The ant is a tiny creature, seen all around us, but how often do we think about it? In nature it is hard to match the ant as an example of hard work, punctuality, unity and discipline. Ants do not fall into want and know no famine; millions of them are skilled at finding their own food.

A recent research report by scientists published in The Guardian says there are about 14,000 species of ant in the world. Some tropical species use chemicals produced in their own bodies to drive harmful insects out of crop fields, preventing pollution. So farmers need not spray poison to stop pests attacking their crops; these ants could be an alternative.

Meanwhile, in the Pacific island nation of Fiji, one kind of ant behaves just like a tiny farmer: it carefully sows seeds and then fertilises them. A team of researchers at the University of Munich in Germany reported this recently. Their study, published in the journal Nature Plants, says ants named Philidris nagasau farm fungus to supply their own food. The ants defecate right there, so the seedlings get the fertiliser they need to raise soil fertility.

We know that in the past states were built by winning wars, and that people of ancient times made slaves of other people. Did we know that among ants too there are wars to seize states? An ant state has a queen and an army, each soldier skilled in guerrilla fighting and in climbing high on one another's shoulders. There are also skilled workers and good citizens, and even slavery, achieved by the same means: war.

Everyone knows that beehives and ant nests have worker bees and worker ants alongside the queen. Usually the queen and workers in a nest or colony are of the same species. But ants of the Polyergus species cannot gather food, cannot feed their young and cannot even keep their own homes clean. They need worker ants and soldier ants. So, to collect skilled workers, slaves and skilled soldiers, they raid the kingdoms of Formica ants in groups.

Sometimes they travel more than 150 metres to attack a Formica state. The attacking Polyergus drive away the Formica queen and workers and carry the pupae back to their own state. Other slave ants look after these pupae, and once they hatch they take on the colony's work, in a word the many tasks of the state. When the ant population of a state grows, the Formica workers, soldiers and slaves carry about 2,000 Polyergus pupae and the queen to a new nest.

Researchers say the events before a colony is seized all happen underground, so they are very hard to observe. So Howard, a researcher at the American Museum of Natural History in New York, built transparent nests with his graduate students and observed the process experimentally. Howard and his students also tried to find the reason for this significant brainwashing of Formica ants.

They noticed that a Formica queen was killed in cold blood and the body was immediately brought before the Polyergus queen. The Polyergus queen at once began biting the lifeless queen, and the biting and licking went on for 25 minutes. As soon as it finished, the worker ants busied themselves caring for their new queen. From this the researchers concluded that by licking the Formica queen's body fluids as she kills her, the Polyergus queen takes in the Formica queen's chemicals. Absorbing these chemicals is why the Formica workers so quickly become her obedient followers.

To test whether this was right, the researchers ran another experiment. They removed a Formica queen from her nest and put a Polyergus queen in her place. This time the workers behaved quite differently: they waged a tireless, long war against the Polyergus queen and in the end managed to kill her.

A Polyergus queen alone is enough to kill a Formica queen. Once the Formica queen is dead, the Formica workers accept the invading Polyergus queen as their own. When a new queen is born in a colony, she joins the other workers on slave raids. As the advance party moves on, the new queen suddenly stops and, by releasing pheromone (a chemical secreted to attract the opposite sex) from her jaws, lures a male ant to mate. After mating she sheds her wings, then leaves her companions and sets off in search of a Formica nest.

Having found one, she moves very quickly to kill the queen, overcoming every obstacle to reach her. To kill the queen she uses her powerful jaws and a chemical secreted by the Dufour's gland near her abdomen. After clearing the workers' resistance, the Polyergus queen keeps biting the Formica queen's head, thorax and abdomen, licking her wounds as she bites.

The moment the Formica queen dies, the situation in the ant state changes. The Formica workers approach the new queen calmly, as if spellbound, and care for her just as they cared for the old one. The Polyergus queen then gathers the scattered pupae into a heap and stands over them like a victor at a coronation. This is how an ant colony is seized and a state conquered.

Although a Polyergus state has one queen, a full Formica state has been seen with several, up to 25. The researchers say they had long been curious about what happens when a Formica colony ruled by many queens is attacked. Surprisingly, the number of Formica queens had no effect on the Polyergus queen's raid. After killing the first Formica queen she showed no urgency: waiting hours or days, she methodically killed the other Formica queens, sometimes taking several weeks to remove the last trace of resistance.

These raids do not always end in victory. Sometimes Formica workers attack the Polyergus queen and tear her to pieces. The Polyergus queen also has another tactic. Because Polyergus and Formica queens happen to mate at the same time, they meet outside the nest too, and the Polyergus queen then easily kills the Formica queen. Having absorbed the Formica queen's chemicals, she can enter the Formica state without hindrance and carry on the killing unopposed.

The researchers say ants do not believe only in slaughter; they have principles. A Polyergus queen released in front of a Formica queen that has just mated for the first time does not kill her. She is interested in killing only a Formica queen whose offspring are grown enough and skilled at work and care.

According to biologists, Polyergus ants attack only those queens that have passed at least five months since fertilisation, meaning an important chemical change takes place in Formica ants in that time. The researchers noticed that Polyergus can force various Formica species into servitude, but they are less successful with unfamiliar Formica than with familiar ones.

Because Formica ants breed so prolifically, they have not disappeared from the earth despite these attacks. Why older enslaved Formica do not return to their kin is another pressing question for researchers. It is probably a matter of habit, because newly hatched Formica regard the state newly seized by Polyergus as their own, and chemical stimulation plays a bigger part in this habit than sight or sound. Some prefer to say "workers or citizens" rather than "slavery". Scientists say such a relationship requires host and parasite to be animals with similar traits. The Formica supply food, improve the nest and fight wars for the Polyergus state, just as free Formica workers or citizens do in their own colonies or states.

The writer is a science writer and researcher, and an MPhil scholar in the Faculty of Social Sciences, University of Dhaka.

Source: Jagonews24. First published in Bengali on The Agro News.