechanically transports pathogens of bacterial dysentery; it is possible that it can also spread the bacteria of typhoid fever, paratyphoid fever, cholera and the polio virus.
Horseflies can transmit from an infected animal the causative agents of tularemia, as well as one of the filariasis - loiasis.
Cereal flies from the family Hippelates When feeding near the eyes, they easily introduce bacteria into them, causing acute epidemic conjunctivitis.
Blood sucking. Blood-sucking dipterans, even if they are not carriers of diseases, such as biting midges, autumn flies, many mosquitoes and midges, when attacked en masse, worsen human health, causing itching and allergic reactions, sharply reducing performance. In addition, all of these species remain potential spreaders of pathogenic agents.
Pests of agricultural plants. Compared to beetles, butterflies, herbivorous bugs and representatives of some other orders of insects, dipterans cause relatively little damage to agricultural plants. Representatives of only 5-6 families have a certain significance in this sense. The Hessian fly from the gall midge family is a serious pest of grain crops. This species mainly damages wheat, but is also dangerous for barley and rye. Hessian fly larvae feed on plant sap at the base of stems, causing stunted growth and lodging. With the development of wheat varieties resistant to this attack, the importance of this agricultural pest has decreased. The variegated fly family includes many species that feed on the succulent fruits of various plants, but only a few of them cause serious damage. Thus, apple moth larvae spoil apples, damage citrus fruits and other fruits. fruit trees, significantly reducing the yield. The larvae of other dipterans gnaw tunnels in various plants. As an example, we can cite three species from the flower family: sprouts, spring cabbage and onion flies. Representatives of the family of cereal flies, living in many parts of the world, damage grain crops.
The order Diptera (Diptera) is divided according to different systems, into 121-138 families, which are grouped into two or three suborders. When classifying, the most commonly used characters are the venation of the wings, the length of the antennae and the number of segments in them, the number and location of bristles and spines on the body and legs, the configuration of the external genital appendages, the presence or absence of simple ocelli and the shape of the hole through which the imago leaves the pupal skin or puparia. Coloring, size and shape of the body do not always allow us to judge the degree of relationship, because natural selection often leads to external similarities between representatives of very distant groups. The diagram below, which includes only the most important families, is just one of possible ways classification of approximately 100 thousand species of Diptera; the number of species in families is indicated approximately.
Suborder Nematocera (long mustache). These insects are characterized by long antennae with more than three segments. The group includes 36 families. The antennae of the imago consist of 6 or more approximately identical, movably connected segments, and the mandibular palps usually consist of 4 or 5. The larvae have a well-developed dark-colored head capsule. The pupa is not enclosed in a larval skin, i.e. no puparia is formed.
Tipulidae (centipedes): 10,000 species, cosmopolitan.
Psychodidae (butterflies): 400 species, subcosmopolitan.
Chironomidae (bellers, or jerks): 2000 species, cosmopolitan.
Ceratopogonidae (biting midges): 1500 species, subcosmopolitan.
Culicidae (true mosquitoes): 1600 species, cosmopolitan.
Mycetophilidae (fungus gnats): 2400 species, cosmopolitan.
Cecidomyiidae (gall midges): 4500 species, subcosmopolitan.
Bibionidae (centipedes): 500 species, mainly in Eurasia and North America.
Simuliidae (midges): 600 species, subcosmopolitan, but especially numerous in Eurasia, North and South America.
Blepharoceridae (reticulate wings): 75 species, found in highlands.
Suborder Brachycera (short-whiskered) includes approximately 100 families. The antennae of adult insects consist of three segments, of which the last (distal) is thickened and bears an appendage in the form of a seta or rod on the dorsal side or apex. Palpi of one or two segments. The head of the larva is poorly formed or rudimentary. Representatives of some families (straight-suture) have a free pupa; in other cases (round-suture dipterans) it develops inside the puparia.
Tabanidae (horseflies): 3000 species, mainly in the tropics and subtropics.
Stratiomyiidae (lion flies): 1500 species, subcosmopolitan.
Rhagionidae (snipe): 500 species, mainly in North America and Eurasia.
Nemestrinidae (long-proboscideans): 250 species, subcosmopolitan, but mainly in Central and North Africa.
Bombyliidae (buzzers): 2000 species, subcosmopolitan, but mainly in North America and the Mediterranean.
Asilidae (Ktyri): 5000 species, subcosmopolitan, but most diverse in the tropics.
Mydaidae: 200 species, distributed in many but isolated regions.
Dolichopodidae (greenfinches): 2000 species, cosmopolitan.
Empididae (pushers): 3000 species, mainly in Eurasia, North and South America.
Phoridae (humpbacks): 1000 species, mainly in the tropics.
Platypezidae (fungus flies): 100 species, mainly in Eurasia and North America.
Pipunculidae: 400 species, mainly on the northern continents.
Syrphidae (hoverflies): 4000 species, subcosmopolitan.
Conopidae (bigheads): 500 species, subcosmopolitan.
Ortalidae (spot wings): 1200 species, cosmopolitan, but especially abundant in the tropics.
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AVERAGE LENGTH OF BI-WINGERS, MM |
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| Buzzed | |
| Bighead | |
| Midge | |
| Lacewing | |
| Hessian fly | |
| Gadfly gastric | |
| Bullfly | |
| Sheep fleece | |
| Mosquito | |
| Spotwing | |
| Ktyr | |
| Gadfly subcutaneous | |
| Hoverfly | |
| Ezhemukha | |
| American Meromisa | |
Trypetidae (pied wings): 2000 species, mainly in the tropics and subtropics.
Sciomyzidae (tentails): 200 species, mainly in the northern continents and southeast Asia.
Drosophilidae (fruit flies): 750 species, subcosmopolitan.
Ephydridae (shorebirds): 800 species, mainly in Eurasia and North America.
Chloropidae (cereal flies): 1200 species, cosmopolitan.
Agromyzidae (mining flies): 1000 species, cosmopolitan, but especially abundant in Eurasia.
Anthomyiidae (flower girls): 3000 species, cosmopolitan.
Calliphoridae (carrion flies): 500 species, subcosmopolitan, but mainly in the Northern Hemisphere.
Sarcophagidae (gray blowflies): 1000 species, subcosmopolitan but mainly in the tropics.
Muscidae (true flies): 150 species, cosmopolitan.
Tachinidae (jermules): 5,000 species, cosmopolitan but most diverse in the tropics.
Oestridae (nasopharyngeal botflies): 150 species, subcosmopolitan, but mainly in warm areas.
The order Diptera includes insects, the most characteristic feature of which is the presence of one, front pair of wings (rarely there are no wings at all). In place of the second, posterior pair there are halteres, small mobile appendages of the metathorax. These peculiar club-shaped organs are preserved, with rare exceptions, in wingless forms, which makes it possible to easily identify such insects to the order.
