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How do ants spontaneously grow wings?

How do ants spontaneously grow wings?



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On hot summer nights we get flocks of ants that have grown wings (from what I know to migrate nests).

It appears the wings are not permanent, but are grown for a temporary purpose.

From what I know these events are triggered by climatic conditions (warm evenings).

In other species, wings seem like a really big deal and are grown from birth - wheras ants seem to just grow them 'on the spur of the moment'.

My question is How do ants spontaneously grow wings? Are they a spare layer of skin that is normally discarded and only comes into action when necessary?


See the Wikipedia entry for nuptual flight.

The ants that you see most often are (wingless) female workers. The winged ants that you see are male drones whose only role is to fly with young queens for mating. The drones follow a different developmental pathway, emerge from the pupa as winged ants, and then wait in the nest until conditions are right for the big event.


Six amazing facts you need to know about ants

Charlie Durant receives funding from the Biotechnology and Biological Sciences Research Council (BBSRC).

Max John receives funding from the Biotechnology and Biological Sciences Research Council (BBSRC), and the Genetics Society.

Rob Hammond receives funding from NERC, BBSRC, The Genetics Society.

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University of Leicester provides funding as a member of The Conversation UK.

The Conversation UK receives funding from these organisations

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Have you have seen ants this year? In Britain, they were probably black garden ants, known as Lasius niger – Europe’s most common ant. One of somewhere between 12,000 and 20,000 species, they are the scourge of gardeners – but also fascinating.

The small, black, wingless workers run around the pavements, crawl up your plants tending aphids or collect tasty morsels from your kitchen. And the flying ants that occasionally appear on a warm summer’s evening are actually the reproductive siblings of these non-winged workers. Here’s what else you need to know:


Why Do Ants Have Wings?

Looking at winged ants can be a bit startling for a lot of us. After all, ants are supposed to be crawling on the ground not to be flying around. Or are they?

Flying ants are actually quite a normal thing in the ant world as they are a part of the standard ant life cycle. Almost all ant species have winged members and only very few don’t. Ants with wings aren’t more “dangerous” than other ants in any way but they do signify the further spreading of ant colonies. So, whether you encounter black ants with wings or flying red ants, here’s we’ll explain what that indicates.

Why do ants have wings?

Certain members of an ant colony are born with wings and take flight about once per year – usually in the spring or the summer, depending on the species. As the Society of Biology points out, for example, black garden ants tend to do this in July or August.

Cristina Romero Palma/Shutterstock.com

The reason ants do this is to spread to new locations and start colonies there. The winged members of an ant colony are female queen ants and male “drone” ants. The former fly as far as they can to seek suitable nesting locations and start attracting males for mating there. The male drones themselves also try to fly as far away as they can to avoid mixing with similar genetic materials and when they hear the call of a female queen – they go to do their job.

Once a male drone delivers his genetic material to an available queen ant he will die shortly – within days or several weeks at most. Male drone ants have the shortest lifespan of all ant types as breeding is their only purpose in life. They are also much more numerous than females so when you encounter a winged ant on a window or somewhere else than it most probably is either a male searching for a queen to mate with or a male that’s already done his job and is “retired”.

If the winged ant you notice is significantly larger, then it is probably a queen. If you happen to encounter it in your home or on your property and you don’t want an ant colony to sprout there a week after, killing said queen might be a good idea. However, more often than not, the winged ants you encounter will be harmless males.

Do all ants have wings?

The vast majority of an ant colony are wingless workers. All worker ants are technically female but neither of them is a queen ant, neither of them is capable of reproducing, and neither of them has had or will have wings.

There are also several species of ants that don’t have any winged members at all. Instead, these ants reproduce by “budding”. Essentially, both the female ant queens and the male drones crawl to new nest locations instead of flying there. This is a much less effective strategy, however, as it’s slower, it limits the distance these ants can cover before they mate and/or die, and it also leaves them even more exposed to predators.

Even flying ants are quite vulnerable to predators, however. The reason such high numbers of male drones and female queens are released from each nest every year is precisely because the majority of them will either be killed and eaten by birds and dragonflies or will simply starve to death before they manage to mate. Only a few make it but once they do, the queens are fast to start reproducing. Once they start nesting, the queens will shed their wings and never fly again.

How to tell the difference between winged ants and termites?

One annoying part of the fact that some ants fly is that it makes them hard to distinguish from termites. As termites are one of most maligned house pests, many homeowners have learned the hard way to be extra cautious every time they see a winged ant-like insect around their property.

Ants themselves can be harmful to our homes as carpenter ants, like termites, tend to chew wood and dig tunnels through our homes’ walls and foundations. There are quite a bit of difference between termites, carpenter ants, and regular ants, however, and as annoying as carpenter ants are, they are much easier to deal with than termites.

So, what are the differences between carpenter ants with wings and termites?

For one, termites are actually members of the cockroach family. In fact, carpenter ants are known to prey on termites, so at the very least the two species of pests are at war with each other.

In terms of appearances, they can look quite similar, however. Both winged carpenter ants and termites have a similar body size and both insects have long wings. They are distinguishable nonetheless, however, so here are a few pointers:


Ants regulate growth of seemingly 'useless' organ to make huge soldiers

The variation in the size of soldiers and minor workers is caused by the brief presence, during the larval phase of a seemingly 'useless' rudimentary organ. This discovery answers a question -- about the difference in ants in a single colony -- that it lead Charles Darwin to doubt his own theory of evolution. Credit: Alex Wild

Scientists at McGill have found the answer to a question that perplexed Charles Darwin. So much so, that it actually led him to doubt his own theory of evolution. He wondered, if natural selection works at the level of the individual, fighting for survival and reproduction, how can a single colony produce worker ants that are so dramatically different in size—from the "minor" workers with their small heads and bodies, to the large-headed soldiers with their huge mandibles—especially if, as in the genus Pheidole, they are sterile? The answer, according to a paper published today in Nature, is that the colony itself generates soldiers and regulates the balance between soldiers and "minor" workers thanks to a seemingly unimportant rudimentary "organ" which appears only briefly during the final stages of larval development. And only in some of the ants—the ones that will become soldiers.

"It was a completely unexpected finding. People had noticed that during the development of soldiers that a seemingly useless rudimentary "organ" would pop up and then disappear. But they assumed that it was just a secondary effect of the hormones and nutrition that were responsible for turning the larvae into soldiers," says Ehab Abouheif from McGill's Biology Department, the senior author on the paper.

Rajendhran Rajakumar the first author adds, "What we discovered was that these rudimentary "organs" are not a secondary effect of hormones and nutrition, but are instead responsible for generating the soldiers. It is their passing presence that regulates the head and body of soldiers to grow at rapid rates, until you get these big-headed soldiers with huge mandibles and big bodies."

Now you see it, now you don't

Abouheif has been studying wings in ants for the past twenty-three years. He was curious about the function of the wing imaginal disc which appear, transiently, in the final stages of larval development among the soldier ants. Even though the soldier ants never actually develop wings. So he and his team, spent nine years in the lab, using various techniques (surgical and molecular) to cut away portions of the rudimentary wing discs from the larvae of soldier ants in the widespread and very diverse Pheidole genus. They discovered that by doing so, they affected the growth of the head and the body. Indeed, they found that they were able to scale the size of soldier ants by cutting away differing degrees of the imaginal wing discs, with a corresponding decrease in the size of the heads and bodies of the soldier ants. It was clear confirmation that the rudimentary wing discs play a crucial role in the development of soldier ants.

Ehab Abouheif, a McGill biologist has been studying ants for close to 25 years. His interested in ant evolution was prompted by reading Charles Darwin's The Origin of the Species, where he describes how perplexed he felt about the great variety in the sizes of worker ants in a single colony -- from the large-headed "soldier" ants to the small-bodied "minor" workers. Credit: Neale McDevitt

Soldier ants keep the colony in balance

The researchers also discovered that the colony as a whole maintains the balance between soldiers and minor workers by regulating the growth of the rudimentary wing discs in larvae. Earlier research had shown that the ratio of "minor" workers to soldiers remains constant in all colonies of the Pheidole genus, with a proportion of "minor" workers at 90-95 % to 5-10% soldiers. The McGill team has found that the soldier ants maintain this ratio by halting the growth of the rudimentary wing disc with an inhibitory pheromone when there are too many soldiers. However, the colony is able to ramp up the number of soldier ants very quickly if it is under threat or the numbers of soldiers have dropped for some reason, because the rudimentary wing discs that play such a crucial role in regulating the number of soldier ants appear only in the final stages of larval development.

A more important role for all rudimentary organs than previously suspected?

