Why do ants move dead ant bodies

Ants are actually not really garden pests. Only the fact that they protect aphids from other insects earns the ants this reputation. If they occur in large numbers, ants also appear threatening to many people. When the supposed garden pests also appear in the apartment, the fun is usually over. If you want to fight the ants, all of their loopholes must be found and closed. Alternatively or in addition to this, cans containing poisoned attractants can be distributed. If you attach rings made of glue to tree trunks, the ants will stick to them. Ants are particularly useful because they eat caterpillars and other garden pests. Ants (Formicidae) belong to the state-forming insects and represent a family within the hymenoptera (Hymenoptera).

Generally

Around 12,500 species are known, 180 of them in Europe. The most well-known species found in Germany include the red wood ant and the black garden ant. Ants are found in almost all regions of the world, so they can also be found in the Arctic Circle, in the high mountains and in the desert. Exceptions are Iceland, Greenland, Antarctica and parts of Polynesia. They are particularly numerous in the tropical rainforests. Fossils have shown that ants have existed since the early Cretaceous, around 130 million years ago.

A typical ant colony consists predominantly of sterile females and can contain several million individuals. In addition, there are one or more queens in each colony who play the reproductive role. The winged male individuals only have the task of mating the winged young queens during the wedding flight. The workers are usually much smaller than the reproductive individuals and are wingless. They have poison glands on their abdomen, which in many species lead to a poison sting. Often, however, this has receded or is completely absent. The ability of ants to smell and taste is comparatively highly developed. Communication with other individuals takes place, among other things, via pheromones. There is a division of labor among the animals and there are, among other things, brood keepers, nest builders and foragers. Ant colonies are generally extremely aggressive towards neighboring states.

The term "ant" comes from the old high German âmeiza (the cutter).

anatomy

An ant's body consists of three visibly subdivided segments, the head (caput), the mesosoma (breast segment) and the metasoma (abdomen).

The head

There are two antennae on the ant's usually round head. With the help of more than 2000 sensory cells, these sensors can perceive air currents, temperature fluctuations and smells. They usually consist of twelve segments in females and 13 segments in males and are angled in the middle so that their tips can be easily led to the mouth opening.

The ants' organs of vision are compound eyes which, like all insects, consist of ommatidia, which are each composed of eight sensory cells and which are arranged in a rotationally symmetrical manner in the ants. This means that ants can also perceive the polarization of light. Genera such as the Ponera from the subfamily of the ancient and stinging ants or Solenopsis of the knot ants have no more than 15 to 30 ommatidia per head side. Scale ants, on the other hand, have up to 30,000 ommatidia on each side. As a rule, ants are seldom able to recognize more than light-dark differences. Ant species are known that have no organs of sight.

The mouthparts are divided into the upper lip (labrum), upper jaw (mandibles), lower jaw (maxillae) and lower lip (labium). The mostly shovel-shaped and toothed mandibles are universal tools. They are equally suitable for crushing and transporting solid materials, as well as for fighting enemies.

The mesosoma

The mesosoma, sometimes called alitrunk among ants, consists of the chest area (thorax) and the first abdominal segment (propodeum).

As with all other insects, the thorax is divided into three segments, each with a pair of legs. They are referred to as the front chest (pronotum), middle chest (mesonotum) and rear chest (metanotum). The propodeum, also called epinotum, is, as with all waist wasps, firmly fused with the metanotum.

The legs, which consist of five limbs, have two claws on the last of these limbs and an adhesive device in between. The former enable a secure hold when moving on a rough surface. In contrast, the adhesive device prevents slipping on smooth surfaces. The ant's front legs also have a cleaning device with which it can brush off dirt particles from the feelers.

The metasoma

The metasoma consists of one or two pedicle members and the adjoining gaster, which is sometimes incorrectly referred to as the abdomen. Between the mesosoma and the gaster there is either one stalk member (petiolus) or two stalk members (petiolus and postpetiolus). This creates constrictions that function as joints between the body parts. This is followed by the rest of the abdomen (gaster).

The stalk link

In contrast to many other insects, ants have a stalk link (petiolus) that connects the mesosoma and the guests. The stalk link is actually the second abdominal segment. In some subfamilies, the third abdominal segment is also formed into a small stalk (postpetiolus).

The division into subfamilies is made on the basis of the pontic in connection with the number of abdominal segments:

  • Stinging ants (Ponerinae): an intermediate link, an additional noticeable indentation between the first and second segment of the abdomen
  • Glandular ants (Dolichoderinae): an intermediate limb, plus a four-limbed abdomen
  • Scale ants (Formicinae): an intermediate limb, plus a five-limbed abdomen
  • Knot ants (Myrmicinae): two intermediate links.