The size of the imago varies greatly - some species reach 30-50 mm in length, while others do not exceed 1 mm in length. There are two main types of body structure of Diptera. Insects with a narrow abdomen, long legs and long multi-segmented antennae are called mosquitoes, and those with a relatively wide abdomen, short legs and short three-segmented antennae are called flies. The large eyes, located on the sides of the head, can touch on the forehead, especially often in males, while in females they are usually separated by a frontal stripe, although in some families (for example, buzzers) touching eyes are characteristic of both males and females. The antennae, or antennae, are attached to the front of the head, and not at the top, as in most insects of other orders. In mosquitoes they are multi-segmented (more than 6 segments), in flies they are three-segmented. An intermediate type between polysegmented and three-segmented is the antennae, in which the third segment is divided into several rings, the so-called annular segment. In flies, the third (last) segment often bears a special appendage (aristu) in the form of a stick or bristle. The arista may be located at the apex of the third segment or on its dorsal surface; usually it is two- or three-membered. The oral organs of dipterans are a proboscis, long or short, thin or thick, soft retractable or hard non-retractable. Based on the method of eating, two types of proboscis are distinguished. The first type is piercing-sucking, like blood-sucking mosquitoes, the second is licking-sucking, like a housefly. In both the first and second cases, various kinds of changes in the structure of the proboscis are possible, and then, for example, a cutting-sucking proboscis appears, like in a horsefly, or a drilling proboscis, like in a blood-sucking burner fly.
The thoracic region consists of three rings tightly fused together. The prothorax and metathorax in most dipterans are not wide, sometimes barely noticeable when viewed from above. Almost the entire dorsal surface of the chest is occupied by the largest mesothorax. And this is quite understandable, since the only pair of wings in dipterans is attached to it, and it contains wing muscles. The wings themselves are membranous, glassy-transparent, sometimes smoky or brownish or with different dark pattern in the form of spots or stripes. The wings have a well-developed system of longitudinal veins or their derivatives. The number of cross veins is small. Features of wing venation are important in determining families and genera. When identifying many groups of dipterans, the location on the body and the number of some setae are no less important. The abdomen consists of 4-10 visible segments. The terminal segments of the male's abdomen are transformed into a complex reproductive apparatus. Females of a number of families have a rather long, clearly visible sclerotized ovipositor; in many flies, the last segments of the abdomen form a retractable (telescopic) ovipositor.
Diptera are one of the largest order in terms of the number of species (there are over 200,000 of them in the world fauna). Many families (approximately 100 of the 180 members of the order) are found on all continents except Antarctica. About 40 families are distributed on no more than two continents. And only a small part of them is represented by species that are sharply limited in their distribution - typical endemics. Diptera appeared in the geological record of the Earth in the Mesozoic. The oldest imprints of their wings date back to the Triassic. The evolution of the order proceeded at such a rapid pace that already in the Paleogene the Diptera fauna was in many ways similar to the modern one.
Diptera have complete metamorphosis. Their life cycle consists of the stages of egg, larva (several instars), pupa and adult insect, or adult. Most adult dipterans gravitate in our latitudes to temperate and even high humidity. For this reason, they prefer to stay in thickets of bushes, among the herbs of meadows, and along the banks of reservoirs. Only some families have developed adaptations to life in arid landscapes.
Many flies and mosquitoes are excellent flyers, capable of covering considerable distances (sometimes up to several tens of kilometers).
Small species rise when settling by air flows high above the ground and move to long distances together with air masses, forming a noticeable group of aeroplankton. Many dipterans have not only the ability to fly long distances, but also high flight speed (some horseflies reach speeds of up to 60-70 km/h) and excellent maneuverability. There are no equals to the hoverflies, which are capable of hovering in the air for a long time, making throws forward, sideways and backward from time to time. Everyone knows the ability of dipterans to instantly take off, which is nothing more than an active flight from danger. Such a rapid lifting effect is provided by the halteres. These flask-shaped rudiments of the hind wings, which act as a gyroscope when the insect moves, also perform very frequent oscillations. They provide appropriate customization nervous system and turning on the wings immediately at full frequency, which is followed by a lightning-fast takeoff.
For the vast majority of mosquitoes and flies of temperate latitudes, the spring and summer months are the period of adult activity. But there are species and even entire families that are active in the cold season. These are some greenfinches (Dolichopodidae), flying under the forest canopy in the thaw. All Trichoceridae are found in nature until late autumn. They can be seen on the snow in the middle of winter during mild frosts, for which they received the Russian name winter mosquitoes, or pre-winter mosquitoes. Similar activity is characteristic of a number of other small families. higher flies.
During the breeding season, the behavior of individual groups of representatives of the order is characterized by significant complexity. Everyone knows the columnar clusters of insects on forest and country roads. These are swarms of mosquitoes from some families, in particular bells and blood-sucking mosquitoes. They are usually formed by males, which makes it easier for them to meet females who arrive at the sounds of a swarm. Males of many other dipterans for the same purpose gather in groups at various elevations in the area. In some species, territorial behavior is clearly expressed, with males defending portions of their territory from invasion by other males. Often such a “plot” is just a leaf of a tree or bush. Real battles for the female are also known. Males push each other with horn-like projections on the head (some tropical variegated flies) or exchange blows with their front legs, as do, for example, stilt-eye flies (Diopsidae), until one of the rivals takes flight.
The food and methods of obtaining it among imago dipterans are very diverse. But at the same time, all mosquitoes and flies are similar in one thing - regardless of the type of food, food enters the body in liquid form as a solution or suspension. In Diptera there are several main types of imaginal nutrition. This is primarily nectarophagy. Many, many species of Diptera feed on nectar and/or pollen. Close to nectarophages are also consumers of rotting plant remains (fruits, berries, vegetables) rich in microorganisms - phytosaprophages. Feeding of adult dipterans on excrement (coprophagia) or decomposing corpses (necrophagia) is a rather rare phenomenon, characteristic of only a few species. But predation, on the contrary, is widespread within the order. It is not uncommon for all members of a family to be predators. A fairly common type of nutrition is hematophagy, that is, feeding on the blood of vertebrates. Blood-sucking species are representatives of 12 families. And finally, within the order there are species that do not feed at all at the adult insect stage (phagia). Many of them do not have an oral apparatus as such (for example, gadflies). A number of small mosquitoes, whose lifespan is estimated at several days, also apparently do not feed, although they have well-developed mouthparts. The aphages include some detritites (Sciaridae), bellworts (Chironomidae), bogworts (Limoniidae), etc.
All dipteran larvae are legless, often worm-like creatures. Leglessness is often compensated by roll-like thickenings, tubercles, and hooked bristles; sometimes on the ventral side there are outgrowths resembling the pseudopods of sawfly larvae. Some larvae have a well-developed head, like the larvae of many families of mosquitoes, while in others it is partially reduced, for example, in the larvae of horseflies. In the third group, which is formed by higher flies, the larvae have a completely absent head; there is only a head segment, which is no different in color from the body segments.
Diptera, apparently, have mastered all conceivable aquatic habitats, far surpassing other insects in this regard. All types of freshwater bodies of water (from lakes and rivers to small puddles, micro-ponds in leaf axils, tree hollows and pitchers carnivorous plants), reservoirs with increased acidity And high level mineral salts or organic pollution, hot springs, accumulations of water in the basements of houses or subway tunnels, warm waters coolers nuclear power plants and the gutters of livestock farms are infested with dipteran larvae. Some dipterans (several genera from the chironomidae family of mosquitoes) have also mastered the sea coastal zone. Forest litter, soil, wood at various stages of decomposition, rotting plant and animal remains, fungi, living tissues of plants and animals, etc. - all this is also mastered by the larvae of these insects. Most live inside the substrate, less often openly.
