The Insane Biology of: Ant Colonies

Ants have a total population around 10,000 trillion individuals and when combined their total weight would be about the same as the weight of all human beings where in biomass and impact on ecosystems these small animals are arguably the most successful creatures to have ever lived having colonized almost every land mass on Earth.

Even though insects were among the first animals to colonize land where the first insects emerged around 400 million years ago, ants did not emerge until much later around 100 million years ago living among the dinosaurs and for a long time did not rule the landscape during the era of giant dragonflies, cockroaches and termites until 60 million years ago when they became the dominant insects.

The competitive edge that allowed ants to become a world dominant group is their highly developed colonial existence and specialized social structure where ant societies are broken up into two castes being a non-reproductive worker caste and a reproductive royal caste representing a fundamental organizational principle.

Over the course of her life a queen ant can lay up to 300 million eggs depending on the species of ant and the vast majority of these eggs hatch into dedicated worker ants being female ants whose lives are devoted to the queen’s welfare and reproductive activity where at any given time there are millions of worker ants maintaining the colony.

The queen is the only reproducing female of the entire colony and the colony exists to serve her and her alone where the birth of a colony begins with the birth of a queen establishing the foundational principle that all colony activity centers on supporting the queen’s reproductive success.

Surprisingly it is the ant workers themselves who ultimately decide the fate of their young choosing which worker caste they will develop into where larvae develop into different types of workers based largely on the nutrition they receive and those fed more insects than seeds are more likely to become larger individuals.

When the colony passes a certain size the queen lays special eggs that hatch into larger ants with wings being reproductive males and young queens where during a nuptial flight these winged ants take to the air and mate with each other after which the males die and the females drop to the ground, scrape off their wings and begin to search for a place to dig their nest but only around 1 in 500 new queens has a chance at success.

There can be many different types and many different sizes of workers even within a single colony where for leaf cutter ants the polymorphism that exists among the workers is extreme with the largest workers called soldiers defending the colony, while the medium-sized workers collect leaves, excavate tunnels or collect garbage, and the smallest workers raise the young and cultivate and farm fungus which is the only food source for the whole colony.

For years scientists knew that ants must have some way to talk to each other in order to organize their intricate societies but ants have poor vision and hearing so scientists knew that ant communication must work in a fundamentally different way to ours where it was a mystery for years until in 1962 leading entomologist E.O. Wilson began to crack the code of ant communication by discovering that De Four’s gland produces a trail pheromone.

When an African weaver ant worker encounters an enemy in her own territory she releases a mixture of four chemicals that not only convey a message but elicit a response from all other workers in her vicinity where the first tells the other ants to be alert, the next one tells them to search for the trouble, the next one tells them to come closer and bite anything in their path, and the final compound tells them to go nuts and attack.

Over time scientists have discovered over 20 different pheromones that ants use to communicate and by combining different signals ants have created a complex pheromonal language where African weaver ants in particular have the most sophisticated pheromone communication system ever studied in animals with some thoughts expressed by spreading pheromones on the ground combined with physical gestures and scientists believe that the combination of these signals very closely resembles syntax that we see in human language.

Weaver ants are a species of ant that do not live in or on the ground but in the trees and to keep their huge population safe there they construct their own housing by weaving branches and leaves together where if the gap is too large for a single row of ants to seal they perform an impressive acrobatic tactic by chaining their bodies together to form a living bridge with workers climbing down the bodies of others until the chain can reach the other leaf edge up to 10 workers long.

Worker ants die young and usually do not create offspring where their existence is sacrificial and they have no self-interest since certain ants have been found to suffer a death rate of six percent per hour when outside the nest due to fighting with neighboring colonies and on average each forager survives for only a week but during that time she manages to collect 20 times her own body weight in food for the colony all to support the group and ultimately the queen.

This unwavering loyalty to the queen and the self-sacrifice to her cause becomes more evident when a queen dies where logic would assume that when the queen dies the workers would raise another queen to replace her but this is not at all what the workers do since in most cases the colony fails to produce a royal successor and it declines until the last worker dies where they simply do nothing until there is no one left.

In the 1960s and 70s the conventional way of thinking about evolution was centered around genes and genes alone largely popularized by Dawkins book The Selfish Gene where it follows that the more two individuals are genetically related the more sense it makes for them to behave selflessly with each other and that altruistic group behavior comes down to each individual’s competitive desire to improve chances of their kin’s survival.

Some ant biologists like E.O. Wilson believed that selfish gene theory could not be the whole story since instincts from social species like ants go far beyond the urge to protect their immediate kin where the group must also have a role in evolution whether or not the group members are related to each other and this idea gave rise to the theory of multi-level or group selection where natural selection acts at the level of the group instead of at the more conventional level of the individual.

The idea of the superorganism is one that has been debated for decades with ants where it is the idea that the colony is the organism in which the queen is the reproductive organ, the workers are the supporting brain, heart and gut, and the exchange of food among the workers is like the circulation of blood where the most advanced ant societies like weaver ants, driver ants or leaf cutter ants fall into this category in which their workers do not compete amongst themselves at all and do not reproduce outside of royalty.