Nomadic ants, regularly migrating in colonies of millions, live in the tropical zones of Africa, Asia and America. Insects do not build permanent nests; their sedentary phase of life lasts no more than 2-3 weeks. They move during the day, and for the night they set up a bivouac from their own bodies, in the center of which is the uterus. A horde that travels 1-3 km leaves nothing alive behind it. Powerful mandibles cut not only insects, but small mammals and birds. Stray ants are called killers, often exaggerating their danger.
Description
Several related groups of true ants share a similar lifestyle called the nomadic ant syndrome. Their characteristic feature is regular migrations. Numerous colonies of insects, reaching several million, move within 1-2 weeks. They carry eggs, larvae, and the queen with them. Nomadic individuals do not build anthills; by interlocking bodies, they build a nest for numerous family members and the queen.
Adult
The body of an adult ant consists of three sections: head, chest (mesosoma) and abdomen. The stalk connecting the thoracic segments and the abdomen is called petiole. The chitinous exoskeleton protects and supports the insect's body. On the ant's head there are antennae consisting of 8-10 segments. These are sensory organs that detect vibrations and chemical odors.
Interesting fact. Most wandering ants do not have visual organs or they are greatly reduced. Blind insects navigate in space using their antennae. They communicate with each other by releasing pheromones.
The upper jaws of mandible ants vary in size, but are always well developed. In working individuals, they are designed to carry eggs and larvae and food. For soldiers, this is a powerful weapon. Strong mandibles help tear apart enemies. Insects have 3 pairs of legs; their paws have claws that help them move along a vertical surface. The abdomen of some species ends in a sting.
Interesting fact. Soldier ants of the genus Dorylus do not open their closed jaws even after death.
Communication system
There are 75 glands in the ant's body; they secrete various substances, including pheromones and repellents. Nomadic species have dozens of special signal odors produced in various situations. With the help of pheromones, scouts indicate the direction of movement of the entire column and report the location of the prey.
Ant hierarchy
The nomad ant family consists of hundreds of thousands or millions of individuals. They all obey a strict hierarchy and act as a single harmonious organism. The basis of a large colony is made up of worker ants. These are infertile females. Specialized groups are formed from them: workers, foragers, scouts, soldiers. Males are several times larger than representatives of the working caste. The main figure of the family is the queen. She is the only female involved in giving birth to new members of the colony. The queen's lifespan is 15-20 years.
A significant part of the family is brood - eggs, larvae, pupae. The workers take care of him. In the family, responsibilities are clearly divided, each insect is busy with its own work. A highly organized colony is capable of building bridges and nests from the bodies of ants, resisting enemies, and hunting.
Classification
There are three subfamilies of tropical nomad ants in the world. The main classification occurs according to habitat:
- Aenictus are small to medium-sized insects common in Asia, Australia and Africa. Working individuals are yellow-brown in color, their body length does not exceed 3.5 mm. Males and females of the genus are much larger, reaching 25 mm. Differences are also manifested in the anatomical structure - in working ants the stalk between the chest and abdomen consists of two segments, in males and females there is one. The subfamily unites about 180 species.
- Dorylinae - main habitat regions are tropical Asia and Africa. The large group includes 800 species. The most famous genus is Dorylus. Depending on the hierarchy, ants vary significantly in size. Workers 3 mm, soldiers 13 mm, males 30 mm, females 50 mm. The number of individuals in one migrating colony is about 20 million.
- Ecitoninae - insects are found in the New World in the United States, the southern border of their habitat is Argentina and Chile. American raptors spend most of their lives traveling and hunting. During migration, places in the column are clearly allocated. Worker ants move in the middle and bear offspring. Soldiers on the sides protect their relatives from enemy attacks. The color of the imago ranges from brown to black.
Lifestyle
Nomadic ant syndrome manifests itself in the behavior and reproductive characteristics of insects. Its signs:
- collective foraging;
- construction of temporary nest-bivouacs;
- regular change of phases of settlement and migration;
- Subordination of the reproductive cycle to the colony's movement schedule.
With the onset of dusk, the construction of the bivouac begins. A temporary nest in the shape of a ball from the bodies of working individuals is built in a secluded place. The queen and offspring are placed inside. The bivouac has several entrances. The diameter of the bivouac is about 1 meter; it requires 500-700 thousand ants to build. African Siafu ants dig nests in soft soil. Blind mole rats quickly prepare a shelter for a huge family of up to 20 million individuals. Their distinguishing feature is the absence of a sting. It is replaced by powerful mandibles; painful bites cause discomfort even to elephants. The jaws easily cut the coverings of insects and animals and tear off pieces of flesh from them.