The food connections of dipteran larvae are no less diverse. Within the main types of nutrition, there is a wide range of food specialization. The method of processing food can also be very different, depending on the structure of the oral apparatus and the characteristics of digestion. Many species of Diptera (mainly flies) have developed extraintestinal digestion.
The main types of feeding of larvae include feeding on decaying plant debris (saprophagy); Moreover, an important component of such a diet are various microorganisms and fungi, an indispensable component of the rotting substrate. Very widespread among larvae and feeding fruiting bodies and mycelium of the most various types mushrooms (mycetophagy). Eating on wood (xylophagy) occurs at different stages of its decomposition. In this case, the larvae of some groups develop in more or less dense, although partially decomposed wood, while other species are able to develop only in very loose, highly decomposed woody remains of stumps. Phytophagy, that is, feeding on living plant tissues, is most widespread among the larvae of higher flies. The larvae mastered leaves, needles, tissues of stems, roots and root crops, rich nutrients tissue of plant growth cones and tissue of developing fruits.
And, finally, another type of specialization in the nutrition of phytophages is the ability to cause the formation of galls, where the larva lives and completes its development. Coprophagy is also common among larvae - feeding on animal excrement, not only vertebrates, but also invertebrates. True, feeding on invertebrate excrement, and, consequently, living in their communities has been poorly studied. There is much more information about the connections between larvae and the droppings of birds and mammals. Feeding on the corpses of vertebrate and invertebrate animals (necrophagy) is a common phenomenon for a number of larvae. In a large group of dipterans, the main type of feeding of larvae is predation. Another type of feeding for carnivorous larvae is parasitism. Some of them parasitize invertebrate animals, others are associated with vertebrates, including humans.
BI-WINGERS(Diptera), an order of insects characterized by the presence of one pair of wings. This is one of the largest and most widespread groups of insects, including approx. 100,000 species. It includes such well-known species as houseflies, mosquitoes, midges, midges, horseflies and gadflies.
Flight behavior. Although large swarms of Diptera are often observed, they are not social insects such as termites, bees and ants. On the contrary, most of them live alone, at least for most of their lives. However, many dipterans gather in a kind of swarms, attracted by the smell of food, a convenient place for resting or mating.
Clusters. Diptera can fly to the light together with insects of other species. Mosquitoes, bells and centipedes swarm closer to dusk, usually over bushes, paths or other landmarks, near which the swarm, if frightened off, gathers again. Such groups consist mainly of males; It is believed that the sound of their wings attracts females with their characteristic tone. In experiments, by producing sounds similar to the squeaking of female mosquitoes of certain species, it was possible to induce swarming of the corresponding males. Clusters are especially characteristic of blood-sucking dipterans (gnus). If a species is active mainly in the dark, it is called nocturnal, if in the light it is called diurnal; An intermediate crepuscular group is also distinguished.
« Hanging» flight observed in different species of Diptera, but especially developed in hoverflies and buzzers. Representatives of these families fly quickly and maneuver well in the air. You can often observe how they hover motionlessly in place, intensively working their wings, and then suddenly disappear from view.
General characteristics. In the vast order of Diptera there is a huge variety of body sizes, shapes and colors. The length of some gall midges is only 0.4 mm with a wingspan of just over 1 mm. Australian blackbirds reach a length of 50 mm, and the wingspan of individual tropical centipedes exceeds 100 mm.
However, despite the large number of species and diversity of dipterans, they all share common characteristics. Typically, adults have only one pair of membranous wings, rather thin integuments, 5-segmented tarsi, a licking or sucking mouthpart (proboscis) and well-developed compound (compounded) eyes. Development occurs with complete transformation (metamorphosis), i.e. a larva hatches from the egg, which, after several molts, turns into a motionless pupa, and from the pupa an adult insect (imago) is born. Diptera larvae, unlike caterpillars, are always legless.
The general structure of dipterans is the same as that of other insects. The body of the imago consists of three main parts. The head bears the mouthparts, eyes and antennae. The chest includes three segments with three pairs of walking legs and a pair of wings (their second pair, the posterior one, has turned into halteres). Almost all the space inside the chest is occupied by powerful muscles necessary to activate the locomotor organs. The abdomen consists of a varying number of externally defined segments (depending on the species) and houses the reproductive organs and most of the digestive system.
| EXTERIOR STRUCTURE OF A HOUSE FLY |
Head. Oral apparatus. Although dipteran adults use a wide range of food sources, their oral apparatus is essentially always a sucking or licking proboscis, sometimes so hard and sharp that they are capable of piercing the skin of many vertebrates or the integument of other insects. Many dipterans, including the housefly, can often be seen with their soft proboscis extended and attached to various wet surfaces. In contact with the substrate are two extended lobes of the lower lip, or oral discs, adapted for the absorption of liquid food. Numerous thin channels (pseudotrachea) on their underside converge at the central point of the proboscis, from where liquid is drawn into the head using a bellows-like pharyngeal pump.
Horseflies not only possess licking structures, but also two pairs of hard, dagger-shaped appendages—modified upper and lower jaws—for piercing the skin of the animals whose blood they feed on. Even their upper lip turned into a stylet and became an integral part of the piercing oral apparatus. (However, male horse flies do not feed on blood, and their lower jaws are reduced.)
In mosquitoes, the lower lip does not take part in feeding, but serves only as a case for the needle-shaped stiletto jaws, which fold into a thin piercing proboscis. When these jaws penetrate the body of a vertebrate, it bends and remains on the surface. The upper lip of mosquitoes (and some other bloodsuckers, such as midges, midges and tsetse flies) is also part of the piercing mouthparts. A groove runs along its lower (posterior) side, covered by another part of the oral apparatus - a long tongue, or hypopharynx. It is pierced by a channel through which saliva is supplied to the victim's wound. The mosquito absorbs the blood diluted with it through a tube formed by the upper lip and hypopharynx.
Antennas
(antennae, or cubs) of dipterans are quite diverse in shape, which is widely used to classify these insects. It is believed that their oldest species had long multi-segmented antennae, like modern mosquitoes and centipedes, the antennae of which consist of two thick basal segments and a whip-like part formed by thin, more or less cylindrical segments numbering from two to 39. In the more advanced in evolutionary terms Diptera antennae are usually formed by two basal segments and a third - thickened, of various configurations. It often bears at the end or dorsal side a thin appendage formed by the fusion of many segments - glabrous or pubescent, bristly or ringed.Breast insects consists of three segments: prothorax, mesothorax and metathorax. Since the main part of the pectoral muscles is responsible for flight, the middle segment, which carries the wings, is usually noticeably larger than the other two.
Legs attached to the chest, with each segment carrying one pair of them and containing the corresponding muscles. Like other insects, the typical Diptera leg consists of five parts: coxa, trochanter, femur, tibia, and tarsus. The terminal part (tarsus) is usually formed by five segments and ends with a pair of claws. Under each claw there is a soft glandular pad. The claws help move along rough surfaces. When walking, the soft pads are compressed and secrete an adhesive secretion, allowing the dipterans to hold on even where there is nothing to cling to.