The stalk link enables strong movement of the abdomen. This can be bent down to enable the targeted spraying of defense secretions in dangerous situations. Ants can expel their substances up to a meter. The stem can also be directed almost vertically upwards together with the gaster. This attitude is mainly adopted when dispensing fragrances. One speaks of the so-called Sterzeln. Last but not least, the mobility of the abdomen makes it easier to clean the back of the body with the mouthparts.

The guests

The Gaster consists of several segments - body half-rings on the stomach and back, which are connected to one another by elastic skins and can thus be pushed into one another. This mechanism can greatly increase the number of guests.

Many of the glands are also located in the gaster, which mainly contains the goiter (a bulge in the ladder of food that is used to store food), the stomach, the intestines and the gonads. The stomach lies in the front part and is connected to the midgut by a valve-like structure, the so-called valve funnel. When the valve funnel is open, food can pass from the goiter into the midgut. Only a relatively small part of the food stored in the goiter goes this way. The main part is pumped back from the crop to the mouth opening and shared with other ants. One therefore also speaks of the social stomach.

Glands and secretions

Most of the glands are grouped into larger complexes in the inter-segmental membranes of the abdomen. These glands are usually equipped with a specially structured reservoir. The sternal and pygidial glands produce a wide variety of trace scents (pheromones) that facilitate communication between the ants.

Other trace pheromones are provided by the poison and Dufour's glands in ants, and a tibial gland in the Crematogaster genus. Glands are also located within the body, head, thorax, and gaster. The only glands that do not supply pheromones are the food glands leading into the mouth area. The metathoracic gland supplies bactericidal and fungicidal substances. The leaf cutter ants contain a disinfectant (mostly phenylacetic acid or hydroxyhexanoic acid) in order to prevent unwanted fungi and bacteria from growing. What is remarkable about the secretions is that the same substances have different effects in different situations, whereby the same glands can produce different substances in different species. In male horse ant males, for example, the mandible gland provides a pheromone that stimulates the females to mate, while in other species it produces a corrosive defensive secretion.

The chemical structures of many pheromones are now known. As with formic acid, these are mostly simple compounds (e.g. alcohols, aldehydes, fatty acids or esters). However, there are also more complex compounds, such as various terpenoids and alkaloids. Determining the secretions is difficult because many glands only release very small amounts of secretion. The mixing ratio of different secretions is often important for a certain effect. An example of this is a substance from the common turf ant (Tetramorium caespitum), in which two pyrazines only trigger the desired effect in a ratio of 7: 3.

Many ants, for example the weaver ant Oecophylla longinoda, release substances that act in different ranges. This way, other ants can be led to a specific spot. In case of danger, the lawn ant first releases a very volatile secretion from its mandible gland, a hexanal, which begins to act after about 20 seconds within a radius of about ten centimeters. At the same time, conspecifics that are closer to the scene are warned by 1-hexanol, which only reaches half as far. The ants that are closest to it are stimulated by 3-undecanone and the least volatile 2-butyl-2-octenal to attack the opponent immediately.

All pheromones are very well adapted to their function. Alarm pheromones must evaporate quickly, while trace pheromones, on the other hand, have a very long life. The scent trail of the glossy black wood ant (Lasius fuliginosus) contains a mixture of fatty acids and hexanoic to dodecanoic acids and works for weeks. The most important function of the fragrances in ants is their so-called nest odor. This smell is characteristic of all ants in a colony. In this way, they can differentiate between different states of the same species based on their “scent uniforms”.

Some glands are on the sting; With one bite, different poisons are released depending on the species. The sting was regressed in many species of ants in the course of evolution, but all species of ants retained these poisonous and Dufour's glands. The poison gland of the red wood ant can contain up to 6 mm³ of various poisons, including 60% formic acid. Formic acid vapors act like a breath poison in small animals and can also be fatal.

Genital organs

Ants are of separate sex. The males have two testicles and two sperm ducts in the gaster. The paired ovaries of the females are also located in the rearmost part of the body. However, in most species only the queen can lay eggs, since only she was fed the hormones necessary for sexual maturity as a larva. The workers have no or only stunted sexual organs. They can only produce eggs for male sex animals, if at all.

Excretory organs

The ants' excretory organs (Malpighian vessels) are thin tubes that protrude into the body cavity (Mixocoel) free of filter options. The waste products are discharged from the cells into the Malpighian vessels and then enter the intestine. This is where reabsorption takes place, i.e. water and usable substances are returned to the bloodstream.

food

Omnivores

Probably the best-known native ant species, the red wood ant, is omnivorous. Their diet consists mainly of insects (e.g. caterpillars, butterflies, flies) and other invertebrates (e.g. spiders). In addition, excretions from various types of louse (honeydew), secretions from floral and extra-floral nectaries, as well as seeds, pollen, fruits and various parts of plants are eaten. If an individual worker encounters a prey that is too large (for her alone), she usually attacks it anyway and tries to inflict a wound on it with the jaw pincers, into which she sprays formic acid from the poison gland. The highly volatile formic acid signals to conspecifics that support is needed.