Based on his teams' discovery in ants, Abouheif proposes that rudimentary organs may play a much larger role in an organism's development than had previously been imagined. "Until now, people have assumed that these organs simply offer evidence of evolution and common descent, overlooking any current functions for them. Now that we know the crucial role played in Pheidole ant colonies by the rudimentary wing disc, it means that we will have to go back and look at other rudimentary organs in the same light. Who knows what scientists will discover?"

Useful ant facts. Credit: McGill University

Ant Biology

Ants are fascinating creatures. They have been here for millions of years and can be traced as far back to the age of the dinosaurs in the Mesozoic Era! There are over 15,000 described species of ants and we are discovering new species around the world all the time! The following are our most commonly asked ant questions regarding ant biology. Be sure to also check out at our store the AntsCanada Ultimate Ant Keeping Handbook™ E-Book with information on ant biology, ecology, and evolution.

What is the scientific name of an ant?
Actually, an ant is not a single species. Ants are in fact a family of thousands and thousands of different species. The family of ants is Formicidae under the order known as Hymenoptera, which also includes wasps and bees.

What is the scientific study of ants?
Myrmecology is the scientific study of ants. A myrmecologist is a person who studies ants, however most myrmecologists simply refer to themselves as entomologists or biologists because working with ants often necessitates work with and knowledge of other flora and fauna ants are so closely tied to all the living things around them.

What are the life stages of an ant?
Ants, like many insects, undergo a process called complete metamorphosis, where they start off as an egg, then hatch into a larva, which then becomes a pupa, out of which emerges an adult ant.

What is the life cycle of an ant?
The ant life cycle is a little more complicated because ants have special forms of ant known as alates, or reproductive ants. These alates appear in the colony from special eggs laid by the queen usually when the colony passes a certain size. These alates are larger than the worker ants and are born with wings. They are the reproductive males and young queens. During what is called a nuptial flight, which takes place at a specific time of the year, all these alates take to the air and mate with each other, after which the male alates die and the female alates drop to the ground, break off their wings, and venture off on their own in search of a suitable place to start their new colony alone. These now wingless queens become the official egg-laying queen of their new colony. Eventually, when the new colony gets big enough, the queen will begin to lay eggs which will turn into alates, and the process starts all over again.

How long does it take for an ant to develop from egg to worker?
It depends on the species of ant and factors like warmth and temperature. A queen with new eggs that are kept a few degrees above room temperature develop faster. For most species it takes about 3-5 weeks, but for some ants like those belonging to Camponotus take two months to get from from egg to worker.

After a newly mated queen settles into her claustral chamber (or test tube) how long does it take for her to lay eggs?
In most cases, it takes a queen anywhere between a few hours to a week to lay eggs. Some queens, especially those caught prior to winter, i.e. hibernation season, may hold off laying eggs until after hibernation. These queen ants will start laying eggs by Spring.

What is the ant caste system (queens/males/workers/majors/minors)?
Ants are social insects that have a caste system of different specialized forms that take on various unique functions. All ants are born into their respective caste and remain in that form for their entire life. There are worker ants, which most people see wandering around above ground. They handle the bulk of the colony’s duties, including cleaning, food collection, tunnel digging, caring for the young, defense, and more. They are all female and are barren. There are also female alates, which are young virgin queens born in the nest and have wings. These become the new founding queens of their own colonies after they mate during a nuptial flight. There are also male ants, which tend to look more like wasps but are typically smaller than the queen alates. Their only job is to mate with the female alates during nuptial flight, after which they die. There are also other denominations of workers in some species, e.g.majors which are specialized larger worker ants often used to defend the colony from attack or tear apart food items, and minors which are smaller worker ants often used for caring for the young. Some highly specialized species of ants even have additional worker denominations like submajors (smaller majors).

How do ants communicate?
Ants have a chemical language. They communicate through pheromones. There is a different pheromone for every message an ant might want to deliver to other ants. These pheromones are expelled from glands at various areas of the body. Ants also can create sounds by rapidly rubbing body parts together (a process called stridulation) or in some species drumming on the ground with their head and legs, which causes vibrations which other nearby ants can perceive. Vibrational communication in ants usually involves an attempt to excite or alarm fellow ants.

Can ants see well?
Some ant species like Weaver Ants (species: Oecophylla smaragdina) have very good vision. Others have poor vision and are thought to only see shapes and light. Some subterrestrial ant species that never come to the surface have no functioning eyes at all. Perhaps the most used senses of an ant are the senses of smell, touch, and taste all through the antennae. Ants do not have ears.

How do ants breathe?
Ants breathe through spiracles small openings in their gaster (rear portion of the ant).

What are the body parts of an ant?
Watch this video (and make sure annotations are ON!).

How long do ants live?
The life expectancy varies with the species. Queens usually live the longest. Some species like Myrmica rubra are thought to live only two or three years while other species like some from the genus Formica, can live for 15 years. The record for ant longevity is held by a queen of Lasius niger who, in a German laboratory nest, lived for 29 years. Worker ants usually live for a several weeks to months, while male ants typically survive for a single season.


How do Ants Reproduce?

Ants are one of the most abundant insects on our planet and the reasons are their eusocial, complex societal behaviors and their ability to survive in many and various ecosystems. Like most other animal societies, reproduction is one of the core reasons why ants are so prevalent.

Reproduction for ants is a complex phenomenon that involves finding, selecting and successfully fertilizing females to ensure that the eggs laid are able to survive and molt through the successive stages of the ant’s life cycle – larvae, pupae and adults.

Ant Life Cycle

A brief description of the respective stages within the ant’s life cycle may be helpful when describing how ants reproduce. The eggs are small and cream colored and tended to by the workers.

Ant larvae have no legs and are grub-like in appearance. Pupae are somewhat the same in appearance as adult worker ants and are initially cream colored, but become darker before becoming adult ants.

The adult stages are the older ants we typically see foraging for food or protecting the colony from intruders, while the nurse ant adults are younger workers that attend to the needs of the queen and the eggs, larvae and pupae. The colony queen ants are almost always bigger than other members of their colony.

Ant Swarms

Each ant colony begins with, and centers upon, the queen, whose sole purpose is to reproduce. This reproductive behavior begins with winged males and virgin winged queens leaving the existing nest and swarming to search for a mate from another colony.

The males and females within the swarm are called alates and their wings allow them to disperse away from the “mother” colony, so the likelihood is greater that no inbreeding with their relatives occurs.

Starting a New Colony

Once mated, the queen never mates again. Instead of repetitive mating, she stores the male’s sperm in a specialized pouch until such time as she opens the pouch and allows sperm to fertilize the eggs she produces.

After mating, queen ants and male ants lose their wings. The queen scurries off in search of a site to start her new nest. If she survives, she digs a nest, lays eggs, and single-handedly raises her first brood that consists entirely of workers. After mating, the male generally lives a short life in isolation.

The nest’s queen controls the gender and function of her offspring since her fertilized eggs become either wingless female workers or reproductively capable virgin queens.

Unfertilized eggs develop into winged males who do no work other than to fertilize a virgin queen. The queen produces myriads of workers by secreting a chemical that retards wing growth and ovary development in the female larvae. Virgin queens are produced only when there are sufficient workers to allow for the expansion of the colony.

Worker Ants

The workers enlarge the nest, excavate elaborate tunnel systems, and transport new eggs into special hatching chambers. Hatchling larvae are fed and cleaned, and pupated larvae in cocoons are protected until the young adults emerge to become workers themselves. At this point the colony’s workers are mostly directed to expansion of the colony and caring for the queen.

Depending upon the ant species, it may take from one to several years for a colony to become large enough for the queen to begin producing virgin queens and males that will leave the colony, swarm, mate and begin a new colony in another location. This process and behavior is typical of most ant colonies.

Multiple Queens

However, some ant species reproduce and develop new colonies with several queens who work together. Sometimes, groups of workers swarm from the nest with a young queen to help her establish her new nest.

In colonies with several already fertile queens, an entire group of ants will break away along with their with their individual queens to establish individual colonies. In single queen colonies, such as those of some fire ants, the death of the queen means the death of the colony, as she leaves no successors.

Colony Budding

Colonies with multiple queens may also reproduce by a process called colony budding. Ants that reproduce by budding do not have mating swarms. Budding occurs when one or more fertile queens and a group of workers leave an established nest and move to a new nest site.

The respective roles of queen and workers remain the same in the budded colony since the workers assist in the establishment and care of the new, budded colony. Pharaoh ants, some fire ants, ghost ants and Argentine ants, some of the most difficult ant species to control, spread by budding.

Interestingly, Pharaoh ant workers by themselves can form a successful budded colony by developing and caring for the queens that are produced from the ant brood they brought along with them.