Wings. Most insects have two pairs of wings, but in dipterans one of them (the posterior one) is transformed into small club-shaped appendages, the so-called. halteres. Individuals in which they are damaged or removed partially or completely lose the ability to fly. The halteres are movably articulated with the sides of the metathorax and vibrate in the vertical plane with the same frequency as the wings, but in antiphase with them. With the help of mechanoreceptors located at their base, they give the insect the opportunity to determine and correct balance in the air.
Thin membranous wings are strengthened by cylindrical veins. Diptera have fewer of them than most other insects, and there are especially few transverse veins. Wing venation is a very important classification feature used to divide an order into lower-ranking taxa. Near the base of the wing, on its posterior (inner) edge, there may be a notch that separates a small lobe or scale from the main plate.
Abdomen primitive dipterans are elongated, almost cylindrical and consist of 10 segments, of which the two closest to the chest are very indistinctly separated from each other. In more specialized families, the number of visible abdominal segments is smaller, in particular, it has been reduced to 4 or 5 in the housefly and its closest relatives. Shortening, the abdomen becomes closer in shape to a cone or even a sphere.
Reproductive system. The only visible abdominal appendages are the copulatory organs in males and the ovipositor in females. The latter is usually tubular or saber-shaped. In males, the expanded last segment bears special grips that serve to hold the female by the ovipositor during mating. The internal genital organs, located in the abdomen, consist of gonads (testes in males and ovaries in females), accessory glands that secrete liquid secretions, and excretory ducts. The shape of the external genital appendages in Diptera varies widely. The structure of the copulatory “captures” in males serves as the main taxonomic character in determining the species of some families.
Digestive system. The abdomen contains most of the digestive system, mainly the intestines, sometimes forming blind outgrowths. The excretory organs are the Malpighian vessels - long thin tubes that open into the intestines. In the front part of the abdomen there is a goiter - a thin-walled sac connected by a narrow tube to the esophagus. The crop serves as a temporary reservoir for liquid food. Filling with air, it probably facilitates the emergence of an adult insect from the pupa shell.
Diversity. Sexual dimorphism. One of the surprising phenomena that is often found in Diptera is sexual dimorphism, i.e. significant differences in appearance between males and females of the same species. For example, as noted above, the males of many species have holoptic compound eyes, i.e. touch each other, whereas in females they are separated by a frontal stripe (dichoptic). In female mosquitoes, the antennae are sparsely pubescent, while in males they are densely covered with long hairs. Sexual dimorphism can also be expressed in size: males are usually smaller. In females of some species, the wings are absent or greatly reduced, while in males they are normally developed. In one of the families of Diptera, in females, two veins of the wing merge at its edge, and in rare males they are separated along the entire length. In another group, the legs, antennae, or other body parts of males often bear tufts of hairs with a metallic sheen that are absent in females. The legs of the males of some mosquitoes are trimmed with a wide scaly fringe; females do not have it. Differences in coloration between the sexes are common, but usually not noticeable. However, sometimes this difference is quite significant; for example, males of one American centipede are pale reddish, while females are almost black.
Mimicry and protective coloration. Many species of harmless dipterans are strikingly similar in appearance to other insects, especially bees and wasps, which humans and probably other animals try to avoid. This phenomenon is called mimicry. A typical example of this is the appearance of a number of hoverflies; they are so similar to wasps that even an entomologist will not always immediately correctly identify the insect. Other hoverflies mimic the appearance of bees. Some flies are more or less like bumblebees. This similarity is reflected in the nomenclature of dipterans: the entire family Bombyliidae (buzzers) is named in Latin after bumblebees ( Bombus); there are bee-like hoverflies, bumblebee hoverflies, hornet-shaped moths, etc.; one of the clans of ktyrs is called Bombomima (“bumblebee imitator”).
Some dipterans avoid predators with the help of protection, i.e. camouflage, coloring. The dark color of fungus gnats makes them invisible as they sit motionless in crevices under fallen trees. Other dipterans have “dismembering” coloration. For example, in liriopids, bright black and white stripes on the body are arranged in such a way that these insects, flying against a light or dark background, simply look like sets of spots that do not form a single whole.
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| FOUR STAGES OF THE LIFE CYCLE common housefly. A - The egg of a housefly is laid on the surface of a food substrate, such as a garbage heap. b- A whitish, relatively inactive larva (maggot) hatches from the egg. V- After a period of feeding and growth, accompanied by two changes of skin (molting), the larva pupates inside its skin, which hardens and turns brown, turning into the so-called. pupary. At the pupal stage, the organs of an adult insect (imago) are formed. G- An adult fly emerges from the puparium, spreads its wings and flies away. The egg, larva, puparium and young adult are shown enlarged to the same scale. |
Like other higher insects, the life cycle of dipterans is complex and includes complete metamorphosis. The eggs of most species are oblong and light-colored. They hatch into larvae that are usually elongated, roughly cylindrical, soft-bodied and legless. In most cases, the hard parts of their heads are greatly reduced; Such worm-like larvae are called maggots. The larva feeds intensively and periodically molts as it grows. The number of larval molts varies among dipterans, but usually there are two or three. This is followed by the pupal stage. In some dipterans it is formed inside the larval skin, which turns into the so-called. "puparium". Eventually the shell of the pupa ruptures, and an adult insect (imago) is born.
Life cycle of a housefly. Using the example of the housefly, we can trace the development of dipterans. To lay eggs, the female searches for accumulations of decaying organic matter, such as manure or garbage heaps. Thus, the fly instinctively leaves the clutch where the sedentary larva will be provided with a sufficient amount of food. At one time, the female can lay 120 or slightly more narrow whitish eggs of approx. 1 mm long. Huge masses of them are found in places where several females leave their clutches at the same time. At summer temperatures of 24-35° C, egg development takes approx. 8 ocloc'k. The worm-like larvae that hatch from them are approx. 2 mm begin to feed voraciously. They grow so quickly that the first moult occurs after 24-36 hours, and the second about a day later. The third stage larva feeds for another 72-96 hours and grows to a length of approx. 12 mm and then pupates.
An oblong pupa forms inside the last larval skin, which becomes the pupal case (puparium). This shell changes its dirty white color to brown and hardens. Within 4-5 days, inside the apparently inactive pupa, the larval tissues disintegrate and rearrange themselves, forming the structures of an adult insect. In the end, the imago comes out with the help of a special frontal bladder, which, under the pressure of “blood” (hemolymph) pumped into it, protrudes into the frontal part of the head. Under its pressure, the “lid” of the puparia opens, releasing the adult insect. It crawls out of the decaying debris or soil in which it pupated, spreads its initially crumpled wings and flies off to feed and mate, starting a new life cycle.