Nomadic ants at any age feed exclusively on meat. For small larvae, hunters hunt for spiders, caterpillars, beetles, locusts, and scorpions. Birds that make nests on the ground and small vertebrates (lizards, snakes, rodents) become victims of predators. The colony cleans the found corpses of large animals, leaving behind only bones.
Features of reproduction
The reproductive function of the colony is assigned to the queen uterus. Tropical nomad ants have one queen, while other species may have several. The large winged female mates with the male during her first flight. Until the end of her life, she uses up the stored sperm. The adult fertilized queen sheds her wings. She is always protected by working ants. During movement, the cylindrical elongated abdomen of the female is slender. As hundreds of thousands of eggs mature, it swells. By the beginning of the stationary phase, the larvae turn into cocoons and do not require nutrition. All the meat obtained by the hunters is given to the queen.
Ants are hymenopteran insects with complete metamorphosis. This means that their life begins with the egg phase, then the larva emerges. Ants turn into adults after pupation. The formation of eggs begins during the period of sedentary life. The fertility of a female is 200-300 thousand pieces. The embryonic period lasts up to three weeks. By the time of the new migration, larvae emerge from the eggs.
This process is synchronized by the development of pupae; adults emerge from the cocoons of the previous clutch. To feed the larvae, the colony sets off. By the time they pupate, the column finds a place to stay.
Once a year, the queen makes a special clutch from which reproductive females and males emerge. As they age, they leave the family and form their own colonies.
Benefits and dangers for humans
The beneficial actions of stray insects do not exclude danger to humans. Once on the path of the colony, a person risks being bitten by hundreds of individuals. Nomadic ants do not bite their prey immediately. They crawl under clothes in large numbers and act on a signal. For people prone to allergies, such an attack ends in anaphylactic shock. Attacks on people and animals are rare. The main prey of ants is other insects. Tropical wandering ants clear forests of animal corpses and destroy sick and weak individuals.
In Uganda, as in Africa in general, there are many diverse and interesting animals, including dangerous predators. Traditionally, everyone is afraid of lions or rhinoceroses, but it turns out that danger can lurk from much smaller creatures.
We climbed the steep paths of Mount Elgon, along which we were led by a great optimist and nature connoisseur, local guide Moses, or in Russian - Moses. Indulging in looking out for monkeys, turacos and other interesting fauna in the thick of the tropical forest, we didn’t really pay attention to what was going on under our feet. But suddenly Moses stopped us and nodded at our feet: be careful! What's happened? I looked at the path: it was crossed by a straight, like an arrow, and quite wide line.
Having looked closely, I realized that the line was constantly in motion, it was a continuous squad of ants marching through the jungle! Safari ants - that's what Moses called them. In Swahili, safari is nothing more than a journey, so in Russian the name of these ants sounds like nomadic or wandering ants.
They were called nomadic because these ants do not have anthills! They spend their entire lives in motion, carrying with them even the larvae, the queen and the eggs laid by her. Therefore, there is another name for these ants - army ants, because their movement is very reminiscent of an army on a march.
Just think - ants! But Moses' call for caution was not accidental. Nomadic ants are considered one of the most dangerous animals in Africa: if we were careless to stop right on their path, they would begin to quietly and imperceptibly crawl onto the body en masse, hiding under clothes, in shoes, in various secluded places. And we probably wouldn’t even notice them at first: unlike an ordinary ant, these ones don’t immediately try to bite the victim. Instead, they wait until they are in large enough numbers and bite them all AT ONCE, on a signal given by one of the ants! Of course, the march speed of ants is not that fast, only 20 meters per hour, but there are cases where ants killed and ate children or weakened people who, for one reason or another, did not manage to get out of their way in time. And small invertebrates, such as mice or frogs, regularly become prey for such ants, although, of course, they mainly feed on other insects.
In general, these ants of the genus Dorylus, which we met on a walk, are one of the most interesting in the world of ants, rich in incredible things. The size of their colonies reaches 22 million individuals, which is a record for ants. And their queens are the largest ants in size, 5-6 cm in length! When such a large unit marches, its width can be on the order of a meter. We, however, came across a much more modest group. If nomadic ants go through a village, local residents consider it best to get out of there for a while - but after returning, they can be sure that all other harmful insects, such as cockroaches, bedbugs, flies, mosquitoes, etc. houses were completely destroyed.
