Giant dragonflies. Coursework: Evolution and origin of insects

Then let's find someone else - a giant.

Giant Dragonfly, Southeast Petaltel (lat. Petalura gigantea) is one of the largest dragonflies. It lives exclusively in Australia: along the east coast of New South Wales.

So, in general, you probably can’t tell from the photograph that she is a giant. Or will those who constantly encounter dragonflies say this?

Females are much larger than males:

Giant dragonflies are of great value to collectors from all over the world, which leads to an annual decline in the population of these unusual insects. In 1998, this species of dragonfly was declared endangered and listed in the Red Book.

Here's what's interesting:

320 million years ago there were no fishermen, no birds, no pterodactyls. While four-legged amphibians and reptiles were still timidly huddling around reservoirs, dragonflies - the first of the living world - made their way into the air. They did not fly very skillfully, but they were of a respectable size.

If the largest of modern dragonflies - Megaloprepus caerulenta from South America - has a wingspan of 19 cm, then in the ancient dragonfly Meganeura it reached, according to some sources, 75 cm, according to others - a little less than a meter. This largest known insect was already a dangerous and voracious predator with virtually no competitors. Meganeura's prey was not much inferior to it in size - herbivorous and slow-moving dictyonevrids reached the size of a pigeon and after some time were exterminated by dragonflies as a species.

Why did dragonflies (and other insects) shred so much in the future? It's worth starting with the fact that 300 million years ago the oxygen content in the air was not 21%, as it is now, but 35%. Lushly growing mosses, horsetails and ferns actively saturated the atmosphere with oxygen, and there was no one to consume it. Even the fungi and bacteria responsible for decomposition did not form, so oxygen was not consumed for oxidation processes. As a result, the dead plants did not rot, but turned to stone, subsequently forming deposits of the well-known coal (which is why this entire period will be called Carboniferous).

Why are there no giant dragonflies on Earth now? Why do the descendants of six-legged giants now not exceed the size of a chicken egg (which is reached by the well-known Goliath bronze beetles, South American stag beetles and Far Eastern longhorned beetles)? To answer this question, you should think about what prevents insects from growing unlimitedly in all directions.

Contrary to popular belief, this is not a hard shell of chitin at all: all insects that have it grow immediately after molting, when the old “corset” has already been shed, and the new clothes are still soft and stretchable. The limitation that prevents them from constantly increasing in size is the respiratory system of these amazing creatures. Let me remind you that the “blood” of insects - hemolymph - is devoid of respiratory pigments (like our bright red hemoglobin) and does not participate at all in the transfer of oxygen.

Therefore, their breathing is carried out using tracheas - branching tubes that open on the sides of the back of the abdomen and directly connect the cells of the internal organs with the air environment. Moreover, the tracheal network in insects is so dense and branched that it literally covers every cell of the body.

However, until now, scientists were not entirely clear why not all representatives of the Carboniferous insect fauna were giants. Coal cockroaches, for example, were not much larger in size than their modern descendants. To solve this mystery, a group of American scientists from the University of Arizona (Temple, USA), led by John Van den Broeks, conducted one interesting experiment. They decided to grow dragonflies and cockroaches in conditions of hyperoxia, that is, high oxygen levels, and see what prevents the latter from becoming giants in such conditions.

During the experiment, dragonflies in an atmosphere containing 35% oxygen developed in the same way as their carbon ancestors - they grew quickly and at the same time increased in size (the wingspan of these “oxygen giants” reached 50 cm, which is only 20 cm less that of Meganeura). But the cockroaches demonstrated a completely different “behavior” - they grew slowly, much more slowly than under normal conditions, and never turned into giants.

It turns out that the very fact of a large amount of oxygen in the atmosphere did not at all force all insects to become “six-legged titans.” Only those who needed it became them - mostly active predators. Those who ate the remains of animal corpses and parts of plants preferred to increase the amount of storage tissue - if you are not very active, then an extra supply of body weight will not hurt. Or, perhaps, the cockroaches were simply afraid to increase greatly in size - what if Meganeura noticed, and then... In general, nothing good will clearly happen.