Another curious form of reproduction found in some dipterans is pedogenesis, i.e. the appearance of offspring in apparently immature individuals. Thus, in gall midges, an adult female lays only 4 or 5 eggs, from which large larvae are formed. Inside each of them, from 5 to 30 (depending on the species and individual) daughter larvae develop. They feed on the mother's body and then reproduce themselves in the same way. After several such cycles, successive larvae pupate, and a generation of adults is formed. Larvae reproduce without mating. This development of unfertilized eggs is called parthenogenesis. This phenomenon, in the absence of pedogenesis, has been found in other dipterans, for example, in some midges. Females lay unfertilized eggs, which only hatch into females. Parthenogenesis can be cyclic, constant or sporadic. Cm. REPRODUCTION.
There is, perhaps, no corner on land where dipterans do not live. This is the most widespread order of insects, although the ranges of many of its families are not fully known. Each of the large zoographic regions is characterized by its own set of taxa, but the genera and families to which they belong can be cosmopolitan, i.e. meet almost everywhere. About two dozen species of Diptera are also cosmopolitan. About half of them were unwittingly dispersed throughout the planet by humans. These species include the ubiquitous housefly, the squeak mosquito ( Culex pipiens), the gastric horse botfly and the autumn fly. Among approximately 130 families of Diptera, less than 20 are truly cosmopolitan, although the ranges of many others are not much narrower, i.e. they are distributed subcosmopolitanly.
Diptera abound in the humid tropics. The distribution of most families is limited to this natural zone, while many others reach their maximum diversity and abundance here. In temperate or cold areas, fewer species of Diptera are found per unit area, but the number of individuals is often no lower than in the tropics. In the windswept Arctic desert, on mountaintops and among dunes, where harsh climatic conditions are unsuitable for most insects, Diptera remain the most prominent representatives of this group of invertebrates. In the north of Greenland, several hundred kilometers from the North Pole, there are centipedes, carrion flies, flower flies, bell flies and fungus gnats. On the other side of the Earth, on the Antarctic islands, there are several species of midges, hoverflies, centipedes, gall midges and some other groups. In Antarctica itself, only one species of wingless mosquitoes has so far been recorded, but it is likely that other dipterans will be found there.
Diptera of mainland islands are usually close to those living on the nearest continents, but on more isolated oceanic islands they, even belonging to widespread groups, are often very peculiar. Apparently, a single, accidental arrival of some species on such islands in the distant past led in the course of evolution to the appearance of a whole set of diverse forms. This may explain, for example, the fact that almost a third of Hawaii's 246 dipteran species belong to just one family.
Having thin integuments, most dipterans are not able to effectively retain water in their bodies. They would constantly be in danger of drying out if they did not live in more or less humid conditions. Although larvae in many cases lead an aquatic lifestyle, adults are almost always terrestrial. The only exception is sea centipedes Limonia monostromia, whose entire life cycle takes place in the warm sea waters off the coast of Japan.
Larvae. The habitats of dipteran larvae are much more diverse than those of adults and include almost all types of ecological niches. Some attack aphids or nibble the leaves of mosses and other plants, i.e. live openly. However, in most cases they develop in the thickness of a moist substrate, for example inside the leaves, stems and roots of plants. Larvae of many species make tunnels in rotting wood, fungi or soil, feeding on organic debris or microscopic invertebrates.
They often live in standing and flowing bodies of water of any size, where they feed on vegetation, microorganisms or insects of other species. Most of these aquatic larvae prefer shallow places, but in some bell mosquitoes they dive to a depth of more than 300 m. If their development requires a good supply of oxygen, they attach to the stones of river rapids or mountain streams. The larvae and pupae of some dipterans prefer water with a high content of alkalis or salts, and in one Californian species they live in oil puddles. Others are found in hot springs and geysers, where the water temperature reaches 50 ° C. The larvae of one of the mosquitoes survive even in the liquid filling the pitcher leaves of insectivorous plants, where other insects drown and are digested.
Judging by fossil finds, insects existed already in the Devonian period, i.e. OK. 300 million years ago. However, until the Upper Triassic (about 160 million years ago), no remains of dipterans were found among them. The most primitive representatives of this order are similar to centipedes and are united in the extinct family Architipulidae. Many different dipterans, close to modern forms, are found in Baltic amber - the resin of coniferous trees, fossilized in the Upper Oligocene, i.e. about 35 million years ago. The Miocene shales from Florissant, Colorado, contain many fossils of centipedes, fungus gnats, and other dipterans characteristic of marshy habitats. Among them, even the tsetse fly is noted, although at present this genus is found only in Africa. The study of Baltic amber and Florissant fossils showed that by the middle of the Cenozoic era, dipterans had passed through most of their evolutionary development.
Many dipteran species are best known as disease vectors, nuisance bloodsuckers, and crop pests. Chemical methods of combating them are the most effective, but even the newest insecticides cannot be considered a panacea, since insects quickly become resistant to them.
Vectors of human diseases. Listed below are just a few of the medically important dipterans.
Housefly mechanically transports pathogens of bacterial dysentery; it is possible that it can also spread the bacteria of typhoid fever, paratyphoid fever, cholera and the polio virus.
Horseflies can transmit from an infected animal the causative agents of tularemia, as well as one of the filariasis - loiasis.
Cereal flies from the family Hippelates When feeding near the eyes, they easily introduce bacteria into them, causing acute epidemic conjunctivitis.
Blood sucking. Blood-sucking dipterans, even if they are not carriers of diseases, such as biting midges, autumn flies, many mosquitoes and midges, when attacked en masse, worsen human health, causing itching and allergic reactions, sharply reducing performance. In addition, all of these species remain potential spreaders of pathogenic agents.
Pests of agricultural plants. Compared to beetles, butterflies, herbivorous bugs and representatives of some other orders of insects, dipterans cause relatively little damage to agricultural plants. Representatives of only 5-6 families have a certain significance in this sense. The Hessian fly from the gall midge family is a serious pest of grain crops. This species mainly damages wheat, but is also dangerous for barley and rye. Hessian fly larvae feed on plant sap at the base of stems, causing stunted growth and lodging. With the development of wheat varieties resistant to this attack, the importance of this agricultural pest has decreased. The variegated fly family includes many species that feed on the succulent fruits of various plants, but only a few of them cause serious damage. Thus, the larvae of the apple moth fly spoil apples, damage the fruits of citrus and other fruit trees, significantly reducing the yield. The larvae of other dipterans gnaw tunnels in various plants. As an example, we can cite three species from the family of flower flies: sprout flies, cabbage flies and onion flies. Representatives of the family of cereal flies, living in many parts of the world, damage grain crops.
The order Diptera (Diptera) is divided, according to different systems, into 121-138 families, which are grouped into two or three suborders. When classifying, the most commonly used characters are the venation of the wings, the length of the antennae and the number of segments in them, the number and location of bristles and spines on the body and legs, the configuration of the external genital appendages, the presence or absence of simple ocelli and the shape of the hole through which the imago leaves the pupal skin or puparia. Coloration, size and body shape do not always allow us to judge the degree of relationship, because natural selection often leads to external similarity between representatives of very distant groups. The scheme proposed below, including only the most important families, is only one of the possible ways of classifying the approximately 100 thousand species of Diptera; the number of species in families is indicated approximately.