Contents

The word ant and its chiefly dialectal form emmet [5] come from ante, emete of Middle English, which come from ǣmette of Old English, and these are all related to the dialectal Dutch emt and the Old High German āmeiza, from which comes the modern German Ameise. All of these words come from West Germanic *ǣmaitjōn, and the original meaning of the word was "the biter" (from Proto-Germanic *ai-, "off, away" + *mait- "cut"). [6] [7] The family name Formicidae is derived from the Latin formīca ("ant") [8] from which the words in other Romance languages, such as the Portuguese formiga, Italian formica, Spanish hormiga, Romanian furnică, and French fourmi are derived. It has been hypothesised that a Proto-Indo-European word *morwi- was used, cf. Sanskrit vamrah, Greek μύρμηξ mýrmēx, Old Church Slavonic mraviji, Old Irish moirb, Old Norse maurr, Dutch mier, Swedish myra, Danish myre, Middle Dutch miere, Crimean Gothic miera. [9] [10]

The family Formicidae belongs to the order Hymenoptera, which also includes sawflies, bees, and wasps. Ants evolved from a lineage within the stinging wasps, and a 2013 study suggests that they are a sister group of the Apoidea. [11] In 1966, E. O. Wilson and his colleagues identified the fossil remains of an ant (Sphecomyrma) that lived in the Cretaceous period. The specimen, trapped in amber dating back to around 92 million years ago, has features found in some wasps, but not found in modern ants. [12] Sphecomyrma was possibly a ground forager, while Haidomyrmex and Haidomyrmodes, related genera in subfamily Sphecomyrminae, are reconstructed as active arboreal predators. [13] Older ants in the genus Sphecomyrmodes have been found in 99 million year-old amber from Myanmar. [14] [15] A 2006 study suggested that ants arose tens of millions of years earlier than previously thought, up to 168 million years ago. [1] After the rise of flowering plants about 100 million years ago they diversified and assumed ecological dominance around 60 million years ago. [16] [1] [17] [18] Some groups, such as the Leptanillinae and Martialinae, are suggested to have diversified from early primitive ants that were likely to have been predators underneath the surface of the soil. [3] [19]

During the Cretaceous period, a few species of primitive ants ranged widely on the Laurasian supercontinent (the Northern Hemisphere). They were scarce in comparison to the populations of other insects, representing only about 1% of the entire insect population. Ants became dominant after adaptive radiation at the beginning of the Paleogene period. By the Oligocene and Miocene, ants had come to represent 20–40% of all insects found in major fossil deposits. Of the species that lived in the Eocene epoch, around one in 10 genera survive to the present. Genera surviving today comprise 56% of the genera in Baltic amber fossils (early Oligocene), and 92% of the genera in Dominican amber fossils (apparently early Miocene). [16] [20]

Termites live in colonies and are sometimes called ‘white ants’, but termites are not ants. They are the sub-order Isoptera, and together with cockroaches they form the order Blattodea. Blattodeans are related to mantids, crickets, and other winged insects that do not undergo full metamorphosis. Like ants, termites are eusocial, with sterile workers, but they differ greatly in the genetics of reproduction. The similarity of their social structure to that of ants is attributed to convergent evolution. [21] Velvet ants look like large ants, but are wingless female wasps. [22] [23]

Ants are found on all continents except Antarctica, and only a few large islands, such as Greenland, Iceland, parts of Polynesia and the Hawaiian Islands lack native ant species. [25] [26] Ants occupy a wide range of ecological niches and exploit many different food resources as direct or indirect herbivores, predators and scavengers. Most ant species are omnivorous generalists, but a few are specialist feeders. Their ecological dominance is demonstrated by their biomass: ants are estimated to contribute 15–20 % (on average and nearly 25% in the tropics) of terrestrial animal biomass, exceeding that of the vertebrates. [27]

Ants range in size from 0.75 to 52 millimetres (0.030–2.0 in), [28] [29] the largest species being the fossil Titanomyrma giganteum, the queen of which was 6 centimetres (2.4 in) long with a wingspan of 15 centimetres (5.9 in). [30] Ants vary in colour most ants are red or black, but a few species are green and some tropical species have a metallic lustre. More than 13,800 species are currently known [31] (with upper estimates of the potential existence of about 22,000 see the article List of ant genera), with the greatest diversity in the tropics. Taxonomic studies continue to resolve the classification and systematics of ants. Online databases of ant species, including AntWeb and the Hymenoptera Name Server, help to keep track of the known and newly described species. [31] The relative ease with which ants may be sampled and studied in ecosystems has made them useful as indicator species in biodiversity studies. [32] [33]

Ants are distinct in their morphology from other insects in having geniculate (elbowed) antennae, metapleural glands, and a strong constriction of their second abdominal segment into a node-like petiole. The head, mesosoma, and metasoma are the three distinct body segments (formally tagmata). The petiole forms a narrow waist between their mesosoma (thorax plus the first abdominal segment, which is fused to it) and gaster (abdomen less the abdominal segments in the petiole). The petiole may be formed by one or two nodes (the second alone, or the second and third abdominal segments). [34]

Like other insects, ants have an exoskeleton, an external covering that provides a protective casing around the body and a point of attachment for muscles, in contrast to the internal skeletons of humans and other vertebrates. Insects do not have lungs oxygen and other gases, such as carbon dioxide, pass through their exoskeleton via tiny valves called spiracles. Insects also lack closed blood vessels instead, they have a long, thin, perforated tube along the top of the body (called the "dorsal aorta") that functions like a heart, and pumps haemolymph toward the head, thus driving the circulation of the internal fluids. The nervous system consists of a ventral nerve cord that runs the length of the body, with several ganglia and branches along the way reaching into the extremities of the appendages. [35]

An ant's head contains many sensory organs. Like most insects, ants have compound eyes made from numerous tiny lenses attached together. Ant eyes are good for acute movement detection, but do not offer a high resolution image. They also have three small ocelli (simple eyes) on the top of the head that detect light levels and polarization. [36] Compared to vertebrates, ants tend to have blurrier eyesight, particularly in smaller species, [37] and a few subterranean taxa are completely blind. [2] However, some ants, such as Australia's bulldog ant, have excellent vision and are capable of discriminating the distance and size of objects moving nearly a metre away. [38]

Two antennae ("feelers") are attached to the head these organs detect chemicals, air currents, and vibrations they also are used to transmit and receive signals through touch. The head has two strong jaws, the mandibles, used to carry food, manipulate objects, construct nests, and for defence. [35] In some species, a small pocket (infrabuccal chamber) inside the mouth stores food, so it may be passed to other ants or their larvae. [39]

Mesosoma

Both the legs and wings of the ant are attached to the mesosoma ("thorax"). The legs terminate in a hooked claw which allows them to hook on and climb surfaces. [40] Only reproductive ants- queens, and males, have wings. Queens shed their wings after the nuptial flight, leaving visible stubs, a distinguishing feature of queens. In a few species, wingless queens (ergatoids) and males occur. [35]

Metasoma

The metasoma (the "abdomen") of the ant houses important internal organs, including those of the reproductive, respiratory (tracheae), and excretory systems. Workers of many species have their egg-laying structures modified into stings that are used for subduing prey and defending their nests. [35]

Polymorphism

In the colonies of a few ant species, there are physical castes—workers in distinct size-classes, called minor, median, and major ergates. Often, the larger ants have disproportionately larger heads, and correspondingly stronger mandibles. These are known as macrergates while smaller workers are known as micrergates. [41] Although formally known as dinergates, such individuals are sometimes called "soldier" ants because their stronger mandibles make them more effective in fighting, although they still are workers and their "duties" typically do not vary greatly from the minor or median workers. In a few species, the median workers are absent, creating a sharp divide between the minors and majors. [42] Weaver ants, for example, have a distinct bimodal size distribution. [43] [44] Some other species show continuous variation in the size of workers. The smallest and largest workers in Pheidologeton diversus show nearly a 500-fold difference in their dry-weights. [45]

Workers cannot mate however, because of the haplodiploid sex-determination system in ants, workers of a number of species can lay unfertilised eggs that become fully fertile, haploid males. The role of workers may change with their age and in some species, such as honeypot ants, young workers are fed until their gasters are distended, and act as living food storage vessels. These food storage workers are called repletes. [46] For instance, these replete workers develop in the North American honeypot ant Myrmecocystus mexicanus. Usually the largest workers in the colony develop into repletes and, if repletes are removed from the colony, other workers become repletes, demonstrating the flexibility of this particular polymorphism. [47] This polymorphism in morphology and behaviour of workers initially was thought to be determined by environmental factors such as nutrition and hormones that led to different developmental paths however, genetic differences between worker castes have been noted in Acromyrmex sp. [48] These polymorphisms are caused by relatively small genetic changes differences in a single gene of Solenopsis invicta can decide whether the colony will have single or multiple queens. [49] The Australian jack jumper ant (Myrmecia pilosula) has only a single pair of chromosomes (with the males having just one chromosome as they are haploid), the lowest number known for any animal, making it an interesting subject for studies in the genetics and developmental biology of social insects. [50] [51]

