ANTS
Ants have been around for at least 140 million years, and they are believed to have evolved from wasps. There are 12,000 known ant species (1.4 percent of all known insect species) and an estimated ten thousand trillion individuals ants. Their total weight is about equal to all the people in the world and is ten times that of all other insects combined. They are found in every part of the world except the polar ice caps and permanently ice-bound mountains. [Source: Bert Hölldobler, National Geographic June 1984 [┶]
If any group of species were to be labeled as king of the jungle it would have to be ants. They, not lions (who don't live in the jungle anyway), rule in terms of numbers, ferocity and organization. Describing an encounter with a hostile group of ants Harvard biologist and ant expert Edmund O. Wilson lamented: "The little defenders were under my clothing, in my hair, running over my eyeglasses. I had to stop frequently to clean myself off, and finally I gave up. But that, of course, is the point. I was Gulliver tied down by the Lilliputians in a successful defense of their land. Although I was 80 million heavier than each ant, the tribe prevailed."▸
Many ants and termites spend their whole life underground. Those that dig often lack eyes and have narrow bodies. They generally excavate the earth with their mouths.
Ants are omnivorous. Typically a species will eat a mix of aphid feces, cricket wings, other ants, spingtails and seeds. They are the largest consumer of other insects and the primary scavenger of small dead bodies.
Websites and Resources on Ants: Antweb antweb.org ; Abt Blog antblog.co.uk ; Wikipedia article Wikipedia ; Antbase Database antbase.org ; Ant Genera, World Location antmacroecology.org/ant_genera/index ; Discover Life Ants discoverlife.org/20/q’search=Formicidae ; BugGuide bugguide.net/node/view/165 ; Antstuff antstuff.net/html/species_of_ants ; Terminix terminix-triad.com/ants ;
Book: “Adventures Among Ants: A Global Safari with a cast of Trillions” by Mark Moffett
Websites and Resources on Insects: Insect.org insects.org ; Insect Images.org insectimages.org ; BBC Insects bbc.co.uk/nature/life/Insect ; Insect and Arachnid entomology.umn.edu/cues/4015/morpology ; Wikipedia article Wikipedia ; Virtual Insect home.comcast.net ; National Geographic on Bugs National Geographic ; Smithsonian bug info si.edu/Encyclopedia_SI/nmnh/buginfo ; Entomology for Beginners bijlmakers.com/entomology/begin ; BugGuide bugguide.net ;
Websites and Resources on Animals: ARKive arkive.org Animal Info animalinfo.org ; Animal Picture Archives (do a Search for the Animal Species You Want) animalpicturesarchive ; BBC Animals Finder bbc.co.uk/nature/animals ; Animal Diversity Web animaldiversity.ummz.umich.edu ; International Field Guides media.library.uiuc.edu ; animals.com animals.com/tags/animals-z ; Encyclopedia of Life eol.org ; World Wildlife Fund (WWF) worldwildlife.org ; National Geographic National Geographic ; Animal Planet animal.discovery.com ; Wikipedia article on Animals Wikipedia ; Animals.com animals.com ; Endangered Animals iucnredlist.org ; Endangered Species Resource List ucblibraries.colorado.edu ; Biodiversity Heritage Library biodiversitylibrary.org
Ant Colonies
Like termites, ants live in colonies in which the vast majority of the members work their butts off gathering food, tending young, fending off intruders and building living space to support a structure that allows one or a few individuals to reproduce. Ants are unable to live alone. They do everything for the common good of the colony.
Ant colonies, which may have a million or more individuals, are made up entirely females produced by a single queen. Their sole purpose in life is to protect the queen and make sure that enough food is gathered to feed the next generation. The Japanese word for ant — written by joining the Chinese characters for “insect” and “loyalty”’seems like an apt way to sum up their existence.
