Army ants – Raiders of the wild world

Army ants (or driver ants) represent the pinnacle of insect carnivorous, predatory behavior. Both terms generally refer to ants that form huge colonies, but exhibit swarming behavior, always on the march in search of food. In the Americas, the term army ant is more widely used, while in Africa, the term, driver ants is applied instead. However, “army ants” is a broad term that most people now apply for these ants. Army ants in the New World generally belong to the genus Eciton, while Old World army ants generally belong to the genus Dorylus.

These ants are the stuff of legend, and driver ants are the only insects known to kill and devour (gasp) human beings! These ants can easily overpower small animals that are unable to flee in time, but their diet mainly composes other small anthropods and invertebrates. A typical colony generally has a fertile queen and workers, eggs and young, with total numbers of individuals ranging from tens of thousands to tens of millions (depending on species). There are NO kings or males in a colony; in ants, all the males die soon after mating. Their "nests" are temporary, which they build using their bodies called bivouacs, although for subterranean army ants, they do excavate simple chambers and tunnels below ground to house their young.

The Dorylus "safari ants"

Although Dorylus species are the ones that have earned army ants their infamous reputation, not all Dorylus are as aggressive or as vicious as made out to be, this mainly reserved for a few African species. Among all ants, I find these ants among the most interesting; I guess due to their infamous nomadic and predatory lifestyle.

All army ants have a definitive soldier caste (also called the major worker caste), with the solders being larger, having a larger head, and large pincer jaws. The only army ants I have personally come across thus far was Dorylus laevigatus, a species of South East Asia. Dorylus laevigatus is not a large, nor particularly aggressive ant, but maybe this is due to it being a subterranean army ant. You can see photos of many Dorylus species here.

For the record, there are basically two types of army ant; those that forage mainly above ground, and those that do so mainly below ground. So, army ants that hunt above ground tend to get attention, because they will attack any creature that gets in their way, whereas subterranean army ants hunt small soil dwelling creatures and are therefore, seen much less often. When foraging, scouts will lead a raiding column and when they come across prey, they release a pheromone signal that tells nearby ants to pounce on the prey. Once the target is "locked in", army ants relentlessly stream to the site without ever letting up.

Army ants frequently prey on termites, and raids on termite nests are commonplace, but they rarely make a concerted effort, enough to destroy an entire nest. These battles between army ants and termites are merciless and bloody, with a very high body bag count! Normally, army ants gain access into termite nests via the foraging tunnels used by the termite workers, or following in the wake of an aardvark or anteater digging up a mound. If the termites succeed in blocking up the tunnels, they can normally withstand an attack by the ants.

While we might think of army ants as fierce insect huns, the fact is, they are also preyed on by opportunistic predators (including other ants). It’s all a part of nature’s check and balance. Otherwise, all the lands where army ants occur would be overrun by them by now. Once more, you have to marvel at how nature balances everything up perfectly; the only ones screwing things up are us humans.