The life of an ant starts from an egg if the egg is fertilised, the progeny will be female diploid, if not, it will be male haploid. Ants develop by complete metamorphosis with the larva stages passing through a pupal stage before emerging as an adult. The larva is largely immobile and is fed and cared for by workers. Food is given to the larvae by trophallaxis, a process in which an ant regurgitates liquid food held in its crop. This is also how adults share food, stored in the "social stomach". Larvae, especially in the later stages, may also be provided solid food, such as trophic eggs, pieces of prey, and seeds brought by workers. [52]

The larvae grow through a series of four or five moults and enter the pupal stage. The pupa has the appendages free and not fused to the body as in a butterfly pupa. [53] The differentiation into queens and workers (which are both female), and different castes of workers, is influenced in some species by the nutrition the larvae obtain. Genetic influences and the control of gene expression by the developmental environment are complex and the determination of caste continues to be a subject of research. [54] Winged male ants, called drones (termed "aner" in old literature [55] ), emerge from pupae along with the usually winged breeding females. Some species, such as army ants, have wingless queens. Larvae and pupae need to be kept at fairly constant temperatures to ensure proper development, and so often are moved around among the various brood chambers within the colony. [56]

A new ergate spends the first few days of its adult life caring for the queen and young. She then graduates to digging and other nest work, and later to defending the nest and foraging. These changes are sometimes fairly sudden, and define what are called temporal castes. An explanation for the sequence is suggested by the high casualties involved in foraging, making it an acceptable risk only for ants who are older and are likely to die soon of natural causes. [57] [58]

Ant colonies can be long-lived. The queens can live for up to 30 years, and workers live from 1 to 3 years. Males, however, are more transitory, being quite short-lived and surviving for only a few weeks. [59] Ant queens are estimated to live 100 times as long as solitary insects of a similar size. [60]

Ants are active all year long in the tropics, but, in cooler regions, they survive the winter in a state of dormancy known as hibernation. The forms of inactivity are varied and some temperate species have larvae going into the inactive state (diapause), while in others, the adults alone pass the winter in a state of reduced activity. [61]

Reproduction

A wide range of reproductive strategies have been noted in ant species. Females of many species are known to be capable of reproducing asexually through thelytokous parthenogenesis. [62] Secretions from the male accessory glands in some species can plug the female genital opening and prevent females from re-mating. [63] Most ant species have a system in which only the queen and breeding females have the ability to mate. Contrary to popular belief, some ant nests have multiple queens, while others may exist without queens. Workers with the ability to reproduce are called "gamergates" and colonies that lack queens are then called gamergate colonies colonies with queens are said to be queen-right. [64]

Drones can also mate with existing queens by entering a foreign colony, such as in army ants. When the drone is initially attacked by the workers, it releases a mating pheromone. If recognized as a mate, it will be carried to the queen to mate. [65] Males may also patrol the nest and fight others by grabbing them with their mandibles, piercing their exoskeleton and then marking them with a pheromone. The marked male is interpreted as an invader by worker ants and is killed. [66]

Most ants are univoltine, producing a new generation each year. [67] During the species-specific breeding period, winged females and winged males, known to entomologists as alates, leave the colony in what is called a nuptial flight. The nuptial flight usually takes place in the late spring or early summer when the weather is hot and humid. Heat makes flying easier and freshly fallen rain makes the ground softer for mated queens to dig nests. [68] Males typically take flight before the females. Males then use visual cues to find a common mating ground, for example, a landmark such as a pine tree to which other males in the area converge. Males secrete a mating pheromone that females follow. Males will mount females in the air, but the actual mating process usually takes place on the ground. Females of some species mate with just one male but in others they may mate with as many as ten or more different males, storing the sperm in their spermathecae. [69] In Cardiocondyla elegans, workers may transport newly emerged queens to other conspecific nests where wingless males from unrelated colonies can mate with them, a behavioural adaptation that may reduce the chances of inbreeding. [70]

Mated females then seek a suitable place to begin a colony. There, they break off their wings using their tibial spurs and begin to lay and care for eggs. The females can selectively fertilise future eggs with the sperm stored to produce diploid workers or lay unfertilized haploid eggs to produce drones. The first workers to hatch are known as nanitics, [71] and are weaker and smaller than later workers, but they begin to serve the colony immediately. They enlarge the nest, forage for food, and care for the other eggs. Species that have multiple queens may have a queen leaving the nest along with some workers to found a colony at a new site, [69] a process akin to swarming in honeybees.

Communication

Ants communicate with each other using pheromones, sounds, and touch. [72] The use of pheromones as chemical signals is more developed in ants, such as the red harvester ant, than in other hymenopteran groups. Like other insects, ants perceive smells with their long, thin, and mobile antennae. The paired antennae provide information about the direction and intensity of scents. Since most ants live on the ground, they use the soil surface to leave pheromone trails that may be followed by other ants. In species that forage in groups, a forager that finds food marks a trail on the way back to the colony this trail is followed by other ants, these ants then reinforce the trail when they head back with food to the colony. When the food source is exhausted, no new trails are marked by returning ants and the scent slowly dissipates. This behaviour helps ants deal with changes in their environment. For instance, when an established path to a food source is blocked by an obstacle, the foragers leave the path to explore new routes. If an ant is successful, it leaves a new trail marking the shortest route on its return. Successful trails are followed by more ants, reinforcing better routes and gradually identifying the best path. [73]

Ants use pheromones for more than just making trails. A crushed ant emits an alarm pheromone that sends nearby ants into an attack frenzy and attracts more ants from farther away. Several ant species even use "propaganda pheromones" to confuse enemy ants and make them fight among themselves. [74] Pheromones are produced by a wide range of structures including Dufour's glands, poison glands and glands on the hindgut, pygidium, rectum, sternum, and hind tibia. [60] Pheromones also are exchanged, mixed with food, and passed by trophallaxis, transferring information within the colony. [75] This allows other ants to detect what task group (e.g., foraging or nest maintenance) other colony members belong to. [76] In ant species with queen castes, when the dominant queen stops producing a specific pheromone, workers begin to raise new queens in the colony. [77]

Some ants produce sounds by stridulation, using the gaster segments and their mandibles. Sounds may be used to communicate with colony members or with other species. [78] [79]

Defence

Ants attack and defend themselves by biting and, in many species, by stinging, often injecting or spraying chemicals, such as formic acid in the case of formicine ants, alkaloids and piperidines in fire ants, and a variety of protein components in other ants. Bullet ants (Paraponera), located in Central and South America, are considered to have the most painful sting of any insect, although it is usually not fatal to humans. This sting is given the highest rating on the Schmidt sting pain index. [80]

The sting of jack jumper ants can be fatal, [81] and an antivenom has been developed for it. [82]

Fire ants, Solenopsis spp., are unique in having a venom sac containing piperidine alkaloids. [83] Their stings are painful and can be dangerous to hypersensitive people. [84]

Trap-jaw ants of the genus Odontomachus are equipped with mandibles called trap-jaws, which snap shut faster than any other predatory appendages within the animal kingdom. [85] One study of Odontomachus bauri recorded peak speeds of between 126 and 230 km/h (78 and 143 mph), with the jaws closing within 130 microseconds on average. The ants were also observed to use their jaws as a catapult to eject intruders or fling themselves backward to escape a threat. [85] Before striking, the ant opens its mandibles extremely widely and locks them in this position by an internal mechanism. Energy is stored in a thick band of muscle and explosively released when triggered by the stimulation of sensory organs resembling hairs on the inside of the mandibles. The mandibles also permit slow and fine movements for other tasks. Trap-jaws also are seen in the following genera: Anochetus, Orectognathus, and Strumigenys, [85] plus some members of the Dacetini tribe, [86] which are viewed as examples of convergent evolution.