See Termites
Male and Female Ants
All ant societies consist entirely of females. Males come into existence for only a short time to fertilize the queen and then die. Almost all ants in a colony are daughters of the same queen. They are made infertile by chemicals and their size and caste is determined by the food they are given. Each ant on average shares 75 percent of her sister' genes. These ants have no chance of reproducing so it makes sense from an evolutionary point of view for them to die for good of colony.
Males are created on rare occasions when a female destined to be a queen becomes fertile. They are hatched from eggs unfertilized by the queen and their production is signaled by natural occurrences. They don't live for very long and their sole purpose in life is to mate with the queen.
The males and the virgin female slated to be queen have wings. If a male is lucky enough to locate the fertile female he grabs onto her with his mandibles. Some males blow their opportunity, grabbing the female too hard and cutting her abdomen in two. The queen tries to mate with as many males as possible to fill her abdomen with enough sperm to last a lifetime and fertilize millions of eggs. The transfer of sperm takes place in mid flight.
Queens, Soldiers and Worker Ants
After the queen's abdomen is full of sperm she produces a vibrational signal letting the males know it is time for them to let go. She then flies off and, after she located a nesting site, she sheds hew wings and buries herself into the ground to raise her young. Once she has established here colony she never sees the light of day unless scientist or an ant-eating animals digs her up. The first generation of offspring are fed from her own body reserves.
The vast majority of the colony is made up of worker ants who perform a variety of duties and will sacrifice themselves at a moment's notice for the colony. They often live only a few months and are divided by size into minors, media, submajors and majors, which each size responsible for a specific duty such a carrying prey or feeding the queen’s larva. Soldier ants, or majors, are in charge of defending the colony. They may be a hundred times bigger than the smallest worker ants. Some are so ferocious they will even attack encroaching plants.
Once a colony is established the queen is taken care of at all times by workers who feed her sterile eggs and regurgitate food. Responding to chemicals given off by the queen the workers of some species of ant vigorously lick and groom their mother's body. The queen lives for several years. If she dies before a new queen is born the colony is thrown into chaos and often collapses.
Ant Communication
Ants are for all intents and purposes blind and deaf. To get around, communicate and gain information about their world they rely on touch from the sensitive antennae and the smell of chemicals called pheromones, that are secreted and sensed by smell and taste are used like language to communicate warnings and instructions.
Wilson wrote in National Geographic: “The communications systems of ants are radically nonhuman. Where we use sound and sight, they depend primarily on pheromones...Since the brain of an ant weighs less one-millionth as much as a human brain, it is not surprising that a given species produces just ten to twenty signals. Unlike human language, these messages are entirely instinctual.”
Pheromones convey messages about the presence of danger and food, identify ants as friends or foe, and provide information about the rearing of young. Weaver ants release a series of pheromone that call for reinforcements when they bite an intruder and relay information about the location of food by leaving pheromones trails. Some species have huge workers that are signaled by pheromones to attack large intruders such as human, armadillos or anteaters.
See Leaf-cutter ants
Navigating Ants
University of Zurich biologist Rüdiger Wehner discovered that some ants navigate by following directional cues such as the way light from the sun is polarized at certain times of the day. In a study of Tunisian ants that scamper across 160̊F desert sands to collect victims that die in the heat he discovered that an ant's eye has "80 lenses dedicated to receiving polarized light in the ultra-violent range of the spectrum, each from a different point in the sky.”
"One lens from 180 degrees, another from 270 degrees and so on," says Werner." To his test his theory he built a device that look like a lawn mower to mask the polarity. In accordance with his theory ants have difficulty finding their way around but observers thought he was trying to mow the desert. [Michael E. Long, National Geographic, June 1991]
German researchers found ants some in the Sahara that using a zag zag pattern when looking for food but take a direct route home found that do so in part by counting their steps. The scientist discovered this by clipping the legs of some ants and lengthening the legs of others . Those had their legs clipped began look for their nest before they arrived and those that had their legs lengthened overshot their target.