Suborder Nematocera (long mustache). These insects are characterized by long antennae with more than three segments. The group includes 36 families. The antennae of the imago consist of 6 or more approximately identical, movably connected segments, and the mandibular palps usually consist of 4 or 5. The larvae have a well-developed dark-colored head capsule. The pupa is not enclosed in a larval skin, i.e. no puparia is formed.
Tipulidae (centipedes): 10,000 species, cosmopolitan.
Psychodidae (butterflies): 400 species, subcosmopolitan.
Chironomidae (bellers, or jerks): 2000 species, cosmopolitan.
Ceratopogonidae (biting midges): 1500 species, subcosmopolitan.
Culicidae (true mosquitoes): 1600 species, cosmopolitan.
Mycetophilidae (fungus gnats): 2400 species, cosmopolitan.
Cecidomyiidae (gall midges): 4500 species, subcosmopolitan.
Bibionidae (centipedes): 500 species, mainly in Eurasia and North America.
Simuliidae (midges): 600 species, subcosmopolitan, but especially numerous in Eurasia, North and South America.
Blepharoceridae (reticulate wings): 75 species, found in highlands.
Suborder Brachycera (short-whiskered) includes approximately 100 families. The antennae of adult insects consist of three segments, of which the last (distal) is thickened and bears an appendage in the form of a seta or rod on the dorsal side or apex. Palpi of one or two segments. The head of the larva is poorly formed or rudimentary. Representatives of some families (straight-suture) have a free pupa; in other cases (round-suture dipterans) it develops inside the puparia.
Tabanidae (horseflies): 3000 species, mainly in the tropics and subtropics.
Stratiomyiidae (lion flies): 1500 species, subcosmopolitan.
Rhagionidae (snipe): 500 species, mainly in North America and Eurasia.
Nemestrinidae (long-proboscideans): 250 species, subcosmopolitan, but mainly in Central and North Africa.
Bombyliidae (buzzers): 2000 species, subcosmopolitan, but mainly in North America and the Mediterranean.
Asilidae (Ktyri): 5000 species, subcosmopolitan, but most diverse in the tropics.
Mydaidae: 200 species, distributed in many but isolated regions.
Dolichopodidae (greenfinches): 2000 species, cosmopolitan.
Empididae (pushers): 3000 species, mainly in Eurasia, North and South America.
Phoridae (humpbacks): 1000 species, mainly in the tropics.
Platypezidae (fungus flies): 100 species, mainly in Eurasia and North America.
Pipunculidae: 400 species, mainly on the northern continents.
Syrphidae (hoverflies): 4000 species, subcosmopolitan.
Conopidae (bigheads): 500 species, subcosmopolitan.
Ortalidae (spot wings): 1200 species, cosmopolitan, but especially abundant in the tropics.
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AVERAGE LENGTH OF BI-WINGERS, MM |
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| Buzzed | |
| Bighead | |
| Midge | |
| Lacewing | |
| Hessian fly | |
| Gadfly gastric | |
| Bullfly | |
| Sheep fleece | |
| Mosquito | |
| Spotwing | |
| Ktyr | |
| Gadfly subcutaneous | |
| Hoverfly | |
| Ezhemukha | |
| American Meromisa | |
Trypetidae (pied wings): 2000 species, mainly in the tropics and subtropics.
Sciomyzidae (tentails): 200 species, mainly in the northern continents and southeast Asia.
Drosophilidae (fruit flies): 750 species, subcosmopolitan.
Ephydridae (shorebirds): 800 species, mainly in Eurasia and North America.
Chloropidae (cereal flies): 1200 species, cosmopolitan.
Agromyzidae (mining flies): 1000 species, cosmopolitan, but especially abundant in Eurasia.
Anthomyiidae (flower girls): 3000 species, cosmopolitan.
Calliphoridae (carrion flies): 500 species, subcosmopolitan, but mainly in the Northern Hemisphere.
Sarcophagidae (gray blowflies): 1000 species, subcosmopolitan but mainly in the tropics.
Muscidae (true flies): 150 species, cosmopolitan.
Tachinidae (jermules): 5,000 species, cosmopolitan but most diverse in the tropics.
Oestridae (nasopharyngeal botflies): 150 species, subcosmopolitan, but mainly in warm areas.
Diptera are one of the largest orders of insects, numbering more than 100 thousand species. These insects have one pair of wings (the hind wings are modified into club-shaped halteres - halterae).
The oral apparatus has the form of a proboscis, adapted for sucking liquid food from plant and animal tissues or for licking it. Diptera are insects with complete metamorphosis.
The order includes three suborders (Fig. 52). The suborder of long-whiskered dipterans Nematocera unites species with multi-segmented antennae (Fig. 52, A). Their larvae have a well-developed head. The pupae are covered type and are often able to move by contracting the abdominal muscles.
The suborder Brachycera-Orthorrhapha is a group of species whose antennae, as a rule, have three segments (Fig. 52, B). The head capsule of the larvae is reduced. Covered type pupa. When the imago emerges from the pupal exuvium, a straight suture is formed on its dorsal side.
The suborder of short-sutured dipterans Brachycera-Cyclorrhapha includes species in which the antennae are three-segmented (Fig. 52, B), and the larva has no head capsule. During the process of pupation, the exuvium of the last larva is not shed, but becomes denser, darkens, turning into a false cocoon - puparia. Inside the puparia there is a free-type pupa. When the imago emerges from the puparium, a round cap is formed (opening occurs along a rounded seam on the anterior wall of the puparium).
Rice. 52. Body structure of short-whiskered dipterans: A - mosquito of the genus Aedes, B - horsefly Tabanidae, C - true fly Muscidae (according to Violovich, 1968, from Narchuk, 2003).
The body of dipterans is divided into the head, thorax and abdomen (Fig. 52) and is covered with bristles and hairs. The head is flattened at the back,
hemispherical. On the sides of the head there is a pair of compound eyes. Between the eyes on top is the forehead (Fig. 53). The upper part of the forehead is called the crown. The part of the Diptera's head located below the antennae is called the face. The antennas are located on the border of the forehead (it is located on top) and the face (it is located below). The sides of the head below the eyes are called the cheeks. The setae covering the head are divided into frontal (limit the sides of the frontal stripe), orbital (located lateral to the forehead), ocellar (between the ocelli), parietal, vibrissae (at the edges of the mouth) and others (Fig. 53).
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Rice. 53. Head of a fly: ar - ar ista, g - ocelli, t - crown, mustache - antenna, Zchl - third antennal segment, sp - zygomatic plates, tp - parietal plates, l - lunula, lp - middle frontal stripe, sch - cheek, m - median, lsh - facial suture, op - orbits, fc - frontoclypeus (face).
In most cases, in male dipterans the eyes touch on the forehead, while in females the eyes are separated by a stripe of the forehead. According to this characteristic, the eyes of males are called holoptic, and the eyes of females are called dichoptic.