A Malaysian species of ant in the Camponotus cylindricus group has enlarged mandibular glands that extend into their gaster. If combat takes a turn for the worse, a worker may perform a final act of suicidal altruism by rupturing the membrane of its gaster, causing the content of its mandibular glands to burst from the anterior region of its head, spraying a poisonous, corrosive secretion containing acetophenones and other chemicals that immobilise small insect attackers. The worker subsequently dies. [87]

Suicidal defences by workers are also noted in a Brazilian ant, Forelius pusillus, where a small group of ants leaves the security of the nest after sealing the entrance from the outside each evening. [88]

In addition to defence against predators, ants need to protect their colonies from pathogens. Some worker ants maintain the hygiene of the colony and their activities include undertaking or necrophory, the disposal of dead nest-mates. [89] Oleic acid has been identified as the compound released from dead ants that triggers necrophoric behaviour in Atta mexicana [90] while workers of Linepithema humile react to the absence of characteristic chemicals (dolichodial and iridomyrmecin) present on the cuticle of their living nestmates to trigger similar behaviour. [91]

Nests may be protected from physical threats such as flooding and overheating by elaborate nest architecture. [92] [93] Workers of Cataulacus muticus, an arboreal species that lives in plant hollows, respond to flooding by drinking water inside the nest, and excreting it outside. [94] Camponotus anderseni, which nests in the cavities of wood in mangrove habitats, deals with submergence under water by switching to anaerobic respiration. [95]

Learning

Many animals can learn behaviours by imitation, but ants may be the only group apart from mammals where interactive teaching has been observed. A knowledgeable forager of Temnothorax albipennis can lead a naïve nest-mate to newly discovered food by the process of tandem running. The follower obtains knowledge through its leading tutor. The leader is acutely sensitive to the progress of the follower and slows down when the follower lags and speeds up when the follower gets too close. [96]

Controlled experiments with colonies of Cerapachys biroi suggest that an individual may choose nest roles based on her previous experience. An entire generation of identical workers was divided into two groups whose outcome in food foraging was controlled. One group was continually rewarded with prey, while it was made certain that the other failed. As a result, members of the successful group intensified their foraging attempts while the unsuccessful group ventured out fewer and fewer times. A month later, the successful foragers continued in their role while the others had moved to specialise in brood care. [97]

Nest construction

Complex nests are built by many ant species, but other species are nomadic and do not build permanent structures. Ants may form subterranean nests or build them on trees. These nests may be found in the ground, under stones or logs, inside logs, hollow stems, or even acorns. The materials used for construction include soil and plant matter, [69] and ants carefully select their nest sites Temnothorax albipennis will avoid sites with dead ants, as these may indicate the presence of pests or disease. They are quick to abandon established nests at the first sign of threats. [98]

The army ants of South America, such as the Eciton burchellii species, and the driver ants of Africa do not build permanent nests, but instead, alternate between nomadism and stages where the workers form a temporary nest (bivouac) from their own bodies, by holding each other together. [99]

Weaver ant (Oecophylla spp.) workers build nests in trees by attaching leaves together, first pulling them together with bridges of workers and then inducing their larvae to produce silk as they are moved along the leaf edges. Similar forms of nest construction are seen in some species of Polyrhachis. [100]

Formica polyctena, among other ant species, constructs nests that maintain a relatively constant interior temperature that aids in the development of larvae. The ants maintain the nest temperature by choosing the location, nest materials, controlling ventilation and maintaining the heat from solar radiation, worker activity and metabolism, and in some moist nests, microbial activity in the nest materials. [101]

Some ant species, such as those that use natural cavities, can be opportunistic and make use of the controlled micro-climate provided inside human dwellings and other artificial structures to house their colonies and nest structures. [102] [103]

Cultivation of food

Most ants are generalist predators, scavengers, and indirect herbivores, [17] but a few have evolved specialised ways of obtaining nutrition. It is believed that many ant species that engage in indirect herbivory rely on specialized symbiosis with their gut microbes [104] to upgrade the nutritional value of the food they collect [105] and allow them to survive in nitrogen poor regions, such as rainforest canopies. [106] Leafcutter ants (Atta and Acromyrmex) feed exclusively on a fungus that grows only within their colonies. They continually collect leaves which are taken to the colony, cut into tiny pieces and placed in fungal gardens. Ergates specialise in related tasks according to their sizes. The largest ants cut stalks, smaller workers chew the leaves and the smallest tend the fungus. Leafcutter ants are sensitive enough to recognise the reaction of the fungus to different plant material, apparently detecting chemical signals from the fungus. If a particular type of leaf is found to be toxic to the fungus, the colony will no longer collect it. The ants feed on structures produced by the fungi called gongylidia. Symbiotic bacteria on the exterior surface of the ants produce antibiotics that kill bacteria introduced into the nest that may harm the fungi. [107]

Navigation

Foraging ants travel distances of up to 200 metres (700 ft) from their nest [108] and scent trails allow them to find their way back even in the dark. In hot and arid regions, day-foraging ants face death by desiccation, so the ability to find the shortest route back to the nest reduces that risk. Diurnal desert ants of the genus Cataglyphis such as the Sahara desert ant navigate by keeping track of direction as well as distance travelled. Distances travelled are measured using an internal pedometer that keeps count of the steps taken [109] and also by evaluating the movement of objects in their visual field (optical flow). [110] Directions are measured using the position of the sun. [111] They integrate this information to find the shortest route back to their nest. [112] Like all ants, they can also make use of visual landmarks when available [113] as well as olfactory and tactile cues to navigate. [114] [115] Some species of ant are able to use the Earth's magnetic field for navigation. [116] The compound eyes of ants have specialised cells that detect polarised light from the Sun, which is used to determine direction. [117] [118] These polarization detectors are sensitive in the ultraviolet region of the light spectrum. [119] In some army ant species, a group of foragers who become separated from the main column may sometimes turn back on themselves and form a circular ant mill. The workers may then run around continuously until they die of exhaustion. [120]

Locomotion

The female worker ants do not have wings and reproductive females lose their wings after their mating flights in order to begin their colonies. Therefore, unlike their wasp ancestors, most ants travel by walking. Some species are capable of leaping. For example, Jerdon's jumping ant (Harpegnathos saltator) is able to jump by synchronising the action of its mid and hind pairs of legs. [121] There are several species of gliding ant including Cephalotes atratus this may be a common trait among arboreal ants with small colonies. Ants with this ability are able to control their horizontal movement so as to catch tree trunks when they fall from atop the forest canopy. [122]

Other species of ants can form chains to bridge gaps over water, underground, or through spaces in vegetation. Some species also form floating rafts that help them survive floods. [123] These rafts may also have a role in allowing ants to colonise islands. [124] Polyrhachis sokolova, a species of ant found in Australian mangrove swamps, can swim and live in underwater nests. Since they lack gills, they go to trapped pockets of air in the submerged nests to breathe. [125]

Cooperation and competition

Not all ants have the same kind of societies. The Australian bulldog ants are among the biggest and most basal of ants. Like virtually all ants, they are eusocial, but their social behaviour is poorly developed compared to other species. Each individual hunts alone, using her large eyes instead of chemical senses to find prey. [126]

Some species (such as Tetramorium caespitum) attack and take over neighbouring ant colonies. Others are less expansionist, but just as aggressive they invade colonies to steal eggs or larvae, which they either eat or raise as workers or slaves. Extreme specialists among these slave-raiding ants, such as the Amazon ants, are incapable of feeding themselves and need captured workers to survive. [127] Captured workers of enslaved Temnothorax species have evolved a counter-strategy, destroying just the female pupae of the slave-making Temnothorax americanus, but sparing the males (who do not take part in slave-raiding as adults). [128]

Ants identify kin and nestmates through their scent, which comes from hydrocarbon-laced secretions that coat their exoskeletons. If an ant is separated from its original colony, it will eventually lose the colony scent. Any ant that enters a colony without a matching scent will be attacked. [129] Also, the reason why two separate colonies of ants will attack each other even if they are of the same species is because the genes responsible for pheromone production are different between them. The Argentine ant, however, does not have this characteristic, due to lack of genetic diversity, and has become a global pest because of it.