Like any Golden Age, the era of giant insects has ended. This happened about 290 million years ago, when the amount of oxygen on Earth began to decline. By that time, “factories for processing wood” from microorganisms and fungi had already appeared on land, so there was no longer any excess O2 - everything that plants created went into their own processing, as well as into the respiration of all land creatures (which in the end carbon has become many times more).

Since then, insects have never grown to the size of “six-legged titans.” Perhaps this is for the best - it’s unlikely that any of us would like a mosquito the size of a kitten flying into the window. Or a fly of the same length.

source
http://unnatural.ru
http://vzglyadzagran.ru

It is believed that ancient insects were huge because there was more oxygen in the earth's atmosphere then. This is partly true.

But another important reason for their gigantism is the lack of competition among vertebrates. Millions of years ago, long before the first dinosaurs appeared, arthropods were the main predators on the planet.

Giant sea scorpion

This creature existed between 460 and 255 million years ago. Only recently scientists managed to find its fossilized claw, which made it possible to imagine what size this monster actually reached. It turned out that it was almost half a meter larger than previously thought. This sea scorpion was about 2 meters long.

Meganeura

Meganervas are a separate species of dragonfly-like insects that lived during the Carboniferous period approximately 303-298 million years ago. Today they are considered the largest insects that have ever existed on Earth. The wingspan of these dragonflies could reach 75 cm. They were predators and hunted other insects - dictyonevrids, which were the size of an average pigeon.

Giant fleas

Yes, the Jurassic period also had its own giant fleas. They lived on dinosaurs and pterosaurs and ate them. Well, as usual, they were much larger in size than their modern counterparts. One such flea from the Jurassic period could reach 2.3 cm. This, of course, is not as impressive as a two-meter sea scorpion. But nonetheless.

Pulmonoscorpion

On land there was also a species of giant scorpions. In the period from 336 to 326 million years ago, such giants up to 70 cm long crawled across the Earth.

Anomalocaris

This arthropod is one of the largest organisms of the Cambrian period. It is believed that the body length of Anomalocaris could reach 60 cm. Moreover, it also had the most developed eyes among all species of that period. Excellent vision was provided to him by 16 thousand hexagonal lenses in two compound eyes. For comparison, a modern fly has about 4 thousand lenses in its eyes.

Hallucigenia

A very strange creature. This is partly why it is called that, because it looks like a hallucination. Most likely, Hallucigenia were the ancestors of modern tardigrades and arthropods. Outwardly they look like a worm with two rows of stilted legs and dorsal spines. They had an elongated head with simple eyes. And the length of the body reached only 3 cm.

Arthropleura

An unrealistically huge two-legged centipede. These monsters lived on Earth from the late Carboniferous to the early Permian period, approximately from 314 to 290 million years ago. These are the largest known land invertebrates. Arthropleura had 30 pairs of legs and a flat body up to 2.6 meters long. Until now, however, it remains a mystery what these centipedes ate. Scientists still cannot solve this question, because none of the fossils found has a mouth preserved.

Modern insects cannot boast of large sizes, and the word “insect” itself and its derivatives are synonyms for something small and defenseless. But this was not always the case, because in past geological eras our planet was inhabited by such huge insects that it is even difficult to imagine them.

Meganeuras are the largest insects that have ever lived on our planet. Outwardly, they were very similar to modern dragonflies with a wingspan of up to 65-100 centimeters. Giant insects from the genus Meganeura reached their peak about 300 million years ago during the Carboniferous period, although they appeared on the planet at the beginning of the Paleozoic. The Carboniferous is generally characterized by the presence of a large number of large insects that flourished in a warm and humid climate. In that distant era, amphibians and large insects reigned on Earth, and primitive reptiles, the ancestors of giant dinosaurs, had just emerged as a separate class of animals.

The first fossil remains of Meganeura were found in France in 1880. According to paleontologists, meganeuras, both adults and their larvae, were predators and fed on other smaller insects. But why did giant dragonflies and millipedes flourish during the Carboniferous period, and in subsequent eras their extinction and the appearance of related species, but more modest in size, were noted?

