The Fantastical Lives of Ants

In the Cretaceous period, when dinosaurs rumbled over the earth and plants first began to bloom, the first ants emerged. They had evolved from Parasialids (insects most like sawflies dating back to the Permian) and would have had to develop parasitoidism, a wasp-waist, a sting, and eusocial societies before anything recognisable to us as an ant could be found 200 million years later.

Since then, ants have traversed the globe and made their homes on every continent apart from Antarctica. With an estimated 13,000 to 16,000 living species described and 30,000 predicted to be found, they are a highly speciose family that have adapted to every terrestrial habitat. Given the vast numbers of ants found in some ant colonies, it has been suggested that there are 10, 000, 000, 000, 000, 000 (10 quadrillion) ants alive at any one time. Their global distribution is, however, somewhat skewed towards warmer climates, with ant species diversity and density being highest in the tropics, where ants and termites make up a third of all animal biomass.

These extraordinary numbers reflect ants' successful colonisation of their local environments and has sometimes given rise to some truly bizarre adaptations. And, as ants can be considered a dominant group of terrestrial invertebrates, it would make sense for them to exploit other ants.

Slave-making Ants

It is a labour-intensive job to create a new colony and maintain its worker population. The queen must lay thousands of eggs, which the workers then have to keep clear of pathogens and parasites, and then feed and nurture the issuing brood. It can take months for a colony to replenish its numbers following an attack by a large predator or a competing ant colony. Some ants have evolved the behaviour dulosis (commonly known as slave-making) to circumvent these problems. They simply send out a raiding party to other nearby ant nests, slaughter the adults and kidnap their brood. This brood will be returned to the nest of the slave-making colony, where they will become integrated. These so-called slave ants will then perform the colony functions of feeding and nest maintenance as the raiders have become too specialised to perform these functions themselves. This raiding behaviour can be observed in one of the UK's Wood Ant species Formica sanguinea, parasitising its near-relatives Formica fusca and Formica lemani. Raids by F. sanguinea can include over 1,000 raiders forming a column around 12 metres long and 50 cm wide. Charles Darwin was unable to explain this behaviour, commenting: "By what steps the instinct of F. sanguinea originated I will not pretend to conjecture," in 'On the Origin of the Species by Means of Natural Selection'.

However, this is not necessarily a done deal, sometimes, the enslaved ants rebel. It has been observed that the captured workers attack some of the brood of their kidnappers either by ripping apart pupae and eating the chunks, or by dumping them in the corner of a chamber and leaving them untended so that they succumb to moulds. In some situations, up to 80% of developing queens and 60% of young workers can be killed by these slave nursemaids. It is thought that this is to increase the survival chances of the ants in nearby colonies that survived previous attacks (Pamminger, T. et al., 2014) .


"I warn you, child... if I lose my temper, you lose your head! ..."

Another form of social parasitism in ants is known as inquilinism. This isn't slave-making per se, but more the co-opting of a nest and colony by the queen of a closely related species. This tactic uses guile and deception rather than the brute-force tactics carried out by slave-makers. A parasitic queen ant will enter the nest of her host species, kill the incumbent queen, and take her place. The strategy of these parasitic queens is to mimic the host queen so that the rest of the colony don't notice that she's a usurper, but first, she must make it into the nest. She does this by catching sentries near the nest entrance, dispatching them, and then effectively taking on the scent of the colony by rubbing herself against their corpses. This gets her in the door, where she will cautiously hang around until she has properly taken on more of the colony odour and has become indistinguishable from her unsuspecting hosts. Now she proceeds to the chamber that houses the queen, where she will again wait, occasionally touching the queen to acquire her specific odour. Once the workers are unable to differentiate between the two queens, the parasitic queen strikes. Thereafter there are two possible strategies employed by the newly actualised queen. Depending on the species, she can either become a 'temporary social parasite' or a 'permanent social parasite'.

In the case of permanent social parasitism, the queen doesn't produce any workers and comfortably stays in the nest and produces more queens and males that will disperse, mate and then continue the cycle until the colony dies. Temporary social parasites on the other hand, will produce workers and in this way, will eventually replace all the host workers in the colony.

In Britain, Myrmica scabrinodis and Myrmica sabuleti are sometimes parasitised by queens of Myrmica karavajevi which co-exists with the resident queen in the host colony. Recent research (Casacci, L.P. et al., 2021)  has revealed that the parasitic queen uses a combination of chemical cues and vibroacoustic signals near-perfectly imitating those of the host queen, eliciting the same levels of attention from host workers.

Royal Frenemies

A fairly common form of colony foundation in ants is known as pleiometrosis. This involves the co-founding of a new nest by several newly mated foundress queens. By clubbing together, they can establish a larger colony faster to better take advantage of available resources and defend the nest. What is curious about this behaviour is that the foundress queens, though of the same species, are often unrelated. As the colony becomes functional, there are several possible outcomes for these queens: they can continue to live in the same nest peacefully contributing to the growth of the colony; or they can come into conflict with each other, fighting amongst themselves for dominance with the victorious queen either killing off her competitors or banishing them from the nest. This behaviour is common in the Yellow Meadow Ant (Lasius flavus) with, in most cases, a single victorious queen surrounded by the bodies of her rivals.

It's an old story

By all accounts, it isn't easy trying to establish a new colony and defend a territory, so ants have employed a number of different tactics to try and get an advantage over their competitors. By taking advantage of their eusocial behaviour, ants are able to bolster their numbers by raiding workers from other colonies, they are able to co-opt entire existing colonies by removing the resident queen, they are able to co-exist with unrelated adoptive sisters in peace, or they can fight for overall control of the colony with their co-foundresses banished or beheaded. This is like Game of Thrones playing itself out in miniature all over the world, but on a scale that we can't completely comprehend with more than 400 socially parasitic species in six ant subfamilies recorded. And it has been going on for a long time – emerging 17 million years ago in Formica ants (Borowiec, M. et al. 2021)  - and having evolved at least 60 times in ants.

So, it seems that ant colonies evolved many behaviours that Cersei Lannister summed up nicely: "When you play the game of thrones, you win or you die."


If you would like to learn more about ants and their fascinating life histories, why not sign up to one of our ‘Learn to Love Ants’ courses, running in both the West Midlands and the South East. We also have some opportunities upcoming to allow you to work on your ant identification skills. More details can be found here.