Parasitic ant species enter the colonies of host ants and establish themselves as social parasites species such as Strumigenys xenos are entirely parasitic and do not have workers, but instead, rely on the food gathered by their Strumigenys perplexa hosts. [130] [131] This form of parasitism is seen across many ant genera, but the parasitic ant is usually a species that is closely related to its host. A variety of methods are employed to enter the nest of the host ant. A parasitic queen may enter the host nest before the first brood has hatched, establishing herself prior to development of a colony scent. Other species use pheromones to confuse the host ants or to trick them into carrying the parasitic queen into the nest. Some simply fight their way into the nest. [132]

A conflict between the sexes of a species is seen in some species of ants with these reproducers apparently competing to produce offspring that are as closely related to them as possible. The most extreme form involves the production of clonal offspring. An extreme of sexual conflict is seen in Wasmannia auropunctata, where the queens produce diploid daughters by thelytokous parthenogenesis and males produce clones by a process whereby a diploid egg loses its maternal contribution to produce haploid males who are clones of the father. [133]

Relationships with other organisms

Ants form symbiotic associations with a range of species, including other ant species, other insects, plants, and fungi. They also are preyed on by many animals and even certain fungi. Some arthropod species spend part of their lives within ant nests, either preying on ants, their larvae, and eggs, consuming the food stores of the ants, or avoiding predators. These inquilines may bear a close resemblance to ants. The nature of this ant mimicry (myrmecomorphy) varies, with some cases involving Batesian mimicry, where the mimic reduces the risk of predation. Others show Wasmannian mimicry, a form of mimicry seen only in inquilines. [134] [135]

Aphids and other hemipteran insects secrete a sweet liquid called honeydew, when they feed on plant sap. The sugars in honeydew are a high-energy food source, which many ant species collect. [136] In some cases, the aphids secrete the honeydew in response to ants tapping them with their antennae. The ants in turn keep predators away from the aphids and will move them from one feeding location to another. When migrating to a new area, many colonies will take the aphids with them, to ensure a continued supply of honeydew. Ants also tend mealybugs to harvest their honeydew. Mealybugs may become a serious pest of pineapples if ants are present to protect mealybugs from their natural enemies. [137]

Myrmecophilous (ant-loving) caterpillars of the butterfly family Lycaenidae (e.g., blues, coppers, or hairstreaks) are herded by the ants, led to feeding areas in the daytime, and brought inside the ants' nest at night. The caterpillars have a gland which secretes honeydew when the ants massage them. Some caterpillars produce vibrations and sounds that are perceived by the ants. [138] A similar adaptation can be seen in Grizzled skipper butterflies that emit vibrations by expanding their wings in order to communicate with ants, which are natural predators of these butterflies. [139] Other caterpillars have evolved from ant-loving to ant-eating: these myrmecophagous caterpillars secrete a pheromone that makes the ants act as if the caterpillar is one of their own larvae. The caterpillar is then taken into the ant nest where it feeds on the ant larvae. [140] A number of specialized bacteria have been found as endosymbionts in ant guts. Some of the dominant bacteria belong to the order Hyphomicrobiales whose members are known for being nitrogen-fixing symbionts in legumes but the species found in ant lack the ability to fix nitrogen. [141] [142] Fungus-growing ants that make up the tribe Attini, including leafcutter ants, cultivate certain species of fungus in the genera Leucoagaricus or Leucocoprinus of the family Agaricaceae. In this ant-fungus mutualism, both species depend on each other for survival. The ant Allomerus decemarticulatus has evolved a three-way association with the host plant, Hirtella physophora (Chrysobalanaceae), and a sticky fungus which is used to trap their insect prey. [143]

Lemon ants make devil's gardens by killing surrounding plants with their stings and leaving a pure patch of lemon ant trees, (Duroia hirsuta). This modification of the forest provides the ants with more nesting sites inside the stems of the Duroia trees. [144] Although some ants obtain nectar from flowers, pollination by ants is somewhat rare, one example being of the pollination of the orchid Leporella fimbriata which induces male Myrmecia urens to pseudocopulate with the flowers, transferring pollen in the process. [145] One theory that has been proposed for the rarity of pollination is that the secretions of the metapleural gland inactivate and reduce the viability of pollen. [146] [147] Some plants have special nectar exuding structures, extrafloral nectaries, that provide food for ants, which in turn protect the plant from more damaging herbivorous insects. [148] Species such as the bullhorn acacia (Acacia cornigera) in Central America have hollow thorns that house colonies of stinging ants (Pseudomyrmex ferruginea) who defend the tree against insects, browsing mammals, and epiphytic vines. Isotopic labelling studies suggest that plants also obtain nitrogen from the ants. [149] In return, the ants obtain food from protein- and lipid-rich Beltian bodies. In Fiji Philidris nagasau (Dolichoderinae) are known to selectively grow species of epiphytic Squamellaria (Rubiaceae) which produce large domatia inside which the ant colonies nest. The ants plant the seeds and the domatia of young seedling are immediately occupied and the ant faeces in them contribute to rapid growth. [150] Similar dispersal associations are found with other dolichoderines in the region as well. [151] Another example of this type of ectosymbiosis comes from the Macaranga tree, which has stems adapted to house colonies of Crematogaster ants. [152]

Many plant species have seeds that are adapted for dispersal by ants. [153] Seed dispersal by ants or myrmecochory is widespread, and new estimates suggest that nearly 9% of all plant species may have such ant associations. [154] [153] Often, seed-dispersing ants perform directed dispersal, depositing the seeds in locations that increase the likelihood of seed survival to reproduction. [155] Some plants in arid, fire-prone systems are particularly dependent on ants for their survival and dispersal as the seeds are transported to safety below the ground. [156] Many ant-dispersed seeds have special external structures, elaiosomes, that are sought after by ants as food. [157]

A convergence, possibly a form of mimicry, is seen in the eggs of stick insects. They have an edible elaiosome-like structure and are taken into the ant nest where the young hatch. [158]

Most ants are predatory and some prey on and obtain food from other social insects including other ants. Some species specialise in preying on termites (Megaponera and Termitopone) while a few Cerapachyinae prey on other ants. [108] Some termites, including Nasutitermes corniger, form associations with certain ant species to keep away predatory ant species. [159] The tropical wasp Mischocyttarus drewseni coats the pedicel of its nest with an ant-repellent chemical. [160] It is suggested that many tropical wasps may build their nests in trees and cover them to protect themselves from ants. Other wasps, such as A. multipicta, defend against ants by blasting them off the nest with bursts of wing buzzing. [161] Stingless bees (Trigona and Melipona) use chemical defences against ants. [108]

Flies in the Old World genus Bengalia (Calliphoridae) prey on ants and are kleptoparasites, snatching prey or brood from the mandibles of adult ants. [162] Wingless and legless females of the Malaysian phorid fly (Vestigipoda myrmolarvoidea) live in the nests of ants of the genus Aenictus and are cared for by the ants. [162]

Fungi in the genera Cordyceps and Ophiocordyceps infect ants. Ants react to their infection by climbing up plants and sinking their mandibles into plant tissue. The fungus kills the ants, grows on their remains, and produces a fruiting body. It appears that the fungus alters the behaviour of the ant to help disperse its spores [163] in a microhabitat that best suits the fungus. [164] Strepsipteran parasites also manipulate their ant host to climb grass stems, to help the parasite find mates. [165]

A nematode (Myrmeconema neotropicum) that infects canopy ants (Cephalotes atratus) causes the black-coloured gasters of workers to turn red. The parasite also alters the behaviour of the ant, causing them to carry their gasters high. The conspicuous red gasters are mistaken by birds for ripe fruits, such as Hyeronima alchorneoides, and eaten. The droppings of the bird are collected by other ants and fed to their young, leading to further spread of the nematode. [166]

A study of Temnothorax nylanderi colonies in Germany found that workers parasitized by the tapeworm Anomotaenia brevis (ants are intermediate hosts, the definitive hosts are woodpeckers) lived much longer than unparasitized workers and had a reduced mortality rate, comparable to that of the queens of the same species, which live for as long as two decades. [167]

South American poison dart frogs in the genus Dendrobates feed mainly on ants, and the toxins in their skin may come from the ants. [168]

Army ants forage in a wide roving column, attacking any animals in that path that are unable to escape. In Central and South America, Eciton burchellii is the swarming ant most commonly attended by "ant-following" birds such as antbirds and woodcreepers. [169] [170] This behaviour was once considered mutualistic, but later studies found the birds to be parasitic. Direct kleptoparasitism (birds stealing food from the ants' grasp) is rare and has been noted in Inca doves which pick seeds at nest entrances as they are being transported by species of Pogonomyrmex. [171] Birds that follow ants eat many prey insects and thus decrease the foraging success of ants. [172] Birds indulge in a peculiar behaviour called anting that, as yet, is not fully understood. Here birds rest on ant nests, or pick and drop ants onto their wings and feathers this may be a means to remove ectoparasites from the birds.

Anteaters, aardvarks, pangolins, echidnas and numbats have special adaptations for living on a diet of ants. These adaptations include long, sticky tongues to capture ants and strong claws to break into ant nests. Brown bears (Ursus arctos) have been found to feed on ants. About 12%, 16%, and 4% of their faecal volume in spring, summer and autumn, respectively, is composed of ants. [173]

Ants perform many ecological roles that are beneficial to humans, including the suppression of pest populations and aeration of the soil. The use of weaver ants in citrus cultivation in southern China is considered one of the oldest known applications of biological control. [174] On the other hand, ants may become nuisances when they invade buildings, or cause economic losses.

