How does a colony of several thousand ants coordinate its actions without any “leader”? The answer lies in two fascinating mechanisms: pheromones and trophallaxis. A dive into the language of ants.
Pheromones: a chemical alphabet
Pheromones are chemical molecules released by ants to communicate. Each message has a specific molecule:
- Trail pheromone: laid on the ground by foragers to mark a path to food
- Alarm pheromone: released when there is danger, mobilising nearby workers
- Recognition pheromone: lets workers of the same colony recognise one another
- Recruitment pheromone: calls for help with a task (carrying a large prey item, for example)
- Royal pheromone: released by the queen, signalling her presence and inhibiting egg-laying by workers
A single ant can produce more than 10 to 20 different pheromones, each with a precise meaning.
When an ant carries food back to the nest, it lays a trail pheromone along its path. If other ants follow that path and also find food, they reinforce the trail with their own pheromone. That’s why you see lines of workers always following the same route: it’s a chemical consensus.
The producing and receiving organs
Pheromones are produced by various glands: the mandibular gland, Dufour’s gland, the postpharyngeal gland, the venom gland. Each gland produces specific pheromones.
Pheromones are detected by the antennae, the ants’ extraordinary sensory organs. An ant antenna detects molecules at concentrations of a few molecules per million, a sensitivity 10,000 times greater than the human nose.
Trophallaxis: the mouth-to-mouth exchange
Trophallaxis is the exchange of nutritive and chemical fluid between two ants, mouth to mouth. It’s one of the most important mechanisms of a colony’s social cohesion.
When a forager brings back nectar or honeydew, it doesn’t eat it alone. It stores the liquid in its social crop (a separate stomach) and shares it with the other workers on return. A single trophallaxis can last from 5 seconds to several minutes.
Functions of trophallaxis
- Feed the ants that don’t go out (queen, young workers, nurses)
- Share pheromones and create a unique colony “scent signature”
- Synchronise the rhythms of the colony
- Spread information (presence of food, danger, health status)
- Heal: some sick ants receive antimicrobial compounds this way
Every ant colony has its own unique “scent”, a blend of pheromones shared through trophallaxis. A foreign worker introduced into a colony is immediately detected and killed, unless it manages to mimic (chemically or by camouflage) the local signature.
Beyond pheromones: sounds and vibrations
Ants also use other channels:
- Stridulation: some species produce a high-pitched sound by rubbing their abdomen, audible to nearby ants and even to the human ear up close
- Substrate vibrations: transmitted and perceived through the legs
- Antennal touch: a genuine tactile language between individuals that meet
A collective intelligence
No single ant is very intelligent on its own. No leader, no overall plan, no “complex” communication in the human sense. And yet, through simple chemical interactions multiplied by thousands of individuals, a collective intelligence emerges, capable of:
- Building complex nests
- Optimising foraging routes
- Regulating nest temperature and humidity
- Dividing labour efficiently
- Adapting to changes in the environment
It’s this phenomenon, emergence, that still fascinates researchers today and inspires artificial-intelligence algorithms.
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