Predators and scavengers

A number of species of ants - for example driver ants - feed exclusively in a predatory manner. In addition, some species also feed on fresh carrion. Some species of ants have specialized in certain prey animals, for example the South American knot ant genus Dacetone feeds exclusively on springtails.

Ant species that live nomadically, such as the driver, wandering and amazon ants, hunt as a whole colony. The wandering ants, for example, form fronts that can often be 14 to 20 meters wide. In addition to various invertebrates, they also occasionally prey on nestlings, small mammals and snakes.

Use of plant-sucking insects

Many species of ants live in symbiosis with plant-sucking insects and thus in mutual dependency.

The main ones are phloem-sucking scale insects (Coccoidea), aphids (Aphidoidea) and leaf fleas (Psylloidea). Phloem is high in carbohydrates but very low in protein. Phloem suckers therefore only consume about ten percent of the carbohydrates; the excess is excreted as high-sugar honeydew - the ants' most important source of carbohydrates.

The ants “milk” the leaf suckers and in turn guard them from predators. Some species of ants let the aphids overwinter in their nest or carry their eggs into their nest to protect them from the cold. Larvae washed away by the rain are searched for and brought back by the ants.

Some ants look specifically for leaf suckers and move them to plants preferred by the plant suckers. If a herd becomes too large, the ants drive or carry the lice or their eggs to a new plant. Wars have been observed between different ant colonies, in which they fought for supremacy over herds of lice.

Seed eater

The harvest ant species (granivores) of the genus Pogonomyrmex that occur in the semi-deserts and steppes, or the Messor, which is widespread in warmer regions of Europe and Africa, collect mainly grass (for example cereal), but also other plant seeds, which they store en masse and from them they only feed themselves. Among the harvest ants there are workers with enlarged mandibles (so-called majors) who only crack the seeds that are dragged along the up to 200-meter-long ant trails. Less specialized harvest ants such as representatives of the pheidole or tetramorium do not depend on plant seeds and also use other food options.

Seed collector

This group includes the eliosome-eating ants, e.g. B. most wood ants and garden ants. The elaiosome is a protein and fat-rich eating body that is found as an appendage to the seeds of herbaceous plants that grow close to the ground (such as various types of violet and lark spur). The seeds spread on these plants by ants (myrmecochory). The mostly very small seeds are transported away as a whole and therefore distributed, but only the elaiosome is used.

thieves

Thieves or occasional thieves build passages in foreign nests or even brood chambers and kidnap the foreign brood in order to consume them later. This kleptoparasitism was observed, for example, in the pharaoh ant (Monomorium pharaonis) and the yellow thief ant (Solenopsis fugax), which were introduced into Europe and have to be registered in several countries.

Mushroom grower

Some species of ants in the Attini tribe grow mushrooms. These include the South American leaf cutter ants of the genera Atta and Acromyrmex, which mainly breed umbrella mushrooms (Lepiota) in their nests up to eight meters high and live with these and a bacterium in a rare triple symbiosis.

The ants bring in leaf and plant parts, chew them up to a pulpy, largely fungicide-free mass, which then serves as a special breeding ground for the fungi. In contrast, the fungi form protein-rich thickenings (gongylidia or bromalia) at the ends of the fungal threads, which serve as a source of protein for the ants. The fungi also break down the cellulose in the plant materials in such a way that they can be used by the ants and also break down insecticides. The third in the triple symbiosis are bacteria of the genus Streptomyces, which have their habitat on the underside of the ants and produce antibacterial and fungicidal substances. In this way, the ants protect their fungi from highly specialized parasites such as the Escovopsis species belonging to the hose fungus, which threaten the ants' harvest.Some Attini species grow mushrooms on caterpillar droppings or other organic materials.

The ant colony

The ants are among the eusocial (state-building) insects. In ants there are states of only a few hundred (leptothorax) to over 20 million animals. The largest known ant colony was discovered by the Swiss biologist Laurent Keller. It extends over a length of 5760 kilometers along the coast of the Italian Riviera to the north-west of Spain and consists of several million nests with several billion individuals. Normally the ant colonies would attack one another unless they are so closely related that they recognize and accept one another as one colony. In the foreseeable future, however, the genetic relationship of the individual sub-colonies of this super colony will decrease to such an extent that the ants will no longer recognize each other.

Monogynous states, which therefore only have one queen, can usually only live as old as the queen herself, since eggs are no longer laid after her death. Queens, such as those of the red wood ant (Formica rufa), can live up to 25 years, while the workers rarely live longer than two to three years. In the case of the black garden ant (Lasius niger), the average life expectancy of the queens is estimated at 29 years.

