These Ants Decorate Their Nests With the Heads of Their Enemies

The tiny Formica archboldi ant has the particular habit of beheading opponents who are much bigger than they are, and decorating their nests with these heads. But why do they do this grisly act?

Ants are fascinating creatures. For many years now we have known that the Formica archboldi ant can decapitate its opponents before depositing the heads in their nests. What is surprising is that they are often much smaller than their opponents. A recent study could shed light on why they perform this strange ritual.

A little ant with a powerful weapon

One of their favourite victims is the dreaded Odontomachus, also known as the trap-jaw ant, and yet these ants are much larger than they are, and they have enormous mandibles and a sharp stinger.

How can a small ant take on an Odontomachus? In a recent study published by Adrian Smith in the International Journal for the Study of Social Arthropods, he explained that it can gain the upper hand over this sizeable adversary by spraying it with acid.

Almost all ants in this family are able to spray acid, but they usually only resort to this when in extreme danger. Formica archboldi, however, does not hesitate to use this strategy as a way to attack. 'It just looks like they want to fight,' explains Adrian Smith.

A way to get their scent?

In his study, Adrian Smith tried to understand the relationship between Formica archboldi and its prey Odontomachus. By analysing the layers of odorous wax, also called cuticular hydrocarbons, produced by this ant, he found that they correspond to those of Odontomachus. He then hypothesised that they take the scent of their prey in order to gain an advantage in battle.

Then Adrian Smith came up with a second, even crazier hypothesis. To understand it, one must know that another ant, called Polyergus, is known to attack Formica archboldi colonies. Nicknamed 'slave-making ants,' they kidnap and brainwash their victims.

A defensive strategy?

The queen slave-making ant kills the queen from the Formica archboldi colony, then immerses herself in her bodily fluids to soak up her scent. Thanks to this, she can escape while retrieving eggs, which later hatch into ants that are in turn able to perform this manoeuvre.

To avoid these attacks by slave-making ants, the Formica archboldi could try to modify their own scent, by capturing that of the Odontomachus. According to Adrian Smith, this could be one of the reasons why these ants bring the heads of their enemies back into their nests. This strategy was initially thought to be warlike, but ultimately it could be defensive.

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