The harmless red ants that live in the forests of Florida turned out to be secret "bounty hunters". They kill larger ants with acid spits and collect their skulls in their nests, writes a naturalist who published an article in Insectes Sociaux.
“Back in 1958, when these ants were discovered, scientists noticed something unusual. Their nests and their surroundings were littered with the severed heads of giant odontomach ants, feared and respected even by spiders. No one knew where they came from in the colonies of their humble red-haired cousins,”says Adrian Smith of the University of North Carolina at Raleigh (USA).
Farmers, Raiders and Slaveholders
Ants and other social insects such as bees and termites date back to the time of the dinosaurs, and over the next hundreds of millions of years of evolution, they have developed a wide variety of and often extravagant lifestyles.
For example, today there are about two hundred species of "farmer" ants on Earth, growing the same mushrooms and feeding on their fruit bodies for many millions of years. Many of their cousins living in the rainforests of the Amazon have completely abandoned permanent colonies and switched to a "nomadic" lifestyle, while others have learned to capture other people's anthills and turn their inhabitants into their slaves.
Smith uncovered the secret of one of these bizarre species of these insects while observing colonies of common ginger ants (Formica archboldi) living in the forests of Florida and other southern regions of the United States.
Initially, as the scientist notes, he was not interested in the mystery of why these ants collect the skulls of larger congeners, but in what chemical signals they use to communicate with their own kind and representatives of other species.
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Much to his surprise, Florida red ants produced a very different set of odors than the rest of the Formica genus. In most cases, their pheromones were virtually indistinguishable from the volatiles produced by the odontomachus ants, whose skulls are often found in their nests.
This is a very strange coincidence from an evolutionary point of view. As a rule, insects use these signals in order to distinguish representatives of their own species from other ants, rather than trying to resemble each other, unless one of them leads a parasitic lifestyle.
Moreover, given that odontomachs have long been considered one of the most dangerous and ferocious predatory ants in America, it would be logical to assume that red ants would have to be very different from them in order to avoid collisions with these giants.
Hidden hunters
This led Smith to a paradoxical idea - Formica archboldi could purposefully hunt these giants, using their smell as one of the means of "camouflage". Accordingly, their skulls should not be random "decorations" of the colonies of red ants, but the traces of the "meals" of the latter.
He tested this idea by catching several odontomachs and planting them in a small laboratory colony of Florida red ants and other members of the Formica genus. Subsequent observations helped him uncover the secret and very powerful weapon of the Formica archboldi.
It turned out that these ants can really kill odontomachs by approaching them and shooting them in the "face" with a jet of acid. One such shot, as shown by observations with a high-speed camera, was enough to seriously injure a predatory ant, and completely paralyze it in 70% of cases.
When this happened, the author of the "shot" transferred his victim to the colony, where it was stripped of its head and eaten by the hunter's relatives the next day.
Interestingly, the closest relatives of Formica archboldi did not behave in this way, but their acid also caused paralysis in odontomachs. This suggests that Florida red ants evolved from "omnivorous" insects into highly specialized "bounty hunters", whose main food source was some of the most dangerous invertebrates in the forest.