Polygyne states can contain two to 5000 queens. These states typically live to be 50 to 80 years old. Then the phenomenon occurs that the queens no longer accept each other, as the degree of kinship is getting smaller and smaller.

Reproduction and caste formation

Types of gender

The typical insect state consists of individuals from different castes, almost without exception females: queens as well as workers or soldiers. The ants with the typical royal shape, the full females (gynomorphs), usually shed their wings after mating and then differ externally, among other things. in size from normal workers. A reliable feature for recognizing a queen is the so-called "queen hump". However, there are also small dwarf queens (microgyne) that keep their wings in the socially parasitic species. Queens with typical worker form are the ergatomorphs. In many ant species there are intermorphic females that are anatomically an intermediate form (no wings, but fully developed gonads). All three forms can theoretically function as both a queen and a worker.

In addition, there are very many species of ants with reproductive workers who have poorly developed gonads, slightly underdeveloped egg tubes and usually no or a severely reduced seed sac (receptaculum seminis). For example, they are used in monogynic states when the queen dies. Since workers are not mated, however, they cannot fertilize their eggs, and these therefore come about in a unisexual (parthenogenic) way. That is why the female workers only ever produce males.

In addition to the workers and queens, there are also the winged males. You can see them on their wedding flight in spring. Males only arise to mate the young queens.

Egg laying

After hibernating, the queen warms up for three to eight days and then begins to lay eggs (several hundred a day, up to 300 in the case of the red wood ant). In most species it is first and foremost the eggs of sex animals (males or young queens), since late-hatched queens have little chance of founding a new state and thus preserving the species.

Like all colonizing hymenoptera (Hymenoptera), ants have no sex chromosomes. The queen can decide whether an egg should become a female or a male, depending on whether or not she sprays the egg in her egg ladders with a sperm syringe. It is still unclear how the Queen will make this decision.

Sometimes there are also queen eggs (using the example of the small wood ant). They are much larger because they contain a special RNA protein food, the pole plasma, at their posterior pole, which the embryos need to develop into queens.

Some species of ants (such as the weaver ants of the genus Oecophylla) lay trophic eggs. These eggs are not laid to produce offspring, but serve as feeding eggs that the larvae are later fed with.

Egg care

Ant eggs are mostly soft-shelled, elongated ellipsoids up to one millimeter in length. After the eggs are laid, the brood carers use their mandibles to carry the eggs into the brood chambers, where the appropriate temperature and humidity prevail. If this microclimate changes due to external influences (e.g. destruction), the eggs are immediately transported by the workers to other incubators.

The brood carers lick and spit on the eggs again and again in order to keep them clean and to protect them from drying out. The eggs also stick to each other and can therefore be transported as "packages" if necessary.

In some species the workers eat a few unfertilized eggs if too many males would otherwise arise.

The development of the eggs in ants takes between one and four weeks, depending on the species, and around two weeks in the case of the red wood ant.

cocoon

After a while, the white or yellowish, maggot-shaped larvae hatch from the eggs. They are soft-skinned, usually slightly hairy and, depending on the species, more or less mobile. Legs, eyes and mouth parts are not yet developed, the digestive organs are only partially developed. Brood carers transport the larvae into the sun, feed them through their crop and clean them so that they do not dry out or grow fungus.

In most ant species, the food of the hatched larvae and their position in relation to the queen are important for sex formation. The larvae of queen eggs can develop into workers with the wrong food, and queens with the right food can develop from those normal eggs. The correct food is queen jelly (a normal goiter food to which a secretion from the labial and postpharynx glands is added), which the brood keepers feed to the larvae by "goiter-to-mouth" (throphallaxis). The food factor in the development of the queen is called the trophic factor. All eggs (including queen eggs) that are very close to the queen develop into workers. This is explained by the fact that the queen controls the crop feed of the brood carers via a certain sprayed scent.

For morphological reasons, there may be two to three sub-castes within the worker caste, such as small and large workers or soldiers. Soldiers (for example the driver ants) have a greatly enlarged head with very large mandibles. The so-called honey pots of the North American honey pot ant genus Myrmecocystus, the scale ants and, in a weakened form, the southern European species Proformica nasuta, in which animals act as food stores: their goiter fills the entire guest and is filled with honey. The definition of these sub-boxes also results from the food.

The males also receive a special diet.

Since the digestive organs are not yet fully developed in the larvae, they collect the indigestible food residues in the so-called head sac, which is located at the end of the midgut. Only at the end of the larval period is the connection to the anus fully established, so that the contents of the head sac can be disposed of as so-called meconium when it is transformed into a pupa. In such ants, whose pupae lie in cocoons, the larval excrement (excretion) becomes visible through black dots on the pupal shell as soon as a connection has been established between the intestine and stomach.