They also have an unexpected beneficial use, known among the Maasai from Kenya, neighboring Uganda (and they live on the other side of the same Mount Elgon where we walked). These ants are used as... surgical clamps! They are brought to the edge of the wound, there they bite through it, after which the ant’s body is cut off, and the jaws securely connect the edges until the wound heals.
It is interesting that these ants do not go out on reconnaissance missions alone, but divide into large groups, like a river in a delta, and lay out routes in search of victims, who are searched for by the release of carbon dioxide. We clearly saw this “branching” of them on the trail.
African termites.
Termites. Contemporaries of dinosaurs.
Termites are found throughout the African continent - in tropical forests, savannas, coastlines, mountains and deserts. True, they are rarely seen, because they are small in size and live secretly. That is why they are less known than elephants or ostriches. So it’s worth telling about them in more detail.
Family life of white termite ants.
Termites are popularly called “white ants”. Like ants, they live in large families. Left alone, the termite inevitably dies even in the most favorable conditions. Each family has at least one pair capable of reproduction, as well as their children - sterile worker termites and "soldiers".
The fertile female (called the &queen&) lays eggs. Lots of eggs! After all, the larger the family, the more successful it is. Most often, the queen is alone in the family. To fulfill its role, its abdomen grows so that the female becomes ten times longer than other termites. The female becomes so huge and heavy that she loses the ability to walk. She spends her entire life in a special cell where workers guard, feed and nurture her. If such a queen needs to be moved to another place, hundreds of them come running, otherwise they will not be able to raise her.
The female essentially turns into an egg-producing machine. Over the course of a year, she lays millions of them, in some species – every two seconds! In addition to such a queen and her “husband,” there are maturing males and females in the nest. They, the only ones in the nest, are winged and when the time comes, they leave it and found new families.
“Soldiers” are family protectors, mainly from ants. The soldiers have powerful, strong jaws, sometimes so large that they cannot be eaten, and the workers feed their defenders. A soldier with his wide head, like a cork, can completely block the enemy’s path in a narrow tunnel. If the wall of the outer tunnel is damaged, several soldiers block the gap with their heads. Many termites' "soldiers" shoot a fountain of poisonous or sticky liquid at the enemy. It also contains an “alarm substance” that mobilizes help - new detachments of soldiers. If a large gap appears in the wall of the nest, soldiers immediately run out of it and take up a perimeter defense. Meanwhile, behind them, workers are quickly clearing up the accident. True, by doing this they cut off the soldiers’ path back to the nest, and they are doomed to death.
Wooden diet.
In time immemorial, the ancestors of termites fed on dead organic matter - fallen leaves, humus soil (like earthworms), and manure. However, in nature there is a resource that is abundant all around, and there are only one or two people willing to eat it. This is dead wood. It consists of strong cellulose fibers, which are digested with great difficulty or even difficult for digestion. Termites managed to switch to this diet and escaped the fierce competition with numerous consumers of living plants. True, someone helped them in this matter.
As you know, even dead wood gradually rots - it is decomposed by bacteria, fungi and other microorganisms. Some, having got into the intestines of termites a long time ago, remained to live in it. The insect’s body gives them good protection from enemies, drought, etc. And for this they “undertook” to process lifeless wood into substances accessible to termites. As a result, both parties are full and satisfied. Some species of termites have become "farmers". In underground nests they set up plantations - they grow fungi similar to mold and feed on them.
A third, or even half, of a termite’s body weight comes from its beneficial companions. If you deprive him of these “tenants” and give him plenty of food, he will last for two weeks and die of hunger. Where do termites that have just hatched from eggs get them from? All family members feed their friend half-digested food. Newborns also get their share of food rich in beneficial microbes.
Home of termites, their fortress.
The ancestors of termites probably lived in rotting wood. It provided them not only with food, but also created a humid microclimate. Termites have thin body coverings, and in the open air the body easily loses moisture. This creates considerable problems for insects. After all, even the largest log is eventually eaten. You need to look for new food supplies and move to them. But running on the surface of the soil, under the rays of the hot sun, is deadly for termites. That's why they moved to live underground, in a permanent nest. And roads are specially laid for food. This way of life provided them with constant high humidity in the surrounding air and gave them protection from enemies - spiders, snakes, birds, and animals.