Scientists were able to find out that the body size of insects that breathe using tracheas is related to the level of oxygen in the atmosphere. During the Carboniferous period, conditions arose on the planet that resulted in the formation of a large number of coal deposits formed from plant remains. These huge volumes of biomass were derived from decomposition processes that, accordingly, did not require oxygen in the atmospheric air. As a result of lower oxidation costs, the atmosphere experienced higher oxygen levels than in previous periods.

This feature, according to a number of experts, could be the reason that the Carboniferous was inhabited by very large insects that used tracheas for breathing, including meganeuras. Then another period with a high oxygen content was observed on Earth; by that time, birds had already appeared in the air, which did not allow flying insects to develop to such gigantic sizes.

Despite the fact that modern insects have greatly decreased in size, and the largest of them can easily fit in the palm of your hand, representatives of this class can still be called the most prosperous on the planet. Today, science knows more than 1 million species of insects, but, according to experts, there are much more of them - from 2 to 6 million, and entomologists are simply not able to describe and study them all.

These amazing dragonflies

These amazing Odonata dragonflies

There are about 6,500 species in the order Odonata, grouped into over 600 genera. Adult dragonflies are medium to large, brightly colored, diurnal insects that hunt in the air for prey they spot with their huge eyes. They are found near fresh water sources, although some dragonfly species may occur in a wide range, away from their breeding areas. Dragonfly larvae are an aquatic predator that is found in all types of inland waters.

Ancient dragonflies

During the Cretaceous period there lived giant dragonflies, with a wingspan of about 0.7 m.

Huge eyes

The dragonfly has a large head and a mobile neck. When examining a dragonfly, attention is drawn to its huge eyes, which occupy most of the head and are divided in the middle. The eye consists of 28 thousand facets (ommatids), each of which is served by 6 light-sensitive cells. For comparison: the number of facets in the eye of a fly is 4 thousand, that of a butterfly is 17 thousand. Facets located in different areas of the eye have a different structure, which determines the ability to perceive objects of different degrees of illumination and different colors. There are dark spots that block the areas responsible for vision. The image appears in the lobe of the brain that lies just below the surface of the eye. The “cilia” on the eye can be compared to antennas; their function is to detect a light source and orientate themselves during flight. The ability of the antennas is so high that the dragonfly never loses the light source during flight, which allows its movement to be precisely targeted (and as is known, the speed of the dragonfly is one of the highest in the insect world).

Balance

The thin rod-shaped abdomen acts as a balancer during flight.

Record for speed among insects
Dragonflies are the fastest flying insects. The usual flight speed of a dragonfly is 30 km/h. But their maximum speed reaches 57 km/h.

Why do dragonflies need tongs on their abdomen?

Males have “tongs” at the top of their abdomen, with which they hold the female by the neck during mating. Such “tandems” of dragonflies can often be observed near water bodies. Female dragonflies drop their eggs into the water or place them in the tissues of aquatic plants using a piercing ovipositor. The legs of a dragonfly are weak; they are capable of holding an insect on a blade of grass or holding prey, but are not suitable for walking. The dragonfly's abdomen is long; in rare species it is shorter than the length of the wings and very flexible. Both sexes can have 10 segments. In males of the genus Zygoptera there are secondary genitalia (genital appendages) on the 2-3 segments below, in females there is an ovipositor opening on the 9-10 segments.

Which there are wings

Large wings with reticulate venation in large dragonflies are always spread out to the sides, in small ones (arrows, lute) they can fold along the body at rest. Some dragonflies have wings of the same shape, narrowed towards the base (suborder Homoptera), while others have hind wings wider than the front ones, especially at the base (suborder Hemoptera). The color of dragonflies is dominated by blue, green, and yellow tones; a bright metallic sheen is less common. Some have spotted or darkened wings. In dried specimens, the color fades greatly and changes.

Two hearts

At the initial stage of development, the dragonfly larva has 2 hearts: one in the head and the second in the back of the body. A more mature dragonfly larva has 5 eyes, 18 ears, and an 8-chambered heart. Her blood is green.