Ant Group Behavior
As individuals ants are often clueless about what they are trying to do. “If you watch an ant trying to accomplish something you’ll be impressed by how inept it is,” Deborah Gordon, a biologist at Stanford University, told National Geographic.
“A colony can solve problems unthinkable for individual ants,” Peter Miller wrote in National Geographic, “Such as finding the shortest path to the best food source, allocating workers to different tasks, or defending a territory from neighbors. As individuals, ants might be tiny dummies, but as colonies they respond quickly and effectively to their environment.”
“One key to an ant colony,” Peter Miller wrote in National Geographic, “is that no one’s in charge. No generals command ant warriors. No managers boss ant workers. The queen plays no role except to lay eggs. Even with a half million ants, a colony functions just fine with no management at all — at least none that we would recognize. It relies instead upon countless interactions between individual ants, each of which is following simple rules of thumb. Scientist describe such a system as self-organizing.”
Research by Gordon with harvester ants reveals that each day the colony calculates how many ants to send out to forage for food, with the number changing based on changing conditions. The first members of the colony that go out are patrolling ants. Foragers and workers wait for the patrollers to return before going out and the rate of the patrollers return determines whether they go out. “When a forager has contact with a patroller it is a stimulus for the forager to go out,” Gordan said. “But the foragers needs several contacts less than ten second apart before it will go out.” Gordon made this discovery by dropping beads’some scented with patroller scent and some scented with worker scent — at the entrance of their nest and found that foragers only responded to the beads with patroller scent. She also found that once the foraging process gets going the rate foragers go out depends on the return rate of the foragers that went before them.
The behavior described above can be explained by swarm intelligence, which is base on the idea that creatures abide by simple rules, each individual acting on local information . No individual sees the picture, no one tells individuals what to do, no leadership is needed. Oxford biologist Iain Couzin told National Geographic, “Even complex behavior may be coordinated by relatively simple interactions.” In 1991, Marco Dorigo, a computer scientists at the University of Brussels, created a mathematical model to solve complex human problems based on ant behavior. The model has been particularly useful to trucking firms trying to figure out the best way to distribute their goods and airlines determining the best way to get their planes in and out of gates and customers in and out of check in counters.
Studies of army ants by Iain Couzin of Oxford University found that the behavior of workers was different depending on whether they were heading away from the nest or heading towards it, with those heading back more or less moving in a straight line and those go out making slight turns when they encountered ants coming the other way. Using these methods ants were able to move rapidly along a sort of highway that had only just been created with a pheronome trail.
Ant Hunting and Enslavement
Many ants are carnivorous. They are especially fond of termites. Many species specialize by raiding termite colonies. Ants themselves are preyed upon by a host of creatures including white-plumed antbirds and body-invading fungus.
Mark Moffett, an ant expert and research associate at the Smithsonian Institute, told the Los Angeles Times, “Most ants either hunt on their own or send out scouts to search individually. You can spread out and look around alone, because in spreading apart, you’re to have a greater chance of finding something. But after one of the scouts doesn’t find something’say a prey she wants to kill’she often has to go get help, which give the prey lots of time to escape...Mass hunting is searching in a group. Army ants put soldiers together in a tight group that moves forward together. When they find something, they use the shock-and-awe effect. You find less but kill more.”
Some kind of ants make slaves of other species of ant, raiding colonies of the slave ants and seizing their pupae and make slaves them. Moffet said, “All you have to do is trick a young ant into thinking it is part of your colony and it will work to death for you.”
Ants and Other Living Things
Some ants tend aphids and mealybugs and feed on their sweet, slimy excrement sometimes called honey-dew. The aphids are tended like cattle and goaded into producing more honeydew than they otherwise would by stroking their antennae and squirting them with formic acid. When the aphids die their eggs are carefully incubated so a new generation can be raised.