In some species, the nest is a system of chambers connected by passages. Other termites construct additional protection in the form of above-ground mounds or strong towers. Such a nest is more difficult to open from the outside; it helps maintain the desired microclimate. They layer sand grain by grain over a period of months and seal it with clay and saliva. The rains even out what has been laid. Sometimes pillars are built, surrounded by walls and covered with a common roof. There may be protrusions and holes for ventilation on the outside. There are soldiers guarding the construction site.
Inside the house there are rooms for the queen, for raising offspring, and a mushroom garden. Many chambers are separated by partitions made of chewed wood. In the tropics, monolithic pointed termite mounds up to 8–9 meters high are especially impressive! Scattered across the savannah, gray and red, they look like strange modern sculptures. In the old days, Africans opened such termite mounds and smelted metal in them. By the way, to crack them, you need a crowbar and remarkable strength.
Termite mounds are complex structures that have galleries, gentle descents-ramps, ventilation pipes, and outside shells for draining rainwater. In the Sahara, termite mound pipes reach groundwater. Descending into these “wells”, insects drink and carry the water up to give their relatives a drink. The nest is designed in such a way that stable temperature and humidity are maintained in the hatching chambers. On the roof of the house it can reach +50°, but inside it does not rise above +30°.
It's time to hit the road.
Often, “scout” termites discover deposits of food that cannot be quickly eaten. For example, a thick trunk of a fallen eucalyptus can reach and weigh tens of tons! Termites build stable roads to such a “dining room” - underground tunnels. Unlike our paths and tracks, termite tunnels are more or less straight, without sharp turns. This allows you to spend less energy when going for food and move faster. Builders compact and smooth the loose walls, lubricate them with a mixture of clay and saliva, and remove pebbles from the road. Moving along the road, termites leave odorous marks on it, which help those who follow to navigate in complete darkness.
It is not always possible to get to food from underground. Dry branches may be somewhere high up in the crown, firewood may be stacked in a woodpile, etc. In short, in order not to starve, termites have to leave their cozy dungeon.
At first, having come to the surface, the termite immediately returns, and soon soldiers appear from the tunnel, mobilized by the chemical signals of the scout workers. The soldiers mark the path and line up along the side of the road with their heads facing outward. Under this guard, the odorous path lengthens until it reaches its destination. A lively movement begins along it. Workers chew off grains of wood and carry them to the nest.
Sometimes such a road reaches a length of 50 meters. But termites feel uncomfortable outdoors. In addition, on a long road, no security can save ants and other predators from gangs. Therefore, termites use grains of soil moistened with saliva to build walls and roofs along the road. They compact and smooth them from the inside, sealing all the cracks. Soldiers guard the construction site - they stand on the walls until a roof appears over the highway. The result is a completely closed tunnel, similar to a thick cord. It stretches across the ground, dives into the grass, and climbs up a tree trunk. If a new food source is discovered somewhere on the side of the route, a branch tunnel is built to it.
Are termites allies or enemies?
People are wary of &white ants&. Termites destroy any wooden structures and objects. To protect wood, special impregnation or replacement is required - with stone, concrete, metal. Plus, termites, when building roads and tunnels, damage communication cables, rubber, film and plastic; in houses and warehouses they eat cardboard and paper (books, documents).
But in nature, especially in the tropics, termites are one of the main links in the cycle of substances. If it were not for these insects, the soil would be covered with a layer of fallen branches, fallen trunks, and this entire mass would lie for centuries as a dead weight. Termites quickly process it, returning useful substances to the soil, and they become available to other organisms. Termites mix the soil; through their tunnels, air and water, necessary for the inhabitants of the soil, easily penetrate into it.
...All over Africa - from the deserts of Algeria to the savannahs of Tanzania and South Africa - scientists are excavating the remains of huge dinosaurs. Termites are their peers. But unlike the terrible lizards, they have survived to this day and are thriving. And if not for these tiny creatures, the appearance of African nature would probably be different.
“We don’t abandon our own” - it turns out that not only people, but also insects can be guided by this rule. German scientists have shown that African termite-hunting ants pull wounded comrades from the battlefield and then nurse them to health. However, this behavior, one of the most impressive manifestations of mutual assistance in nature, is not related to moral considerations. Pure pragmatism - no sentimentality: abandoning their comrades to the mercy of fate, the ants would soon be left without workers.