Hindgut: organ of movement and respiration

The hindgut of the dragonfly larva, in addition to its main function, also serves as an organ of movement. Water fills the hind intestine, then it is thrown out with force, and the larva moves according to the principle of jet motion by 6-8 cm. The nymphs also use the hind intestine for breathing, which, like a pump, constantly pumps oxygen-rich water through the anus.

The largest dragonfly

Fossil remains of dragonflies date back to the Jurassic period. They cannot be classified into any of the currently existing three suborders, so they are classified in the fossil orders: Protozygoptera, Archizygoptera, Protanisoptera and Triadophlebiomorpha. The separate order Protodonata, sometimes placed as a suborder within the order Odonata, contains many large dragonflies, including some impossibly large dragonflies. The largest of the giant dragonflies, Meganeuropsis permiana, has a wingspan of 720 mm.

For modern species this figure is smaller; large species have a wingspan of less than 20 mm (species Nannodiplax rubra, family Libellulidae) or more than 160 mm (species Petalura ingentissima, family Petaluridae): some modern dragonflies of the genus Zygoptera have a wingspan of 18 mm (species, Agriocnemis pygmaea, family Coenagrionidae) up to 190 mm (species Megaloprepus caerulatus, family Pseudostigmatidae). The largest modern dragonfly is recognized Megaloprepus caeruleata, living in Central and South America, it has a body length of 120 mm and a wingspan of 191 mm. A rare giant Australian dragonfly with a wingspan of 110 - 115 mm (females up to 125 cm). And although the giants of the insect world live in the tropics, rocker dragonflies, found in our country, are considered one of the largest insects.

Rocker arms

The largest dragonflies in our country belong to the rockers (Aeschnidae). One of the common types is blue rocker (Aeschna juncea), body length up to 70 mm, and wingspan up to 95 mm. Males are brighter, with a predominance of blue coloring, especially on the abdomen. In females, green and yellowish tones predominate. These are excellent flyers, capable of traveling tens and even hundreds of kilometers, settling in new bodies of water. Sometimes it is possible to observe the process of a dragonfly emerging from a larva, which for this purpose climbs out of the water onto protruding parts of plants. The wings of a young dragonfly are still fragile, cloudy, and the covers are pale colored. But within an hour after hatching, the dragonfly is ready to fly.

Grandmas

The family of dragonflies (Corduliidae) includes medium-sized dragonflies, the color of which has a bright metallic sheen.

Small homoptera dragonflies: beauties, entrances and arrows

Family Beauty - Calopterygidae, Lutki - Lestidae, Arrows - Coenagrionidae

Near any stagnant bodies of water, the dryad lute (Lestes dryas) and a similar species, the bride lute (L. sponsa), which differs only in the structure of the genital appendages, are very common. Females are lighter in color. Like dragonflies, their small, poorly flying relatives -. predators, their main prey are mosquitoes and midges. Nymphs eat water fly larvae. The body length of small dragonflies is from 25 to 50 mm. They keep their wings vertical to their abdomen because they cannot spread them in a different plane. They themselves can become victims of large dragonflies, birds or even insectivorous plants. The related family of arrowheads (Coenagrionidae) includes graceful dragonflies up to 40 mm long, folding their wings at rest with a short pterostigma along the body. They have weak flight and preferentially stay in thickets of aquatic plants. More often than others, we see the blue arrow (Enallagma cyathigerum), which has pear-shaped blue spots on the back of its head.

The smallest dragonfly
... this is Agriocnemis paia from Myanmar (Burma). One specimen, kept in the Natural History Museum in London, during life had a wingspan of 17.6 mm with a body length of 18 mm.

Air and water predators

Dragonflies are aerial predators that hunt in the air, visually spotting potential prey; in order to catch it, dragonflies sometimes have to perform miracles of aerobatics. They often eat prey on the fly. Some species of dragonflies are excellent flyers and can be very difficult to catch. By eating mosquitoes, horseflies and other bloodsuckers, dragonflies bring great benefits. The development of all dragonflies necessarily passes through the aquatic stage - the nymph (this is the name given to insect larvae that have the rudiments of wings). Nymphs are even greater predators because they not only eat any prey that is smaller than them, but are able to overcome an enemy even as tall as themselves. They also attack aquatic vertebrates; small fish also cannot resist these predators. All dragonfly nymphs are voracious predators, capturing prey with a modified lower lip - a mask, which rapidly opens and is thrown forward, while the claws at its front end, like stilettos, penetrate deeply into the victim. When the mask is folded, the prey is pulled to the mouth and quietly chewed.