The larvae usually develop quickly. The larvae of the red wood ant can pupate within eight days. As with all holometabolic insects, the entire growth of ants is limited to the larval stage.

Ant pupae

In the pupal stage, the ant takes no more food and remains completely motionless. When pupating, the larvae of most scale ants and primeval ants spin themselves into a dry shell (cocoon) by means of a spinal gland secretion emerging from their labium. The larvae of the knot ants, however, pupate without a cocoon.

The pupal rest lasts around 14 days in the red wood ants, but significantly longer in many species. The pupal cocoons are transported to the most favorable locations and cared for by the brood carers. They also help with hatching and feed and clean the young ant for a few days until its chitin shell has hardened and darkened.

Once the young queens and males have hatched (in the case of the native species at the beginning of May), the entire state prepares for the wedding flight. The winged sex animals increasingly feel the urge to climb high points such as blades of grass, hills or trees. Special workers take care that the sex animals do not move too far from the nest and bring them back into the burrow if necessary.

At a species-specific point in time (for native species mostly in early or midsummer), which presumably depends on certain air currents, light conditions and temperatures, all sex animals of a species swarm out at the same time for their wedding flight. With this simple but ingenious trick, inbreeding can be avoided as far as possible. The opposite sex is attracted by the release of sexual fragrances.

On the wedding flight, which lasts a few hours, the young queen is mated by two to 40 males. The queen takes in up to several 100 million sperm in her semen sac, which she can store undamaged for an average of 25 years and with which she fertilizes the eggs. Especially tropical and subtropical species swarm twice a year.

A few hours after the wedding flight, the males die and are regarded as food by the workers and brought into the burrow. When the queens fall back to earth, their wings usually break in predetermined places or they bite off themselves since they are no longer needed.

Some, especially larger species of ants, mate on the ground.

After insemination, the queens try to raise their own colony of workers.

State development

Independent establishment of a state

The most common variant is the independent establishment of a state. It is operated by an estimated 65 percent of the species in Central Europe. In this form, a mated female looks for a suitable nesting place, creates a small, closed cavity, the Claustra, and lays her eggs there. The brood is fed and cared for by her completely independently. When establishing an independent state, a distinction is made between claustral (without feed intake) and semiclaustral (with feed intake) foundation.

Most species, especially the larger ones, do not need to forage during the breeding season. Initially, the queen feeds the larvae trophally. When her goiter food is used up, she breaks down her fat reserves and strong flight muscles, which she no longer needs after the wedding flight, and is thus able to produce food secretions for the larvae. If that is not enough either, she will eat part of her eggs in order to use them again and to ensure that at least some workers can develop and thus help in foraging for food.

In the smaller species, such as the Leptothorax genera, the young queens do not have enough body reserves, so they have to go looking for food every now and then. Since they have to expose themselves more than the larger species to the danger of their unguarded brood or themselves being eaten, only a few of the thousands of swarming young queens succeed in founding their own state.

With the first hatched workers, the new state is slowly being established. The queen no longer takes care of the offspring, rather she devotes herself exclusively to laying eggs. The workers now take on all other tasks, be it brood care, foraging or nest building. Such a state can also be founded jointly by several queens, whereby they all lay their eggs together in one place and let the brood raise together. The resulting state is then either polygynous or the queens decide by fighting over the hierarchy, if not one queen kills all the others, from which a so-called functional monogyny then arises.

Nest division

When the nests are shared, the newly mated queens come back to their nests after the wedding flight and spray a certain secretion that causes some of the workers to follow them. This creates daughter nests (sociotonia) in the vicinity of the original nest, which mostly remain connected by ant trails. Several ant nests in the immediate vicinity usually indicate a common original nest. Such a system is called a colony, and very large colonies, such as that of the Argentine ant, are called a super-colony.

Nest divisions were observed in almost all ant species, but mainly in the dwarf ant species of the Plagiolepis, the Kippleib ant (Crematogaster scutellaris) and the pharaoh ant (Monomorium pharaonis) introduced to us.

Return of the queens

Queens of the bald-backed wood ant and the great meadow ant often return to their home nest. There they are safely accompanied and cared for by workers in the building. The new queen then also begins to lay eggs. Colonies of this species often have several queens, so they are polygynous and split up when they get too big. The new queen then leaves the nest with some of the workers and establishes an “offshoot nest” (branch nest formation). It also happens that queens of these species do not find their way back to their old nest or are not accepted. They then try to be taken in by colonies of the same species (adoption), or try to penetrate a nest of closely related species, kill the queen there and have their offspring raised by the strange ants (temporary social parasitism).

The young queen of the red wood ant (Formica rufa) from a monogynous nest cannot return to the mother colony, but invades the state of the gray-black slave ant (Formica fusca), kills the queen and takes her place. The slave ants then raise the brood of the new queen. For some time you have such a mixed population, until the last slave ant has died and only the offspring of the new queen are left. If the young queen comes from a polygynous nest, she can also be adopted by the mother colony or another colony of the same species.