In some parts of the world (mainly Africa and South America), large ants, especially army ants, are used as surgical sutures. The wound is pressed together and ants are applied along it. The ant seizes the edges of the wound in its mandibles and locks in place. The body is then cut off and the head and mandibles remain in place to close the wound. [175] [176] [177] The large heads of the dinergates (soldiers) of the leafcutting ant Atta cephalotes are also used by native surgeons in closing wounds. [178]

Some ants have toxic venom and are of medical importance. The species include Paraponera clavata (tocandira) and Dinoponera spp. (false tocandiras) of South America [179] and the Myrmecia ants of Australia. [180]

In South Africa, ants are used to help harvest the seeds of rooibos (Aspalathus linearis), a plant used to make a herbal tea. The plant disperses its seeds widely, making manual collection difficult. Black ants collect and store these and other seeds in their nest, where humans can gather them en masse. Up to half a pound (200 g) of seeds may be collected from one ant-heap. [181] [182]

Although most ants survive attempts by humans to eradicate them, a few are highly endangered. These tend to be island species that have evolved specialized traits and risk being displaced by introduced ant species. Examples include the critically endangered Sri Lankan relict ant (Aneuretus simoni) and Adetomyrma venatrix of Madagascar. [183]

E. O. Wilson has estimated that the total number of individual ants alive in the world at any one time is between one and ten quadrillion (short scale) (i.e., between 10 15 and 10 16 ). According to this estimate, the total biomass of all the ants in the world is approximately equal to the total biomass of the entire human race. [184] According to this estimate, there are also approximately 1 million ants for every human on Earth. [185]

As food

Ants and their larvae are eaten in different parts of the world. The eggs of two species of ants are used in Mexican escamoles. They are considered a form of insect caviar and can sell for as much as US$40 per pound ($90/kg) because they are seasonal and hard to find. In the Colombian department of Santander, hormigas culonas (roughly interpreted as "large-bottomed ants") Atta laevigata are toasted alive and eaten. [186]

In areas of India, and throughout Burma and Thailand, a paste of the green weaver ant (Oecophylla smaragdina) is served as a condiment with curry. [187] Weaver ant eggs and larvae, as well as the ants, may be used in a Thai salad, yam (Thai: ยำ ), in a dish called yam khai mot daeng (Thai: ยำไข่มดแดง ) or red ant egg salad, a dish that comes from the Issan or north-eastern region of Thailand. Saville-Kent, in the Naturalist in Australia wrote "Beauty, in the case of the green ant, is more than skin-deep. Their attractive, almost sweetmeat-like translucency possibly invited the first essays at their consumption by the human species". Mashed up in water, after the manner of lemon squash, "these ants form a pleasant acid drink which is held in high favor by the natives of North Queensland, and is even appreciated by many European palates". [188]

In his First Summer in the Sierra, John Muir notes that the Digger Indians of California ate the tickling, acid gasters of the large jet-black carpenter ants. The Mexican Indians eat the replete workers, or living honey-pots, of the honey ant (Myrmecocystus). [188]

As pests

Some ant species are considered as pests, primarily those that occur in human habitations, where their presence is often problematic. For example, the presence of ants would be undesirable in sterile places such as hospitals or kitchens. Some species or genera commonly categorized as pests include the Argentine ant, immigrant pavement ant, yellow crazy ant, banded sugar ant, pharaoh ant, red wood ant, black carpenter ant, odorous house ant, red imported fire ant, and European fire ant. Some ants will raid stored food, some will seek water sources, others may damage indoor structures, some may damage agricultural crops directly (or by aiding sucking pests). Some will sting or bite. [189] The adaptive nature of ant colonies make it nearly impossible to eliminate entire colonies and most pest management practices aim to control local populations and tend to be temporary solutions. Ant populations are managed by a combination of approaches that make use of chemical, biological, and physical methods. Chemical methods include the use of insecticidal bait which is gathered by ants as food and brought back to the nest where the poison is inadvertently spread to other colony members through trophallaxis. Management is based on the species and techniques may vary according to the location and circumstance. [189]

In science and technology

Observed by humans since the dawn of history, the behaviour of ants has been documented and the subject of early writings and fables passed from one century to another. Those using scientific methods, myrmecologists, study ants in the laboratory and in their natural conditions. Their complex and variable social structures have made ants ideal model organisms. Ultraviolet vision was first discovered in ants by Sir John Lubbock in 1881. [190] Studies on ants have tested hypotheses in ecology and sociobiology, and have been particularly important in examining the predictions of theories of kin selection and evolutionarily stable strategies. [191] Ant colonies may be studied by rearing or temporarily maintaining them in formicaria, specially constructed glass framed enclosures. [192] Individuals may be tracked for study by marking them with dots of colours. [193]

The successful techniques used by ant colonies have been studied in computer science and robotics to produce distributed and fault-tolerant systems for solving problems, for example Ant colony optimization and Ant robotics. This area of biomimetics has led to studies of ant locomotion, search engines that make use of "foraging trails", fault-tolerant storage, and networking algorithms. [194]

As pets

From the late 1950s through the late 1970s, ant farms were popular educational children's toys in the United States. Some later commercial versions use transparent gel instead of soil, allowing greater visibility at the cost of stressing the ants with unnatural light. [195]

In culture

Anthropomorphised ants have often been used in fables and children's stories to represent industriousness and cooperative effort. They also are mentioned in religious texts. [196] [197] In the Book of Proverbs in the Bible, ants are held up as a good example for humans for their hard work and cooperation. [198] Aesop did the same in his fable The Ant and the Grasshopper. In the Quran, Sulayman is said to have heard and understood an ant warning other ants to return home to avoid being accidentally crushed by Sulayman and his marching army. [Quran 27:18] , [199] [200] In parts of Africa, ants are considered to be the messengers of the deities. Some Native American mythology, such as the Hopi mythology, considers ants as the very first animals. Ant bites are often said to have curative properties. The sting of some species of Pseudomyrmex is claimed to give fever relief. [201] Ant bites are used in the initiation ceremonies of some Amazon Indian cultures as a test of endurance. [202] [203]

Ant society has always fascinated humans and has been written about both humorously and seriously. Mark Twain wrote about ants in his 1880 book A Tramp Abroad. [204] Some modern authors have used the example of the ants to comment on the relationship between society and the individual. Examples are Robert Frost in his poem "Departmental" and T. H. White in his fantasy novel The Once and Future King. The plot in French entomologist and writer Bernard Werber's Les Fourmis science-fiction trilogy is divided between the worlds of ants and humans ants and their behaviour is described using contemporary scientific knowledge. H.G. Wells wrote about intelligent ants destroying human settlements in Brazil and threatening human civilization in his 1905 science-fiction short story, The Empire of the Ants. In more recent times, animated cartoons and 3-D animated films featuring ants have been produced including Antz, A Bug's Life, The Ant Bully, The Ant and the Aardvark, Ferdy the Ant and Atom Ant. Renowned myrmecologist E. O. Wilson wrote a short story, "Trailhead" in 2010 for The New Yorker magazine, which describes the life and death of an ant-queen and the rise and fall of her colony, from an ants' point of view. [205] The French neuroanatomist, psychiatrist and eugenicist Auguste Forel believed that ant societies were models for human society. He published a five volume work from 1921 to 1923 that examined ant biology and society. [206]

In the early 1990s, the video game SimAnt, which simulated an ant colony, won the 1992 Codie award for "Best Simulation Program". [207]

Ants also are quite popular inspiration for many science-fiction insectoids, such as the Formics of Ender's Game, the Bugs of Starship Troopers, the giant ants in the films Them! and Empire of the Ants, Marvel Comics' super hero Ant-Man, and ants mutated into super-intelligence in Phase IV. In computer strategy games, ant-based species often benefit from increased production rates due to their single-minded focus, such as the Klackons in the Master of Orion series of games or the ChCht in Deadlock II. These characters are often credited with a hive mind, a common misconception about ant colonies. [208]


Ant Reproduction

The life of an ant starts with an egg. If the egg is fertilized, the ant will be female if not, it will be male. Ants are holometabolous (a specific kind of insect development which includes four life stages) and develop by complete metamorphosis, passing through larval and pupal stages before they become adults.

The larval stage is particularly helpless – for instance it lacks legs entirely – and cannot care for itself. The difference between queens and workers (which are both female), and between different castes of workers when they exist, is determined by feeding in the larval stage. Food is given to the larvae by a process called ‘trophallaxis’ in which an ant regurgitates food previously held in its crop for communal storage. This is also how adults distribute food amongst themselves.