The world's most widely read work on evolutionary theory, from the pen of a Russian author, was written not by a professional biologist, but by a professional revolutionary. This refers to the book “Mutual Aid as a Factor of Evolution,” which was published in London in the fall of 1902. Its author was political emigrant and anarchist theorist Count Pyotr Alekseevich Kropotkin. On the pages of his book, the count argued that Thomas Huxley and other Darwinists unjustifiably exaggerated the importance of the intraspecific struggle for existence. According to Kropotkin, the main role in evolution is played by the fight against unfavorable environmental conditions and other species - but among themselves, conspecific individuals (belonging to the same species) strive to establish cooperation, and the better this happens, the more successful this species achieves.
One cannot help but remember Kropotkin’s reasoning when getting acquainted with the discovery made by German scientists from the Julius Maximilian University of Würzburg. Watching the life of an African ant Megaponera analis of the subfamily ponerines, they encountered the first known case of caring for the wounded among invertebrate animals. Although the fact that ants help their relatives in trouble has been known for a long time. For example, they pull their comrades by the legs when they are caught in an antlion trap (see K. Miler, 2016. Moribund ants do not call for help). However, as it has now turned out, ants can take care not only of those who are in immediate danger, but also of those who have already suffered from the enemy. Pyotr Alekseevich would probably have mentioned this in his book.
Ants Megaponera analis live in sub-Saharan Africa and specialize in feeding on termites. Two or three times a day, these ants line up in columns of 200–500 individuals and go to destroy nearby termite mounds. The largest of them break open the shell of the nest with their jaws, the smaller ones rush inside, grabbing and killing its inhabitants. Then the robber caravan grabs the prey - killed termites - and goes home (Fig. 2).
However, the raiders encounter fierce resistance. Termite soldiers attack aliens, bite off their limbs and antennae, and also cling to them in a death grip. Therefore, many injured ants remain on the battlefield. The authors of the article noticed that the ant squad does not return without collecting wounded relatives (Fig. 1). To track their further fate (maybe the ants drag away the injured members of the nest to eat them?), scientists marked the wounded with paint. In total, they had to observe 420 forays made by 52 ant families.
It turned out that 95% of the defeated ants, which were carried away by their relatives to the nest, returned to normal life and participated in the following raids. Almost all of them were freed by their fellows from clinging termites - why not a kind of “medical care”? But those wounded, whom scientists did not allow to be taken away and therefore forced to return home on their own, did not reach the nest in 32% of cases - approximately half of them became victims of spiders (Fig. 3). It turns out that by transporting injured relatives, ants thereby protect them from predators.
The authors of the article calculated that if not for the operations to rescue the wounded, the ant colony would have lost an average of 28.7% of the workers. So for ants, who live by robbery and therefore often get injured, “compassion” towards the crippled and disabled is a necessary element of survival. Interestingly, thanks to peace and attention from their comrades, the ants recovered even after serious injuries. For example, an ant that lost two legs in a fight ran 32% faster a day after being in the nest than immediately after the injury, almost at the same speed as healthy individuals. Every fifth ant in the robber caravan has traces of such old injuries.
Since only 30% of the ants return with prey after a raid, there are always many free hands (more precisely, jaws) left in the column that could pick up wounded soldiers. That is, in order to save the wounded, ants do not even have to sacrifice provisions: the benefits of “humane treatment” of injured comrades are enormous, and the costs are minimal.
But how do ants understand that their comrade is injured and needs transportation? It turned out that when wounded, ants secrete a special secretion from the mandibular glands (see mandibles), consisting of dimethyl disulfide and dimethyl trisulfide. When scientists smeared healthy ants with these substances, their relatives picked them up and carried them, as if they were dealing with wounded ones. However, mutual assistance among ants is still not universal. For example, when researchers artificially damaged ants in a column along its path to a termite mound, that is, before the battle, the ants did not pay attention to the victim. It turns out that ants are programmed to help their relatives only in a certain context - on the battlefield.
Why don’t other ants practice similar behavior? According to scientists, it's all about fertility: Megaponera analis it is low, on average only 13 new ants are hatched per day in their nest. So they cannot act on the principle “the squad did not notice the loss of a fighter.” But, for example, nomadic ants, whose colonies consist of hundreds of thousands and millions of individuals, have a colossal birth rate, and they may not pay attention to the wounded and stragglers.