Social parasitic ants

Forms of enslavement can be found in the Amazon ant (Polyergus rufescens) in the species Leptothorax, Formica fusca, Formica sanguinea and Formica rufibarbis or in the Epimyrma ravouxi.

When a dependent state is founded, a queen looks for workers of the same or foreign species. In the special case of the blood-red predator ant (Formica sanguinea), the queen looks for an auxiliary queen, mostly with the gray-black slave ant (Formica fusca) or the red wood ant (Formica rufa). She intimidates the auxiliary queen and lays eggs in her burrow. The auxiliary queen then takes care of both clutches. When the dependent queen's first workers have hatched, the auxiliary queen is killed and her brood enslaved, so that the queen can now be looked after by the other workers. This type of dependent state formation is called temporary social parasitism. Every now and then it happens that the parasitic queen lets her host live and thus a permanent or temporary mixed colony develops (for example with the saber ant (Strongylognathus testaceus) and the common turf ant (Tetramorium caespitum).

Another type of social parasitism, the brood parasitism, is found in the workerless parasite ant (Anergates atratulus). It penetrates queenless nests of Tetramorium species and lays a large number of eggs there, which are "adopted" by the host ants.

Some species of ants are not able to eat independently or carry out nest building activities. They invade nests that are alien or of their own species and either kill all ants living there in order to use their burrows for their own people, or leave only the larvae that are soon to hatch intact to raise them as slaves. Most of the time, raids are undertaken in this form in order to constantly get new slaves.

Ants and the theory of evolution

The workers of the ants are altruistic creatures: while they do not reproduce themselves, they “selflessly” work to ensure that the queen can pass on her genes to offspring. Darwin was aware of the dilemma for the theory of evolution: How are altruistic genes passed on if their carriers - the workers - never reproduce. His attempt to explain: Complete family groups could also benefit from the selection. In 1968 the British biologist William D.Hamilton developed his mathematically supported and generally accepted theory of kin selection. Due to the special reproduction of state-building insects, ant workers are 75 percent related to each other, i.e. more than would be possible with their own daughter. That is why natural selection prefers those genes which induce workers to raise sisters and not daughters of their own - the basis of the altruistic social ant state.

The organization of the ant colony

orientation

In addition to using pheromones, ants can also use the polarization of light to orientate themselves. The ants determine their direction of travel in the interplay of the direction of the light waves, which varies with the time of day, and an internal biological clock. The desert ants (Cataglyphis fortis) can also perceive the distance they have traveled as the crow flies to the starting point (anthill).

Some other species also use ultrasound to orient themselves. To do this, they use stridulation (rubbing the rear pair of legs, which are equipped with small hairs or hooks, against the abdomen, cf. the chirping when barbecuing), sound waves from eight kilohertz up into the ultrasonic range. These are reflected on objects, collected with Johnston's organ and evaluated. Stridulation sounds can also arise from up and down movements of a gastric segment on an edge of the postpetiolus. For example, leaf cutter ants that have been buried can “call for help” and be heard and dug up by other members of their own species.

communication

The exchange of information in ants is mostly done chemically via various fragrances and tactilely by touching with the feelers. There are secretions for every situation, for example the alarm pheromones, such as the undecane from Dufour's glands. This olfactory communication is the ants' most important means of communication.

Any necessary information can also be passed on via antenna crosses. For example, the feelers touch each other briefly or long and abruptly or slidingly. This is called tactile communication. With this method, one ant can trick another ant to signal that it is hungry and needs goiter food. Even if one ant leads another to a food source and the scent trail is not yet sufficiently intense, this type of communication is necessary. These two ants organize the so-called tandem run. By touching the guests, the guided rear ant signals its presence. If this is no longer there, the guide waits and sprays secretions until both have found each other again.

Collective intelligence

If several ants transport prey to the nest together, this is not based on an agreement, i.e. on communicative intelligence. Rather, each ant tries to create the prey in the direction of the nest for itself. If enough ants have approached to be able to carry away the prey in bulk, and if enough ants are dragged in roughly the same direction, namely on the same road towards the nest, the transport train starts moving automatically. The better the road is marked by pheromones, the better the train will go.

In the case of the black garden ants, it has been proven that ants do not exclusively follow the pheromone trail (ant route) of the founder ant when they move their prey towards the nest. If a passage is so narrow that there is a collision between the ants moving back and forth, the ants returning home take an alternative route and create a practically parallel ant road that becomes more solid as a result of use. The reason why the returning ants evade is probably due to the fact that the ants can easily locate the nest using the built-in compass, even without a pheromone trace, which does not apply to the prey: this can only be found using the pheromone trace.