Larvae and nymphs

Dragonfly larvae and nymphs are found in all types of fresh water bodies. They can be found in ponds and rivers, drying up puddles, and even in tree hollows filled with water. The larvae of some species are able to survive in conditions of moderate salinity; other larvae lead a semi-aquatic lifestyle, crawling to the surface of the earth at night; they can be found along the banks of swamps and on the branches of half-flooded trees. Larvae of six species lead a completely terrestrial lifestyle.

During development, the larva molts from 10 to 20 times at the age of 3 months to 6-10 years, depending on the species. The number of moults depends on natural conditions and the availability of food. During the 6-7 molt, the wing rudiments begin to actively develop. Direct metamorphosis, bypassing the pupal stage, the adult insect leaves the water and sometimes moves a considerable distance from its place of birth. During its absence, which lasts several days, the dragonfly actively feeds and acquires physical maturity. A sign of the onset of maturity will be the bright color of the dragonfly. Young dragonflies are recognized by the glassy sheen of their wings. With age, the coloration of dragonflies becomes more intricate; additionally colored areas appear, which are absent in juveniles.

Lifespan

Most adults live a long time. In areas with a cold climate, dragonflies spend the winter, choosing secluded places for wintering; in the tropics, dragonflies wait out the dry season and come to life with the onset of rain. Some dragonflies undertake long flights, including along the transatlantic route, but most species live near their breeding sites

Pairing

During the mating process, the couple performs a complex trick. The male grasps the female by the head (genus Anisoptera) or prothorax (genus Zygoptera). The pair flies clinging (male in front, female in back), often they rest on bushes in the same position. The female bends her abdomen, forming a wheel, and connects with the secondary genitalia, located on segments 2-3 of the male, onto which sperm from the primary genital opening from segment 9 was previously applied. In different species, mating lasts from several seconds to several hours. Some types of dragonflies also lay eggs together, since by this time the male and female are not separated. In others, the male hovers over the female while she lays eggs. Still others The males leave the female amoi to handle this process: they either return to their area or sit on a bush nearby.

Gather in flocks

It is known that dragonflies (Odonata) can gather in flocks, the size of which in some cases can be considered huge. Thus, males gather in flocks and patrol breeding sites; they can sit on nearby bushes or fly up and down in search of females. The area where they gather is very small. The fact is that in many species, females stay far from water, appearing near a pond or lake only to mate or to lay eggs. In some cases, males and females stay in place and fly in one flock. For example, on June 13, 1817, dragonflies flew over Dresden for two hours. July 26, 1883 flock four-spotted dragonfly (Libellula quadrimaculata) flew over the Swedish city of Malmo from 7 hours 30 minutes. In the morning until 8 o'clock. Evenings. In 1900, a flock of dragonflies was observed in Belgium, 170 m long and 100 km wide.

Usually camouflage is associated with immobility, however dragonflies (Hemianax papuensis), those competing for territory, on the contrary, use movement to hide from each other. It turned out that dragonflies in flight concentrate their shadow in the enemy’s retina with the highest precision, and the absence of optical flow causes the enemy to perceive the dragonfly as a static object that does not pose a threat. How dragonflies manage to do all this remains a mystery.

Dragonfly flight speed– up to 96 km/h; bumblebee – 18 km/h.

Dragonflies V folklore different countries

In some countries (especially Japan), dragonflies are an image of beauty along with butterflies and birds. In European culture, the attitude towards dragonflies is less favorable. They are considered the “goad of horses” and the “devil’s sting.”

Of course, dragonflies can neither sting nor bite. All types of dragonflies are absolutely harmless. Moreover, they are beneficial insects because they destroy harmful insects. The presence of many dragonflies near a reservoir indicates its ecological attractiveness and the presence of many aquatic inhabitants in it.

Giant extinct dragonflies

Giant dragonflies that lived during the Cretaceous period had a wingspan of 0.7 m.