There are three simple ocelli on the crown. In addition to a pair of compound eyes, oral apparatus and simple ocelli (usually of 3), there is a pair of antennae (antennae) on the head. In Diptera appearance antennae are varied. In general, the antenna consists of a main segment (scape), a second segment (pedicel) and a flagellum (flagellum). The number of flagellum segments may vary. The scape is reduced to one degree or another (especially in higher Diptera). The pedicel is well developed in many long-horned dipterans and contains Johnston's organ (a sensory organ that perceives the movement of the flagellum). In Nematocera, the flagellum initially has 14 segments, in primitive Brachycera - 8 segments (in representatives of Asilomorpha - 3 segments), in Cyclorrhapha - 4 segments. In higher short-haired dipterans, the first segment of the flagellum is enlarged and is called the first flagellomere (third segment of the antenna), the remaining segments are greatly reduced and form a stylus (rod-shaped appendage) or arista (thread-like appendage). The stylus may contain 1 or 2 segments, the arista consists of 3 segments (in some syrphids and empidids there are 2 segments). The structure of the arista and stylus may be different (Fig. 54, 55). The back of the head (postcranium) carries into the foramen magnum. The part of the head above this opening is called the occiput, and the area of the head below the opening is called the buccal part.
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Rice. 54. Sciomyzidae: head and its parts: A - frontal view of the head of Sepedon (antennae), B - right half of the head of Pteromicra, C - arista Coremacera; Conopidae: G -. Zodion (head from front) (original)
The thorax contains three segments, like those of other insects. In dipterans, the mesothorax reaches its greatest development (one pair of wings is attached to it). The prothorax from above (pronotum) is divided into anterior and posterior parts. The anterior part - the pronotum - is most developed in Nematocera, and rear end- postpronotum - in higher Diptera. The dorsal surface of the mesothorax (mesonotum) is divided into prescutum, scutum, scutellum (scutellum) and postnotum (with postscutellum).
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Rice. 55. Head section and its parts Conopidae (A - Physocephala) and Tachinidae (B - Ectophasia, C - Heliozeta, D - Cylindromyia); sensorium of the antennae of Thecophora (Conopidae): D - surface of the second antennal segment, E - surface of the third antennal segment.
The mesonotum (dorsal surface of the mesothorax) is divided
a transverse suture, and the posterior section of the mesonotum (scutellum) is separated by a transverse groove. There are spiracles on the sides of the chest. Dorsal surface and side surfaces the breasts are covered with a variety of setae: acrostichal, dorsocentral, intraalar, occlusive, humeral and notopleural, hypopleural. The legs end in a five-segmented tarsus with a pair of claws and two pulvillas. The wings are located on the mesothorax; they are membranous, transparent (sometimes with a dark pattern), with longitudinal and transverse veins limiting the corresponding cells. The metathorax in Diptera is reduced. A pair of halteres is located on the metathorax.
Representatives of a number of families of round sutures have developed scales - calyptra (these families are included in the group Calyptratae); others do not have it (Acalyptratae). The wing structure of Diptera is also used in identifying species.
For convenience, the wing is divided into an axillary region containing axillary plates between the lateral edges of the notum and the base of the veins, a basal trunk containing the bases of the veins and membranes, and a lobe - the main region of the wing. The axillary region (Fig. 56) consists of several elements.
The leading edge of the wing is called the costal margin. The most proximal part, lying at the base of the wing, is called the tegula (costal plate). The more distal part adjacent to the tegula is called the basicosta (shoulder plate). It is in contact with the costal vein (C). Three more axillary plates are associated with
basicosta: first, second and third. First axillary plate
its process comes into contact with the subcostal sclerite. Proximally, the second axillary plate is adjacent to the first axillary plate, anteriorly to the base of the radial vein (R), and posteriorly to the third axillary plate. The third axillary plate is adjacent to the posterior alar process, the base of the cubital vein (C) and the anal vein (A), as well as the second axillary plate. Sometimes there is a fourth axillary plate lying near the third axillary plate.
In the median region of the wing, distal to the second and third axillary plates, there are proximal and distal median plates. These are parts of the third axillary plate, separated from the base of the medial (M) and cubital (C) veins. This part is separated from the distal median plate by a basal fold. The posterior - basal part of the axillary membrane, connecting the posterior edge of the wing with the chest, forms two basal lobes - calyptera (scales). The proximal lobe - the lower wing scale (lower calypter) - begins in the form of a narrow ligament and ends near the distal lobe - the upper wing scale (upper calypter). There is a clear notch between the calypters.
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1989: Manual of Nearctic Diptera): A1, A2 - branches of the anal veins, C - costa (costal vein), C - cubital vein, CuA1, CuA2 - anterior branches of the cubitus, CuP - posterior branch of the cubitus, M - medial vein, M1, M2, M3 - posterior branches of the medial vein, MA - anterior branch of the medial vein, R - radial vein (radius), R1 - anterior branch of the radius, R2, R3, R4, R5 - posterior branches of the radius, Rs - radial sector, Sc - subcosta (subcostal vein), a1, a2 - anal cells, bc - basal costal cell, bm - basal medial cell, br - basal radial cell, c - costal cell, cua1 - anterior cubital cell (cubital fork), cup - posterior cubital cell , d (lm2) - discal cell, dm - discal medial cell, m1, m2, m3 - medial cells, r1, r2, r3, r4, r5 - radial cells, sc - subcostal cell; crossveins: bm-cu - basal medial-cubital, dm-cu - discal medial-cubital, h - brachial, m-cu - medial-cubital, m-m - medial, r-m - radial - medial, sc-r - subcostal - radial .
The wing trunk contains the bases of all the main veins, the bases of their plates and struts. The subcostal sclerite connects the subcostal vein with the first axillary plate and is wedged between the basicosta and the edge of the base of the radius (radial vein-R). The main section of the radius is called the stem vein. Apically it is connected with the transverse humeral vein (h). The posterior edge of the stem vein usually has a wide lobe - alulu (axillary lobe). It is separated from the rest of the wing by an alular notch (alular incision).
The main part of the wing (blade) in long-whiskered and a number of short-whiskered straight-sutured dipterans is clearly visible by the thickened pigmented pterostigma.
The venation of the wings is very diverse within the order and is of great taxonomic importance.
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Rice. 57. Structure of a mosquito wing: 1 - cross vein, 2 - costal vein (C), 3 - costal cell, 4 - subcostal vein (Sc), 5 - subcostal cell, 6 - radial vein R1, 7 - radial vein R2, 8 - radial vein R3, 9 - radial vein R4+5, 10 - medial vein M1+2, 11 - medial vein M3, 12 - cubital vein Cu1, 13 - cubital vein Cu2, 14 - anal vein A, 15 - axillary cell, 16 - anal cell, 17 - first marginal (marginal) cell (Mattingly, 1952).
58. Wings of long-whiskered (A-D) and short-whiskered straight-seated (D-E) dipterans: A - Culex pipiens (Culicidae) (Hendel, 1950), B - Simulium spp. (Simuliidae) (Rubtsov, 1954), B - Culicoides nubeculosus (from Bei-Bienko, 1970), D - Culicoides circumscriptus (Ceratopogonidae) (Bei-Bienko, 1970), D - Chrysops pictus (Tabanidae) (Olsufiev, 1969), E - Bombylius major (Bombyliidae) (according to Paramonov and Zaitsev from Bei-Bienko, 1970)
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Rice. 59. General structure wing of Paralucilia wheeleri (Wood, McAlpine, 1989: Manual of Nearctic Diptera): 1 - stem vein, 2 - costal gap, 3 - humeral gap, 4 - subcostal gap, 5 - alular notch. The rest of the designations are the same as in Fig. 56.