The ant species Cataulacus muticus provides an interesting example of collective intelligence. These ants live inside a species of bamboo. You can protect yourself against flooding when it rains in the following ways:

  1. The ants lock the trunk from the inside with their heads like a cork
  2. Any water that has penetrated is absorbed and excreted outside after the rain (coined term: “collective pee”).

Nest types

Most nests are made of small pieces of wood or plants, crumbs of earth, resin from conifers, or other natural materials. Different nest types can occur within one ant species.

Nomadic ant species, such as the wandering ants and driver ants, do not build nests. Since they are constantly on raids through the savannas of Africa or the rainforests of South America, they do not need permanent nesting sites. The queen and the brood are carried away from the front, which is up to 20 m wide. At night the workers form a living bivouac from their bodies around the queen and her brood. The ants hold onto the abdomen of another animal with their mandibles. In these bivouacs made up of thousands of bodies, the queen is better protected from all external influences than would be possible in any nest. They overcome obstacles by building a bridge out of their bodies over which the rest of the people can wander.

Earth nest

The earth nest is the most common type of nest in which at least the majority of all corridors and chambers are below the surface of the earth. Earth nests are very susceptible to the weather, so that they can usually only be found in particularly protected places such as under heat-storing stones. Some species also form a crater wall around their nest.

Most earth nests - such as that of the yellow meadow ant (Lasius flavus) - have a small dome. Such earth nests can absorb more sun rays than shallow nests.

Hill nest with scattered domes

The hilly nests with scattered domes offer better ventilation and, at the same time, better heat storage. These nests are usually built around rotten tree stumps that give them support. Most of the species of the genus Formica live in such hills. The upper layer of plant parts protects the nest from rain and cold; the lower layers are made of earth.

The corridors are laid out in such a way that water can run off them. In such nests, which can reach a height of two meters and a diameter of five meters and are as deep as they are high, there are numerous floors and galleries.

Such nests have to struggle with fungi due to their plant components, which is why the ants completely dig up the surface of the nest every one to two weeks. This can be observed very well if you spray some paint on it: after two weeks at the latest, it has completely disappeared and reappears in another place after four to six weeks. In winter, the upper part of the hill nests serves as frost protection, while all ants hibernate in the deeper chambers.

Wooden nest

Different species of ants cut nests and duct systems with their mandibles in rotten or hollow deadwood, as well as living trees, although the latter generally still have enough water and nutrient pipes to survive. The entrances are at the root ends, so that the nest cannot be seen from the outside of the trunk. The Central European black horse ant (Camponotus herculeanus) in particular gnaws pronounced nest chamber systems, so-called hanging gardens, into rotten trunks.

The glossy black wood ants (Lasius fuliginosus) are the only native representatives to build cardboard nests in trees. To do this, they chop up small wood and earth materials and soak this kneaded cardboard substance with honeydew that has been choked out of the goiter. This building material contains up to 50 percent sugar. Then they grow the fungus Cladosporium myrmecophilum, which gives stability to the nest walls through its hyphae (filamentous cell structure typical of mushrooms). Both living beings live in symbiosis, because the fungus finds optimal food sources in this way.

Cardboard nests

Cardboard nests are mainly found in tropical ants, which usually build them freely hanging.

Silk nests

Weaver ants of the genus Oecophylla build their nests using a silk secretion from their larvae, with which tufts of leaves are spun together. Most of the time these nests are also free-hanging. Others build their nests exclusively from silk, which they cover or camouflage with dead organic material (detritus).

Ant plants

Ant plants or myrmecophytes include all those plants that ants need for food (for example as elaiosome-producing plants) for reproduction or as permanent living space (domatia).

Domatia are plants with cavities in which ants nest (myrmecophylaxis). The species of the tropical genus Tetraponera (Pseudomyrmecinae) and the Malaysian Cataulacus muticus (Myrmicinae) live in the hollow stems of two giant bamboo species. Some ants breed aphids in the plants, such as the species of the genus Azteca, which live in hollow branches and trunks of the plants of the genus Cecropia divided by transverse walls.

Other plants in which ants live are those of the genus Myrmecodia, or a buffalo horn acacia of the species Acacia sphaerocephala, in whose hollow thorns the ants nest.

Other nesting options

The smaller species, especially the leptothorax, do not require larger territories. These use small knotholes from various larvae or live in snail shells or acorns.

Interaction with other living beings

Predators

Some ant lion species catch ants with the help of funnels, which they hollow in sandy soil.

In Central Europe, some species of birds such as B. the green, great spotted and black woodpecker, small snakes, amphibians, spiders, insects but also wild boars of ants. The ant maid larvae, the ant lions, specialize in capturing ants, among other things. The green woodpecker covers half of its daily food requirements with around 3000 to 5000 ants.