The morphological organization, which is characteristic of insects, provided them with fundamental morphological progress (aromorphosis). Based on this organization, they mastered the air-ground habitat. Subsequently, insects adapted to a wide variety of private environments, as a result of which they developed various specific adaptive adaptations (idioadaptations). Based on these adaptations in the past and now, insects are undergoing intensive speciation.

Paleoptera

Findings of fossil insects belonging to four extinct and two extant orders of Paleoptera indicate that the two surviving orders are Ephemeroptera (mayflies; Fig. 1, A And B) and Odonata (dragonflies) are but the remnants of Pennsylvania's ancient and highly diverse winged insect fauna. Modern orders represent two divergent branches of Paleoptera. In Ephemeroptera, the ability to fly at both the preimaginal and imaginal stages of development, as well as the reduction of the oral apparatus in these stages, which occurred in post-Paleozoic times, indicate their long-standing separation from other Paleoptera.

Rice. 1. Early representatives of the order Ephemeroptera.

A. Triplosoha pulchella from Upper Pennsylvanian deposits of Europe (from Riek, 1970, with modifications; after Edmonds, Traver). B. Protereisma regtspit from the Lower Permian of North America (from Rodendorff et al., after Tillyard).

Odonata have changed little since their origins, and perhaps their nymphs and adults have always been predators. In terms of the structure of the mouthparts, Protodonata are similar to active, fast dragonflies, but their body was much more massive. Judging by the appearance of the fossil nymphs of Palaeodictyoptera and Megasecoptera, it can be assumed that they were terrestrial insects, and their adult forms were herbivores. The significance of Paleoptera is that they became the ancestors of one, and possibly two groups of insects with the ability to fold their wings over their abdomen. This provided the wings with protection when they were not being used for flight, and significantly increased the mobility of individuals.

The most important group descended from early paleoptera is the group Neoptera. The wings of these insects, thanks to a complex system of wing articulated sclerites, can be folded on the back along the body. The wing articulations of the two modern orders of Paleoptera are completely different.

Orthopteroid orders

Among the orthopteroid orders, Dictyoptera (cockroaches) and Isoptera (termites) are considered the most primitive, and the wing venation of these orders is generally similar. The former was well represented in Pennsylvania by true cockroaches (suborder Blattaria), while the earliest records of termites date back to the Cretaceous. In the wings of Protorthoptera from Pennsylvanian and Permian deposits, variations in the number of anal veins, differences between the fore and hind wings, and different ways of folding the wings were found. The most primitive Protorthoptera from the early Pennsylvanian are the oldest known winged insects, the venation of their wings being a typical archedictyon. Protelytroptera appears to have shared a common ancestor with Dermaptera (earwigs); the latter are known from the Middle Jurassic.

The Orthoptera (locusts) and perhaps also the Phasmatodea (stick insects), Miomoptera and Caloneurodea represent clades that diverged early from one or more subgroups within the Protorthoptera. Phasmatodea are known from Triassic deposits of Australia. Representatives of Miomoptera and Caloneurodea, the first finds of which date back to the Pennsylvanian period, were already so specialized that their phylogenetic relationships are difficult to establish with certainty. The structure of the body and wings brings them closer to the orthopteroid orders. Orthoptera first appeared in Pennsylvanian sediments, and their wing venation has changed only slightly since then.

Another orthopteroid order represented in the fossil record is Embioptera. One genus of Embium was found in Permian deposits of eastern Europe (Fig. 2).

Rice. 2. Order Embioptera: Sheimia sojanensis from the Permian layers of the Arkhangelsk region (According to Rodendorff and others)

The rest date back to the Cenozoic era and were mainly found in Baltic amber; these forms are mostly similar to modern representatives of the order. The fossil forms of Grylloblattodea, a highly specialized order, are unknown.

Plecopteroid orders

There are very reliable finds of Protoperlaria and Plecoptera (stoneflies) from Permian deposits. These two orders of insects, whose nymphs lived in water, represent a small, distinct branch that split off from Protorthoptera. Stoneflies are known from Permian, Jurassic, Cretaceous and Cenozoic deposits.