Larvae and pupae need to be kept at fairly constant temperatures to ensure proper development, and so are often moved around various brood chambers within the colony.

A new worker spends the first few days of its adult life caring for the queen and young. After that it graduates to digging and other nest work, and then to foraging and defense of the nest. These changes are fairly abrupt and define what are called temporal castes.

One theory of why this occurs is because foraging has a high death rate, so ants only participate in it when they are older and closer to death anyway. In a few ants there are also physical castes – workers come in a spectrum of sizes, called minor, median, and major workers, the latter beginning foraging sooner.

Often the larger ants will have disproportionately larger heads and so will have stronger mandibles. Such individuals are sometimes called ‘soldier’ ants because their stronger mandibles make them more effective in fighting other creatures, although they are still in fact worker ants and their ‘duties’ typically do not vary greatly from the minor or median workers. In a few species the median workers have disappeared, creating a sharp divide and clear physical difference between the minors and majors.

Most of the common ant species breed in the same way. Only the Queen and breeding females have the ability to mate. Some ant nests have multiple queens. The male ants, called drones, along with the breeding females are born with wings and do nothing throughout their life except eat, until the time for mating comes.

At this time, all breeding ants, excluding the queen, are carried outside where other colonies of similar species are doing the same. Then, all the winged breeding ants take flight. Mating occurs in flight and the males die shortly afterward. The females that survive land and seek a suitable place to begin a colony. There, they break off their own wings and begin to lay eggs, which they care for.

The first workers to hatch are weak and smaller than later workers, but they begin to serve the colony immediately. They enlarge the nest, forage for food and care for the other eggs. This is how most new colonies start.

Worker ants are sterile (do not breed), therefore their jobs are to look for food, protect the eggs, take care of the young, and defend the nest from unwanted visitors. During the night, the worker ants move the eggs and the larvae deep into the nest to protect them from the cold. During the daytime, the worker ants move the eggs and larvae of the colony to the top of the nest so that they can be warmer.

If a worker ant finds a good source of food, it leaves a trail of scent so that the other ants in the colony can find the food. Army Ants are nomadic and they are always moving. They carry their larvae and their eggs with them in a long trail.


How do ants spontaneously grow wings? - Biology

"long-legged ant" This ant is commonly found at low elevation areas throughout the islands. A quick moving large species.

"Argentine ant" This ant is a worldwide pest in Mediterranean climates, such as California, and is spreading its range at high elevations on Maui and the Big Island.

"big-headed ant" African ant first observed in Hawaii around the turn of the century, this ant is common throughout the islands and a prime suspect in the extinction of many lowland beetle species.

"Hawaiian carpenter ant" Although not originally from Hawaii, this ant was first discovered and described in Hawaii. It is a wood eater, commonly found in houses in dry leeward areas of Hawaii.

One of several species of very small black ants. Common in many lowland areas in the islands.

"crazy ant" Worldwide tramp ant and pest, especially in dry areas. Named for its rapid, seemingly random movements.

"pharaoh ant" Common indoor pest.

"tiny yellow ant" A common house ant, it likes sweets.

"tropical fire ant" A common, aggressive red ant throughout the lowland Hawaiian Islands, in wet and dry areas, it packs a painful sting.

This ant is a relative newcomer to the Hawaiian Islands, but its populations are growing rapidly, and it is more and more commonly found in people's yards and kitchens, especially in Honolulu. It moves slowly in lines.


This “Useless” Organ Determines Which Ants Grow Into Large Soldiers

Ant colonies have evolved some surprising collective traits over the 150 million years or so that they have crawled the Earth. Fire ants link together to make frighteningly effective rafts, for example, and some army ants seem to instinctively build perfectly efficient ant bridges for collecting food.

These insects also seem to have the ability to control their populations, maintaining a set ratio of soldiers to workers. How such ant caste systems came to be is something of a mystery for entomologists, but a study published in Nature today reveals that whether an ant grows into a soldier or a worker has to do with an organ that was long thought useless—wing discs.

“These caste systems are one of the major unexplained phenomena of phenotypic evolution,” says Scott Powell, an ant biologist at The George Washington University in Washington D.C. “This study really identifies the main underlying control center that produces these castes.”

The wing discs, tiny pouches of cells, are destined to become wings on a queen, but they grow in the larvae and then die during metamorphosis to produce wingless soldiers. The study shows that these rudimentary wing discs are not so rudimentary after all, but rather affect the development of the ant larvae.

“The really important point about this work is that rudimentary organs and vestigial structures, which were long believed to have no function, might actually have major signaling roles during development,” says evolutionary developmental biologist Ehab Abouheif of McGill University, the senior author of the new study. (Disclaimer: I spoke with Abouheif about his research prior to publication and he has included me in the paper's acknowledgements.)

Developing soldier larvae produce large, rudimentary wing discs, while the larvae of workers do not. Previously thought to simply die away during metamorphosis, the wing discs apparently have some influence on the growth of other body parts.

“[The wing discs] do get quite big–it’s kind of surprising,” says Diana Wheeler, an ant biologist at the University of Arizona who has studied ant caste determination since the 1980s. “It’s evidently not something that evolution just forgot to get rid of. It seems like it’s being used for something.”

The apparent function of the ant larvae’s wing discs has significant implications for the insect’s evolutionary history. Early ants produced colonies with a winged queen and a wingless worker caste, and subsequently, in several independent lineages, the worker caste became further differentiated into subcastes. In Pheidole, a hyperdiverse genus that includes more than 1,000 species of ants, the worker caste is divided into minor workers and soldiers. Soldiers have disproportionately big heads which they use for defense and seed processing, while minor workers make up 90 to 95 percent of the colony and do tasks like brood rearing and foraging.

A Pheidole ant photographed in Canberra, Australia. (Steve Shattuck/Wikimedia Commons CC 3.0)

Wheeler’s studies from the 1980s demonstrated that Pheidole ants can regulate the proportion of minor workers and soldiers in the colony. One way this regulation works is through an inhibitory pheromone—a cuticular hydrocarbon—made by the soldiers that suppresses soldier development in larvae if soldiers exceed approximately five percent of the colony’s population.

To investigate the relationship between the wing discs and the soldier subcaste, Abouheif and his team knocked down a gene called vestigial, which causes the wing disc cells to die very early in development. Knocking down vestigial in soldier-destined larvae reduced the head size and body size of the animals, producing minor workers, while knocking down vestigial in minor workers produced no effect.

The team then raised soldier-destined larvae with adult populations of 100 percent minor workers or with 100 percent soldiers. With 100 percent minor workers in the colony, the larvae produced soldiers. But with 100 percent soldiers, giving off the cuticular hydrocarbon pheromone, the larvae’s rudimentary wing disc size was significantly reduced and produced adult ants with smaller heads and bodies.

Of course, the fact that organs affect the development of other organs within the body isn’t new. Previous experiments in insects have demonstrated that developing wings compete for nutrients and growth factors, for instance. Damage to a developing wing can produce signals that delay development across the whole body, allowing the disc time to recover so that growth can proceed in a properly coordinated way.

What’s striking here, according to first author Rajendhran Rajakumar, is that instead of being in competition, the rudimentary wing actually promotes the growth of the head in the soldier subcaste. “It’s even more surprising based on the fact that this tissue doesn’t actually form in the adults. It’s rudimentary, so we really didn’t expect to find the kind of results we did when we perturbed it,” says Rajakumar, who worked in Abouheif’s lab at McGill and is now a researcher at Harvard.

The ants contrast with other social insects like bees and wasps, which have not evolved worker polymorphisms. Queen and worker bees all have wings, and “if you are making a wing that must fly, you can’t really play around with its growth very much, so the growth of those discs is very constrained,” explains Abouheif. That may explain why worker bees, unlike ants, never evolutionarily differentiated further into subcastes.

There aren’t many known examples of rudimentary or vestigial organs driving evolutionary innovation. Other than the wing discs, another intriguing possibility is the ovary of a larval honeybee worker, which is as large as that of a queen during early stages of development. It’s not clear why the larval honeybee workers need ovaries, since they will never reproduce, says Mary Jane West-Eberhard, an evolutionary developmental biologist at the Smithsonian Tropical Research Institute.

“So the question would be: is it important for normal worker development to have the ovary present in the early larva?” she asks. Only future investigation will tell.

“I hope this work will lead people to look at what they think of vestigial organs in a different way, and that they try to probe what those things are actually doing, instead of just dismissing them as just a leftover thing,” Abouheif says. “I think actually they’re playing much bigger roles than we had thought previously.”


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