Outside Europe, anteaters are especially important predators, in the south of the USA and in Central America, the toad lizards (phrynosoma) are of greater importance in this respect, as they feed almost exclusively on ants.

Many invertebrates (such as predatory bugs) imitate the ants' pheromones and use them to lay ant trails on which the ants run towards their enemies. Some arachnids, species of millipedes, and beetles specifically mimic the pheromones found in ant larvae. In this way, they can enter the burrow to the brood chambers and use the larvae unhindered, sometimes also carried by the brood keepers. Both forms can be counted among the chemical mimicry.

Ant guests

Ant guests are animals that live in ant burrows. This includes mainly insects, but also spiders. Forms of coexistence are synechthria or syllestium, synökie and symphyly.

In the predatory form - synechthria or syllestium - the ant guest feeds on ants, ant larvae or ant eggs. Various strategies are used: Ant spiders mimic ants in shape and behavior, while some blue caterpillars, for example, protect themselves against attacks by ants with a thick protective coat.

Synökie describes the coexistence of different species without any particular mutual influence. Various springtail species, the larvae of the hoverfly genus Microdon, the leaf beetle genus Clytra, crickets of the genus Myrmecophila (e.g. the ant cricket), antfish (Atelura spec.) And the rophies of the genus Dinarda live on the food supplies of the ants. Rose beetle larvae are often found outside the ant burrows.

With the symphylie, the ant guests are protected and often fed. For example, the ants receive nutritious glandular secretions. Such guests include the rophies of the genera Lomechusa and Atemeles, club beetles of the genus Claviger and some blue caterpillars.

75 percent of the bluish species occurring worldwide (a family of butterflies) live myrmekophil, i.e. from or with ants. Thereby symbiosis and parasitism occur with all intermediate stages. Some caterpillars, such as the silver-green blue-green (Polyommatus coridon) or the blue-cranesbill (Plebeius eumedon) serve the ants as sources of honeydew, similar to the plant lice. For this they are protected from predators. Other blue caterpillars live parasitically or symbiotically as ant guests in the ant burrow. The caterpillar of the blue gentian ant is adopted by ants of the species Myrmica ruginodis and fed like an ant larva for no consideration. The caterpillar of the dark blue ants is cared for by the red garden ant (Myrmica rubra) like the brood, but it gives off sugar water to the ants. In addition, the caterpillar eats the brood of ants.

Some bluebirds are totally dependent on a specific species of ants. The common blue ant needs knot ants of the species Myrmica sabuleti to develop. Against the secretion of a sugary secretion, the caterpillar is allowed to feed on ant larvae. A decline in the ants due to changes in the livestock industry in the British Isles (the ants prefer short, i.e. grazed, grass) led to the extinction of the bluer there.

Parasites

Ants can be infested with hemolymph sucking mites. There are also mites of the genus Antennophorus: They live on the ants and stimulate the ants to release drops of food on which the mites feed. Mites of the species Laelops oophilus live with the larvae and are fed by the brood keepers.

The internal parasites include the larvae of some parasitic wasps and various nematodes. Ants also serve as a second intermediate host for the little liver fluke.

Ant and human

Economical meaning

Considered wood pests, the harvest ants of the species Pogonomyrmex barbatus can promote forestry by accelerating the breakdown and conversion of wood that is already infested by other insects. While the many seed-collecting ants can be detrimental to agriculture if they become too numerous in the vicinity of cornfields and granaries, their presence can normally promote production by counteracting the increase in harmful parasitic beetles. Aphid ants are common pests in gardens. Other important contributions to forestry in tropical and subtropical areas are probably made by the predatory driver ants or wandering ants. They are effective in eliminating other, even more harmful, insects and so are not always unwelcome in human habitat.

Dangers to humans

The red fire ants were introduced to Australia in the early 1950s. Under the very favorable environmental conditions of the Australian outback, they have multiplied strongly, including: also near cities.

In fact, they see people as intruders into their territory and try to defend themselves. In some people, their bites and the poison from their sting cause allergies like bee or wasp stings.

attitude

Native or exotic species of ants can be kept in special, prefabricated containers, the so-called formicariums.

Ant keeping has now become a popular hobby; it belongs to the field of knowledge of terraristics. The necessary purchases depend on the requirements of the respective species. For example, the effort for the leaf cutter ants Atta cephalotes is unusually high, as they need a constant supply of fresh leaves in order to be able to grow their food (a fungus). Native species, such as the black garden ant (Lasius niger), on the other hand, can also be kept in a simple plaster nest with an attached arena (sandy soil).

For European species, it is important to observe the hibernation period from mid-October to April, which should either be kept in suitable containers in the refrigerator or protected from frost on the balcony or in the garden. Without this hibernation there is a weakening of the ant colony, which can lead to the death of the colony.

Source: de.wikipedia.org | Ants