On the wing surface there are costal (costa - C), subcostal (subcosta - Sc), radial (radius - R), medial (media - M), cubital (cubitus - C), anal (A) veins. In general, each of these veins consists of two main branches: a convex anterior branch (A) and a concave posterior branch (P). In primitive cases, both main branches branch in turn. In Diptera, the anterior branch of the radius R (RA) is designated as R1, and the remnants of the four posterior branches of the posterior branch R (RP) or radial sector (Rs) are designated as R2, R3, R4 and R5. The anterior branch of the medial vein MA is greatly reduced and never reaches the edge of the wing, and parts of the internal branch of the MP are designated as M1, M2, M3. At the same time, for Cu both branches (A and P) are designated as follows: CuA, CuP. Accordingly, the branches of the anterior cubitus are designated as CuA1, CuA2. For the anal vein, the anterior branch is designated A1, and the posterior branch is designated A2 (Fig. 56).
Cross veins may be developed: humeral (h), subcostal - radial (sc-r), radial - medial (r-m), medial-cubital (m-cu or bm-cu), medial (m-m), sectoral (r-s). The veins form and close the cells: basal costal (bc), costal (c), basal radial (br), basal medial (bm) and discal (d).
The costal vein in different groups of Diptera can give from one to three interruptions.
The venation of the wings undergoes significant evolutionary transformations associated with the reduction of veins and their branches, the appearance various combinations veins, etc., and therefore has important diagnostic value. Most full set Many long-whiskered Diptera have veins (Fig. 57, 58). In short-whiskered birds the wing structure is different (Fig. 59).
The abdomen of Diptera initially contains 11 segments (rudiments from the 11th segment are preserved: the cerci and anus). The posterior (apical) part of the abdomen undergoes transformations associated with the development of a complex reproductive apparatus in males and an ovipositor in females. In higher dipterans, the number of abdominal segments is reduced to 4.
In development, dipterans pass through the stages of egg, larva, pupa and imago.
In the process of mastering terrestrial conditions, not only insect imagoes, but also pre-imaginal stages of development have developed various adaptations. The shells of insect eggs, in addition to their protective function, provide respiration, reduce the level of evaporation and have other features that allow the embryo to survive in the external environment.
The insect egg is protected by two shells of different origins. One of them - the yolk membrane - is the primary membrane formed by the egg itself. The other - the outer membrane - is formed by the follicular epithelium of the ovary and is called the chorion. It often has a peculiar architecture, differing among representatives of different families, genera and sometimes species. The egg is usually oval in shape, with a slightly narrowed anterior pole. In some insects, the egg can be round, round-oval, teardrop-shaped, cylindrical, spindle-shaped. In the egg, one can distinguish the anterior and posterior poles, the lower (ventral) and upper (dorsal) surfaces. Sometimes the surface structure of the upper and lower parts of the egg is morphologically and functionally different.
At the anterior pole of the egg there may be well-defined structures associated with the micropyle (serves for the penetration of sperm into the egg) and the aeropilar zone (contains respiratory crypts) (Fig. 60). Much less common cases have been observed where the aeropilar region is located on the posterior or both poles of the egg. In a significant number of insect species, the egg has appendages in the form of protrusions, collars, horns, and processes. Often the appendages perform a respiratory function, less often they
provide buoyancy of eggs, or facilitate the attachment of eggs to a specific substrate, or act as springs and increase the elasticity of the chorion. Apparently, in some cases the processes
multifunctional, since in addition to the main one, they also have secondary functions.
The chorion (especially its upper part) is often thickened and is a strong formation that protects the embryo from
mechanical damage, deformation, in some cases reducing friction. Of particular importance for the embryo is the development of various types of respiratory systems of the chorion.
The eggs of a number of insects exhibit plastron respiration. A plastron is a gas film of constant volume and widespread water-air interaction. Such films are held together by hydrophobic networks of various types and are resistant to wetting under hydrostatic pressure, to which they are normally exposed in nature. In well-aerated water, the plastron allows oxygen to be extracted from the surrounding water. Plastron respiration is widespread among terrestrial eggs.
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Diptera insects, especially round-suture insects, are characterized by extraordinary variety development conditions and types of nutrition of larvae.
Diptera larvae are very diverse. The head section may have a well-defined head capsule with oral organs,
adapted for biting and chewing food, and can be significantly reduced, partially or completely immersed in the thoracic region and have oral organs adapted for penetration, rubbing or scraping. In some cases, the head section may be completely absent. Segments of the larval body tend to merge or subdivide and may bear filaments, appendages and processes. There are no legs.
The larvae of most Nematocera have a well-defined horizontal head capsule with jaws that usually bear teeth (eucephalic larvae). The larvae of straight-sutured dipterans experience varying degrees of reduction of the head capsule, which in many is immersed in the thoracic region of the body; the jaws are usually sickle-shaped and located in a vertical plane (hemicephalic larvae). Further reduction of the head capsule is accompanied by the development of the internal oropharyngeal apparatus, which is characteristic of round-sutured dipterans (acephalic larvae).
An order of insects with complete metamorphosis. The most highly organized order, the representatives of which have one (front) pair of membranous transparent or colored wings. The hind wings are vestigial and transformed into halteres. Mouth parts piercing or licking. According to the structure of the moths, they are divided into two suborders: the long-whiskered (Nematocera), which includes mosquitoes, midges, midges, long-legged mosquitoes, bells, or bloodworms, gall midges, etc., and the short-whiskered (Brachycera), which includes horseflies, flies, gadflies, tachines , ktyry, bloodsucker and many others. The transformation is complete. The larvae are legless and often (in flies) without a separate head. Pupae are free or barrel-shaped.
Diptera, as well as Hymenoptera, play an important role in nature and human economic activity. The negative value of Diptera is great. A number of forms harm plants, including agricultural crops.
Botflies cause great damage to livestock production.
A serious pest is the Wohlfahrtia magnified fly, which lays larvae - it is viviparous - in the nose, ears, anus of mammals, as well as on wound and ulcerative surfaces. The larva feeds on living tissue, then emerges and pupates in the ground. There are known cases of human infection with Wohlfarth fly larvae. Flies lay larvae mainly on people who sleep during the day under open air. The larvae live in a person's ears, nose, frontal sinuses, gums, eyes and cause severe suffering.
Of great medical and veterinary importance are blood-sucking forms that carry pathogens of a number of dangerous diseases: mosquitoes of the genus Anopheles - malaria, mosquitoes (Phlebotomus) - leishmaniasis, horseflies (Tabanus) - tularemia, some animal trypanosomas, anthrax, tsetse fly (Glossina morsitans) - sleeping sickness, etc.
The positive significance of dipterans is also very significant, many of which are important pollinators of flowering plants. Predatory (ktyri) and parasitic (tachyna) destroy harmful insects. The larvae of bell mosquitoes, or bloodworms (family Chironomidae), serve as food for many fish and waterfowl. Adult dipterans, often found in huge numbers, are an important component in the diet of entomophages - insectivorous birds, bats, etc. The order contains about 80,000 species.