Source: Erik Thomas Frank, Thomas Schmitt, Thomas Hovestadt, Oliver Mitesser, Jonas Stiegler, Karl Eduard Linsenmair. Saving the injured: Rescue behavior in the termite-hunting ant Megaponera analis // Science Advances. 2017. V. 3: e1602187.
Alexander Khramov
"Elements"
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Kipyatkov V. E.
The brochure is devoted to the problem of the origin of social behavior in insects. The main stages of the evolution of parental behavior in insects and the emergence of truly social behavior on its basis are considered. The history of the formation of modern scientific ideas about the causes of sociality is outlined, the main theories that claim to solve this problem are critically examined, and an attempt is made to create a synthetic theory.
Until recently, it was believed that eusociality - that is, a form of social life of animals in which in the adult part of the population there is a caste of breeding individuals and a caste of non-breeding individuals serving it - could arise only as a way of maintaining close relatives. However, scientists from Harvard University have proposed a new theory according to which eusociality can also arise through the cooperation of unrelated individuals. Much more important are the characteristics of the life cycle and behavior of those animals that are, in principle, predisposed to the possible development of eusociality in the course of their evolution.
Ant circles (ant circles, death spiral, carousel of death, English Death mill) are a natural phenomenon consisting in the fact that one or a small group of ants, at first glance for no reason, begins to run in a vicious circle, gradually involving everything in its endless cycle more and more other ants. The ants continue their run until they drop dead, and the ant circle continues its rotation until it is completely exhausted, leaving hordes of dead in its wake.
It turns out that ants, “enslaved” to stronger species, are not as helpless as they might seem at first glance. Research results obtained at the Johannes Gutenberg University of Mainz (Johannes Gutenberg-Universität Mainz, Germany) indicate that enslaved ants carry out “actions of civil disobedience”, neglecting their direct responsibilities, even killing the descendants of their tyrants. Thus, they prevent the possibility of enslaving the next generation of similar ants.
Brian M.V.
The book offered to the reader by the famous English scientist M. Brian occupies a special place in the literature on social insects. This book is written for zoologists and ecologists who are not specifically involved in this problem. It discusses in detail the relationships of social insects, both among themselves and with other organisms.
This text is about ants. About how they organize their community, how they choose a profession, how they show genius, ingenuity, and heroism. And this is a text about people. Because whenever we talk about animals, even the smallest ones, we mean ourselves.
Alexander Markov
The gene required for the formation of eggs in insects also performs a number of other functions in the honey bee related to social organization and division of labor. The protein encoded by this gene influences the age at which a worker bee transitions from housework to foraging, whether it forages for nectar or pollen, and its lifespan.
Elena Naimark
A new study of the development of eusociality in bees is based on a comparison of genes that work differently in two bee castes. It turned out that genes that are expressed more in the working caste have undergone strong positive selection. The intensity of selection among the active genes of the worker caste turned out to be higher than for the active genes of the queens. This means that for kin selection, both individuals that reproduce and those that do not reproduce themselves, but only contribute to the survival of sisters and brothers, are important, and childless individuals are even more important for selection. The kin selection hypothesis thus received another powerful confirmation.
Elena Naimark
It is known that in higher vertebrates, care for offspring is passed on from generation to generation. Both genetic and epigenetic mechanisms of inheritance, as well as learning, are involved here. As it turned out, in insects the level of care towards young people is also inherited, and here the main role is played by learning and epigenetic inheritance, rather than genetic inheritance. Regardless of the existing genetic properties, if the mother earwig was responsible for the young entrusted to her, then the offspring grew up with an increased level of care, continuing the given trend of parental care.
For several decades now, debates have raged among biologists about the reality of group selection and its significance for evolution. Experiments on the social spider Anelosimus studiosus showed that in this species there actually is selective survival and selective reproduction of groups (colonies) depending on their hereditary properties, that is, group selection in its purest form. When there is a lack of food, colonies in which the proportion of aggressive individuals decreases as their numbers increase survive and reproduce better, while in abundant areas, colonies in which the proportion of aggressive individuals increases with increasing numbers survive and reproduce better. Under the influence of group selection, spiders have developed a genetically determined ability to regulate the quantitative ratio of aggressive and peaceful individuals in their groups in accordance with local conditions.
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