Hemipteroid orders

All fossil hemipteroids belong to modern orders, among which only Zoroptera and Phthiraptera (lice) have no known fossil forms. Hemiptera (bugs) and Psocoptera (hay beetles) are well represented in the Permian sediments, and the appearance of Thysanoptera (thrips) can be reliably attributed to the Jurassic period. All Permian Hemiptera (Fig. 3) belonged to Homoptera (homoptera) and had a sucking proboscis, characteristic of this suborder. The extinct families of Permian Hemiptera are highly diverse, sometimes with long ovipositors, indicating their relationship to some ancient Orthoptera. They adapted perfectly to liquid food and, apparently, gradually replaced Paleodictyoptera from ecological niches with food of this kind.

In the Early Permian Psocoptera, belonging to the suborder Permopsocida (Fig. 4, A), both pairs of wings were almost identical, with simple venation. By the end of the Permian period, at least two families of the order Psocoptera already had reduced hind wings and modified venation of the fore wings (Fig. 4, B) ; these forms were surprisingly similar to modern hayeaters. There are few fossils of Thysanoptera, the best known are finds from the Jurassic deposits of Central Asia. Finds of insects similar to thrips are also known from Upper Permian deposits in the European part.

Rice. 3. Order Hemiptera: Permocicada integra from Permian deposits of the Arkhangelsk region. (According to Rodendorff et al.)

Rice. 4. Representatives of the order Psocoptera.

A. Dichentomum tinctum(suborder Permopsocida) from the Lower Permian sediments of Kansas, USA (according to Cagrenter). B. Zoropsocus tomiensis(suborder Parapsocida) from Permian deposits of the Arkhangelsk region. B. Lophioneurodes sarbalensis(suborder Parapsocida) from the Lower Permian, Kuznetsk basin (B And IN according to Rodendorff et al.).

Neuropteroid orders

These orders are very well represented in fossil forms. Both major branches of the neuropteroid orders first appeared in the Pennsylvanian and were numerous in the Permian.

Primitive neuropteroids. Of the primitive neuropteroids, the orders Megaloptera (boloptera), Neuroptera (retinoptera) (Fig. 16), Glosselytrodea and Coleoptera (beetles) appeared in the Permian period. The appearance of Raphidioptera (camels) (Fig. 5) can be reliably attributed to the Jurassic period. The abundance and species diversity of representatives of these orders was much greater in the Permian, Triassic and Jurassic periods than now.

Most families were formed before the end of the Jurassic period. Beetles are the only order of primitive neuropteroids to have colonized a variety of terrestrial habitats, and they currently make up almost 40% of all known insect species. The Permian fossil Coleoptera, which belonged to the suborder Archostemmata, already showed signs of venation characteristic of elytra. The Archostemmata dominated the Coleoptera until the Jurassic, when a large number of modern suborders and families emerged.

Rice. 5. Order Neuroptera: Mesypochrysa latipennis from Jurassic deposits of Kazakhstan (From Rodendorf and others)

Higher neuropteroids. These include Hymenoptera (wasps and bees), forming an independent branch; Mecoptera (scorpion flies), Siphonaptera (fleas) and Diptera (diptera), forming the second branch; Trichoptera (caddisflies) and Lepidoptera (butterflies), making up the third branch. Forms close to Trichoptera and representatives of Mecoptera are known from Permian deposits, indicating an even earlier separation of these branches, perhaps in Pennsylvania. Hymenoptega first appeared in the Triassic layers. In the Permian period, Mecoptera were already a fairly differentiated order and included at least three suborders. In one of them, Protomecoptera, the venation of the wings was similar to that of fossil insects similar to Megaloptera and living at about the same time, and of their descendants, representatives of the family Meropeidae, now a relict branch. The suborder Emnecoptera is represented in the Permian deposits by eight or more families (Fig. 6), most of which became extinct by the end of the Mesozoic or, having undergone strong changes, formed modern families. Two groups of Eumecoptera, which formed two distinct independent branches throughout the Mesozoic period, gave rise to two modern branches: 1) the family Bittacidae and 2) the families Panogridae and Panpodidae. The Mesozoic suborder Paratrichoptera existed in the Triassic, but was no longer found in the Cenozoic. The Permian and Mesozoic Mecoptera were much more diverse than modern Mecoptera, and from them two specialized orders, Siphonaptera and Diptera, emerged.

