In this lesson, you will explore the warring world of the army ant. We’ll discuss where they are found, what makes these ants different than other ants, and how their life cycle results in sedentary, roaming and active phases of their life.
Army Ants: A Name That Doesn’t Lie
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Most ants are merely a nuisance; they crawl on you outside or they try to sneak a chip at your picnic. All in all though, they seem pretty harmless. You may even have fond childhood memories singing, ‘The ants go marching two by two’, but, don’t let these particular ants fool you- they’re no joke. Army ants are more like pillaging hordes of invading barbarians rather than the sweet creatures you saw in Pixar’s A Bugs Life.The classification ‘army ant‘ is actually a general term that refers to any of about 18 genera (plural of genus) of ant that exhibit extremely aggressive nomadic behaviors and indiscriminately kill by overwhelming prey with their massive numbers. They’re also known as ‘driving ants’, ‘legionary ants’, or ‘visiting ants’ because they ‘visit’ but don’t stay; they pass through an area like a swarm of locusts and wipe out anything in their path.
There are about 12 thousand identified species of ant, but only about 200 are considered ‘army ants’.
While ants are ubiquitous, army ants only exist in hot and humid environments. They’re commonly found in the southern U.S., Central and Southern America, as well as Africa and Asia, however, not all army ants are created equal. U.S.
army ants, while being equally successful search and destroy drones as their African and Asian cousins, are not nearly as aggressive. In the U.S., if your house was in their path you wouldn’t have to worry about your chickens or small livestock, but some African and Asian species have been known to ‘take no prisoners’ and dismember livestock.
Within army ant society there are three main castes, or social roles: soldiers, workers, and the queen.Soldier ants are the largest of the nest. They have an oversized head and gigantic mandibles for defending and killing. Their mandibles are actually so large that soldier ants can’t feed without assistance from the smaller worker ants.
Worker ants are smaller in size and have smaller mandibles, but they are certainly no less aggressive. They are responsible for everything from fighting on the front lines, to carting food back to the nest, and caring for the queen and her eggs. Workers tend to live about a year, which, for a soldier ant, might equal more than a few of their lifetimes.On the other hand, the queen is protected and cared for by her colony; she is what unites the nest and so her survival is paramount. She can live anywhere from 10-20 years and tends to be the largest of the ants, with an oversized abdomen for accomplishing her reproductive needs. She is, in fact, the only reproductive female of the group. This means that the entire colony (some 300,000- 20 million ants) are most likely all her offspring.
What’s more is that the entire colony is female. Male ants get the ‘short end of the stick’ in that they are bred for reproductive needs only and then die about 48 hours after mating- that’s some tough luck boys!
Barbarian Hordes: Colony Structure ; Dynamic
Most ant species are solitary hunters and gatherers. They strike out on their own and, when food is found, they release a ‘dinner bell’-like pheromone to which the nest responds. This is why that one lonely ant at your picnic seems to multiply into a hundred in no time flat. Army ants aren’t nearly as covert about gathering food though.Army ant hunting groups, called swarm raids or column raids, can be 200,000-20 million ants strong, fanning out into a 15-110 yard wide swath of voracious killers. These raids aren’t random though- they fall into a carefully organized cycle based on the hatching and growth cycle of the young.
Army ants create temporary nests called bivouacs, either under cover of a fallen tree or out in the open. Open bivouacs are simply masses of ants that swarm, interlocking their legs and mandibles, around the queen and her brood to protect them.
These stationary phases last about 8-10 weeks, during which time the queen will mate and lay up to 30,000 eggs per day. After about twenty days the eggs hatch into worm-like larva that instigates the next phase of nomadic raiding.
During the nomadic phase, these colonies can kill up to 100,000 insects (spiders, scorpions, beetles, etc) and other unlucky creatures in their way per day. This makes army ants nature’s exterminators; they pass through an area and completely consume the entire insect population.
Now, this may seem like a huge inconvenience if you live in Africa or Asia and have to vacate your home for a few hours while an army ant raid works its way through your farm or house but, when you return, there won’t be a single bug in sight! This raiding phase ends when the larva pupate, or spin a cocoon shell, so that they may go through metamorphosis (a period of body modifications resulting in an adult ant).
Army ant is a general term that refers to some 200 of the 12,000 species of ants that share the common traits of nomadic behavior, extreme aggression, and massive hunting parties, called swarm raids or column raids. These ants form colonies that can be anywhere from 200,000-20 million individuals, all of which are infertile females, save for the queen.The army ant caste system includes three levels: soldiers (which are large and have massive fighting mandibles), workers (small ants that are equally aggressive fighters, as well as porters of food, and caretakers for the queen and her brood), and the queen, whose sole responsibility is to reproduce and replenish her stock of fighters.
Army ants cycle through a nomadic raiding phase and a temporary stationary phase, where they create bivouacs, or temporary nests. This cycle of nesting and raiding is a product of the stationary requirements of the egg laying and pupae phases (stationary phases) as well as the increased pressure to feed the hatched larva and then new adults (raiding phases).