Many ants have a birds-and bee-like relationship with plants in which the plant provides the ants with food, often in the form of nectar, while the ants help to spread pollen and fertilize the plants. Some ants also defend plants against pests in return for food, often nectar. [Source: Mark Moffett, National Geographic, February 1999 and May 1999]
Thousands of plants rely on ants to disperse their seeds. Many ant species collect seed of certain plants and take them to their colonies, helping the plants germinate by providing them with nutrients to grow. In many cases the ants are tricked into gardening the seeds. Many seeds contain a small fatty appendage known as an elaisome which attracts ants. The elaisome is fed to larvae and the rest of the seed is thrown with other ant garbage that not coincidently provides the seed with nutrients that help it grow.
Often when a seed falls off a tree ants will show up to carry it back to their nest, often by grasping the elaisome with their mandibles. Some colonies handles tens of thousands of seeds. Plants are thought to have evolved the elaisomes as means to getting a seed to a more advantageous spot. Seeds on the forest floor often have few other options than relying on ants. Birds and flying insects are fine for distributing seeds on the trees but are not so good at dispersing ones on ground level. Some questions about the method remain, such as why ants don’t just remove the elaisome instead of carry the whole seed back to their nest and what help the ants offer the plants in that they generally don’t move the seeds very far from where they fall.
Ancient Species of Ant
“Nothomyrmecia macrops” is a species of ant that is virtually identical to ant species that roamed the earth 100 million years ago. These ants form only small colonies with about 80 individuals, compared to other species with form colonies with hundreds of thousands of members, and forage at night when other insects, sluggish from the near freezing cold, are easy prey.
Up until the late 1970s only two specimens of these "holy grails of the ant world" had been found and they were collected by the niece of amateur naturalist on a summer outing at remote Cape Arid in Western Australia. In 1977 entomologist Robert was traveling to this cape to look for specimens when his car developed brake trouble several hundred miles before his destination. While the brakes were being fixed he wandered into the bush to relieve himself to his surprise he found a colony of “ Nothomyrmecia macrops” . Since his famous leak 70 other colonies have been found in an area called Poochera.
Army Ants
Army ants are found mostly in the tropical rain forests of Asia, Africa, Australia and the Americas. There are 320 known species of them with 150 in the New World, mostly in tropical areas of Central America and northern South America. In Africa they are called drivers. In South America they can form armies three quarters of million strong. Army ants in the Old World and the New World are thought to have independently evolved the same lifestyle and method of hunting. [Source: Mark W. Moffet, National Geographic, August 2006]
Unlike most other ant species, army ants don't form permanent colonies. Instead the roam across the forest floor in armies with several hundred thousand individuals that cover the earth like a living layer of soil, reaching for prey. A typical colony of an army ant species is comprised of five kinds of ants: the queen and four sizes of workers — minors, media, submajors and majors — which live only a few months. The three smallest workers kill and carry prey, feed the queen’s larva an maintain trails. The majors, or soldiers defend the colony.
The soldiers often have huge, sharp, hook-like jaws. Clumsy at anything but intimidating and fighting, they patrol the edge of trails and confront anything that seems threatening. Soldiers that put to up fights essentially commit themselves to suicide mission because once they sink their jaws into something the hook like designs of their jaws prevents them from being extracted. Many species use the jaws to gain a firm grip and then deliver a nasty, poisonous sting from their abdomen. Amazon tribes have traditionally used soldier ant as sutures, letting the ants bite into a wound and cutting off the body and leaving the heads in place.
Army Ant Balls
Instead of forming permanent nests in trees or in the ground, army ants form temporary nests called bivoucs made up of masses of ants linked together like trapeze artists underneath a log or woody overhang or some other objects. The interlocked ants form balls that be two or three feet in diameter, complete with passageways formed by individual ants. At the center of the ball is the queen.
