Some ant species are belligerent creatures that engage in warfare on a magnificent scale. COURTESY OF THE SMITHSONIAN MAGAZINE.
Every day, billions of soldiers fight on thousands of fronts in wars that have been going on for a 100 million years. In his book Adventures Among Ants, Smithsonian Institute associate researcher Mark Moffett claims these soldiers loot enemy homes, launch toxic attacks, employ suicide bombings and even cannibalize their enemies.
He is, of course, talking about ants.
Over 10 trillion in number, ants constitute over 20% of the planet’s animal biomass – much more than humans. The 16,000 ant species discovered have evolved to thrive in nearly every ecological niche, and arguably by the same method us humans have. They have learnt, in their billions, to collaborate with each other.
In their complex colonies, ants care for livestock, pursue agriculture and engage in symbiotic relationships with other species. But these extraordinarily adept critters have undertaken yet another activity one would think was quintessentially human. They engage in devastating warfare that results in millions of casualties around the globe everyday.
The Army Ant
The most aggressive and destructive of ants, army ants don’t construct any permanent nests. Instead, an army ant colony is incessantly on the move, raiding and pillaging other insect colonies and killing up to 500,000 animals a day, rather like a certain 13th-century Mongol nomadic tribe.
An army ant on its own is rather small, but a colony almost always wins every engagement with its prey by overwhelming it with superior numbers – the colony’s queen produces an astonishing 3 to 4 million eggs a month!
Like any professional army, these ants have specialized into distinct units that have specific tasks. The “worker” caste consists of small, usually blind sterile female ants. The “soldier” ants are larger and have stronger mandibles, and the older soldiers even have larger heads. The male “breeding” ants actually have wings, which they use to fly to a queen ant they want to mate with – sometimes, they breed with the queen in their own colony. The “queen” is the largest of the army ants, is blind and has an enlarged gaster (or tail).
Army ants are so dangerous and effective in their “raids” that many other ant species have evolved to simply panic and evacuate their nests. Yet others, like the Pheidole obtusospinosa, have evolved to have large block-like heads that they stick into the entrances of the underground tunnels they live in to prevent an army ant incursion.
But, unlike Genghis Khan, these nomadic ants never attack their own species, largely because male “breeding” army ants mate with the queens of other neighboring colonies, creating “alliances” of sorts.
But if you’re looking for more than bloodthirsty raiding, look no further than the empire-building Argentine ant. Like the army ant, the Argentine ant looks rather small and unimpressive; it lacks the deadly stingers and strong armour other ant species are equipped with. Yet, the Argentine ants have built an empire that spans continents, and in the defense of which, millions sacrifice their lives daily.
Their empire – technically a super-colony – stretches across California, Europe, Japan and Australia, making it the largest society on Earth. The super-colony is tied together by bonds of kinship between its constituent colonies, each of which consists of billions of ants.
The Argentine ant is native to the Paraná Delta in Argentina, where they compete viciously for resources with the native fire ants and army ants. Because of the intense competition, the Argentine ants have evolved to become extremely aggressive. But their aggression is not the only secret behind their empire.
Argentine ant colonies frequently branch out to form new colonies. These new colonies cooperate with and never attack the mother colony, and soon come to constitute a super-colony. Only a few of the 16,000 ant species ever form super-colonies. But this peaceful coexistence does not last as the ties of kinship become more diluted over successive generations. Daughter colonies, in the span of a few generations, fail to recognize the mother colony as related, and are free to attack it.
The army ant, the fire ant and the Argentine ant would have sustained their aggressively competitive equilibrium in the Paraná Delta, had it not been for human intervention.
In 1882, an Argentine ant queen was accidentally transported to Spain, and in 1891, another ant queen found herself aboard a ship headed to New Orleans. The ants were suddenly outside the reach of their natural competitors and found only easy prey not used to their aggression. With nothing to stop them, their population exploded, and since all these ants are all descended from just a few ant queens, they all recognize each other as kin. They expanded as one massive super-colony.
In California, they’ve completely overrun and replaced the native carpenter ant and disrupted the region’s fragile ecology. The Argentine ants spew toxic chemicals on their enemies before “washing over them” and pulling apart their limbs. They even tend to hordes of aphids – small sap-sucking insects – as cattle. The aphids suck the sap out of agricultural crops (they are pests) and secrete honeydew, which they offer to the Argentine ants for protection. The ants in turn prevent any aphid predator from disturbing their sap-sucking. The aphids flourish and kill the plants they live on.
In San Diego County, however, some Argentine ant colonies have seceded from the super-colony and a horrifying civil war is underway – there are over 30 million casualties a year. The fire ants from the Paraná Delta have also made landfall in Alabama, bringing with them their generational hatred of the Argentine ant. They have succeeded in pushing out the Argentine ant from the entire South-East United States, claiming it for themselves in an ages-long war that has now reached global proportions.
“War is the province of men,” Éomer told the fair Éowyn in the Lord of the Rings. Well, these ants might pick a quarrel over that.
Do you think war is “natural”? Do humans fight wars for the same reason ants do? Does that mean war is embedded in our very DNA? Let us know what you think in the comments below!