Rice. 6. Order Raphidioptera: Mesoraphidia pterostigmalis from Jurassic deposits of Kazakhstan. (From Rodendorff et al., after Handlirsch 1906-1908.)

Rice. 7. Agetochorista tillyardi- representative of the Permian Mecoptera (suborder Paramecoptera) from the Urals. (From Rodendorff et al., after Handlirsch, 1906-1908.)

Rice. 8. Flea Palaeopsylla clebsiana from Late Eocene Baltic amber. (From Rodendorff et al.)

The order Diptera contains more fossil forms (Fig. 8). Wings similar to those of Diptera have been found in Permian sediments of Australia and possibly in Triassic sediments. Diptera, very close to modern ones, are known from the Early Jurassic, where Nematocera and a number of families of Brachycera were widely represented. In the Eocene and in earlier layers, representatives of most families of Diptera were found. Representatives of the families of higher flies from the Schizophora group appear in the Middle and Upper Cenozoic deposits.

Rice. 9. Diptera Macrochile spectrum from Late Eocene Baltic amber.

Rice. 10. Order Hymenoptera. A. Anaxyela gracilis(suborder Symphyta from Jurassic deposits in Kazakhstan). B. Microtypus longicornis(suborder Apocrita, superfamily Ichneumonida) from Eocene Baltic amber; B. Cryptosegrhus pinorus(family Proctotrupidae) from Eocene Baltic amber. (From Rodendorff et al.)

Trichoptera (caddisflies) and Lepidoptera (butterflies) represent another group of neuropteroid insects that has greatly advanced in their evolution. Trichoptera or their immediate predecessors are known from the Early Permian of North America and the Late Permian of Australia. By the nature of the venation of the wings, they were similar to the ancient Mecoptera, which indicates their common origin. Permian caddisflies were an intermediate stage on the way to the Mesozoic representatives of this order; their cross veins and terminal branches were reduced. Representatives of the family Mesopsychidae were found in the Upper Triassic of Australia, and representatives of the family Necrotaulidae were found in the Upper Triassic and Lower Jurassic of northwestern Europe. In these families, independent bases near the veins are still preserved M and Cu 1. In later representatives of the order, the bases of these two veins are fused. Most other fossil records of caddisflies date back to the Cretaceous and Oligocene periods. Fossil finds of Trichoptera quite often preserve houses of larvae, the structure of which had apparently already developed by the Triassic period. The Lepidoptera order, well known to everyone for its huge diversity of large, brightly colored forms, is evolutionarily very young and relatively poorly represented in fossil finds. Several primitive families are known from Cretaceous deposits, but most fossil butterflies are from the Eocene and Oligocene of northern Europe (Baltic amber), and a few are from Oligocene deposits of North America. The suborder Jugatae was already well represented by the beginning of the Cenozoic. In terms of wing venation, its representatives are similar to some caddis flies and probably evolved from caddis flies in the Middle Mesozoic. In the more highly developed Frenatae, known from Baltic amber, the fore and hind wings were no longer identical. The most advanced suborder, Rhopalocera, has no fossil forms at all.

It is now believed that in addition to the numerous modern orders of insects, 11 or even more orders previously existed, judging by the fossil remains. Most of the extinct orders first appeared in sediments dating back to the Pennsylvanian or Early Permian and were mostly extinct by the end of the Permian. Among these extinct forms were the early ancestors of some modern orders of insects. Most of these fossil ancestors were morphologically more primitive and less specialized than their descendants; therefore, in the late Paleozoic, the differences between groups of insects were not yet as clear as between the corresponding modern orders. On the other hand, the study of late Paleozoic insects clearly shows that by the end of Pennsylvania the main stages of insect evolution were already completed. This applies to the development of wings, their folding, differentiation of feeding methods and the development of life cycles with complete transformation. Below are brief descriptions of those extinct orders of insects that have already been sufficiently studied.