Describing an army ant ball, David Attenborough wrote: "The outside surface is formed by a lacy sheet of soldiers, their legs linked together, their huge jaws agape, ready to slice into anything that might interfere with them. Within the mass, the smaller workers have in a similar fashion created chambers in which the pupae hang. And at the heart of the community sits the queen. She is almost an inch long, twice he length of any other individuals in her army. Her body glistens with a special polish for she is continually groomed by her servants.
A colony typical establishes a bivouac at a site for about 20 days. During that time the queen works overtime to produce eggs and may lay as many as 300,000 eggs while workers conduct raids in a different direction every day to make sure they don’t cover the same territory twice. When the eggs have hatched into pupae and pupae have become workers, and food sources have been depleted the army moves on.
Army Ants on the Move
Army ant colonies alternate between periods of living in bivouacs and periods when they are on the march. Their When they are on the move the ants cover 100 meters a day for two weeks to a month, move, raiding as they go and bivouacking along the way each night.
Army ants march in columns that may take several hours to pass a single spot. At the front are soldiers who scout for food. Behind them are workers, a dozen or so abreast, many carrying larvae. When the column stops soldiers race to the flanks, offering protection with the huge jaws.
When obstacles are reached they form ladders for other climb. They also construct canopies for protection from damaging sunshine. When army ants reach a depression they quickly build bridges so they cab keep moving as quickly as possible. Dr. Iain Couzin, a mathematical biologist at Oxford University, told the New York Times, “They build the bridge with their living bodies. They build them up if they’re required, and they dissolve them if they’re not being used.”
The column, which may contain hundreds of thousands of individuals, marches day after day. The larvae produce pheromones which keep the ants on the move. If rival army ant species meet by chnace they sometimes go to war. The battles featuring intimidating and sparing but generally end within an hour with a retreat and without any deaths.
Feeding Army Ants
Army ants form attack in formations called swarms that may consist of several hundred thousand ants and expand outward like a fan to a width of 15 meters. In some places specialized birds follow the swarm preying on insects that try to flee. If the soldier scouts locate any prey they swam all over it and cut it into pieces. On trails between the hunting sites and a bivouac, workers carrying prey travel down the center while outgoing ants travel on the sides.
Describing army ants on the hunt, David Attenborough wrote: "If they discover a grasshopper or beetle, they swarm all over it, sinking their jaws between the joints of its external skeleton and dismember it with surgical precision. The fragments may be eaten there and then or tucked away beside the column to be collected when the hunt is over and taken back to feed the queen and those who stayed back in the camp to tend and protect her."
Submajors carry the large pieces back to the bivouac, assisted by media workers whose job it is to make sure pieces don’t touch the ground. Often minors act as “living roadfill,” filling up pot holes to even out the path used by workers carrying prey. The workers that do the killing are often sprayed with blood-like hemolymph by their prey and are cleaned off by other workers when they return to the camp.
Army ants generally feed on spiders, roaches, grasshoppers, beetles and other ants. They will kill but generally not eat anything that gets in their way’scorpions, tarantulas, lizards, frogs and even small snakes. There are stories of creatures as large as dogs, horses, cattle, people and pythons being killed by army ants. In some parts of Africa tied up or penned up animals are sometimes killed by the painful, toxic bites of army ant swarms. The only way to deflect their onslaught is pour paraffin in the ground and set it on fire.
Mark W. Moffet wrote in National Geographic: “Armored tough, with machete jaws, these masterful fighters hack and dice prey vastly large than themselves by acting in numbers beyond easy comprehension...Being blind, they can’t see what’s ahead of them, but moving in such numbers they overwhelm their prey.”
Image Sources:
Text Sources: Mostly National Geographic articles. Also “Life on Earth” by David Attenborough (Princeton University Press), New York Times, Washington Post, Los Angeles Times, Smithsonian magazine, Natural History magazine, Discover magazine, Times of London, The New Yorker, Time, Newsweek, Reuters, AP, AFP, Lonely Planet Guides, Compton’s Encyclopedia and various books and other publications.
Last updated March 2011