Among the ants we find some of the examples of the most complex societies known among animals . Their colonies are organized at a level called eusociality , thanks to an extraordinary caste system, biologically determined with specific functions. They remind us of our body and the differentiation system of our cells, with the ultimate goal of making the organism work, and we find clear parallels between both cases that can sustain an analogy .
There are ants that are in charge of looking for food and bringing it to the colony, just as we have organs that help us recognize food and take it to our mouths. Others dedicate themselves to making and preparing that food and driving it around the anthill, to feed the rest of the ants, in a kind of circulatory system that distributes the nutrients. Others are in charge of defending the anthill from external aggressions, as if it were an immune system. And of course, there are castes of ants, sexed, whose function is to provide ants capable of founding, in the future, new anthills, in a parallelism to how our gonads produce the cells that, with luck and if the optimal conditions are met, will give room for new people.
To reach the level of coordination that the cells of a human body—or of any animal —have, several communication systems are necessary . In our body, this role is covered by various forms of chemical signaling, such as hormones or cytokines, and by the nervous system. And if ants really have such a complex level of organization, analogous to that of a living organism , they also undoubtedly require one or more communication systems between individuals.
How do ants communicate?
Just as humans use different forms of communication —a mime, a pianist, a writer or an announcer does not communicate in the same way—, ants have different means of transmitting messages, and the same species can use several forms of communication simultaneously. Some species have an excellent sense of sight, using visual cues ; many use touch , and in some cases there is also communication by acoustic signals . However, all these forms are overshadowed by the most sophisticated communication system of all: the use of pheromones .
In anthill tunnels, semi- volatile chemicals can permeate the air and walls; substances that the ants capture with special receptors located on the antennae and that they recognize thanks to the fact that up to 12% of the total volume of their brain is dedicated to it.
Among the pheromones that an ant emits, we find mainly two types . One permeates the ant’s body permanently and is what identifies the ant in its colony . The entomologist Vidal Cordero, from the CSIC, uses the analogy of these identity pheromones as a kind of chemical DNI that allows the members of the anthill to recognize their congeners and identify possible impostors.
The second type includes the pheromones that the ant can emit at will , through different glands in its body. These usually have different meanings depending on their composition, the context in which they are found and the concentration of the different chemical products that contain it. Sometimes , they even emit substances that generate reactions on other living beings , acting on their behavior; they are called semiochemicals .
Following the pheromone trail
Many ants have, at the far end of their abdomen, a gland that secretes track pheromones . When an ant finds a path that is interesting to its colony—such as the route to follow to reach a food source—it will drag its abdomen along the ground , spraying the path with these pheromones . In this way, other ants will find their way. If the destination is really interesting, more and more ants will mark the trail, and the path will become more important for the anthill.
Runway pheromones contain a large number of chemicals that differ greatly in their ability to persist . Very volatile pheromones disappear quickly, and if no animal renews them, they are lost forever; Low volatile pheromones last over time marking old routes that are no longer used. Thus, an ant is able to recognize whether a pheromonal track is new or old . It is a way of preserving a path in memory. As the ants do not have a brain adapted to maintain this knowledge in the long term, they “write” it on the ground with their “ink” of pheromones.
Where once there was food, there may be again in the future, so it is not uncommon for some scouts to retrace old trails to check for food or prey again.
The “voice” of alarm
Another type of pheromones that ants can emit are alarm pheromones. With glands on the head and abdomen, these pheromones are released at will when they perceive danger or suffer aggression .
These are very volatile pheromones , which spread rapidly in the vicinity of the emitting ant, and last for a very short time. When an ant receives an alarm signal, it in turn reacts by emitting a new alarm, creating a chain reaction in all the ants in the vicinity.
Before an alarm, the ants can react in different ways . The most aggressive forms, or “soldier”, usually come to attack the enemy, in defense of the colony , while the workers more specialized in other tasks tend to flee.
A peculiar behavior related to alarm systems is that found in the species Megaponera analis , ants that frequently attack termite colonies . When, during an incursion, an ant is injured, it emits pheromonal signals analogous to what we understand by “pain”. A specific communication that alerts your colleagues of your state of health . This provokes rescue behavior in her partners; They transport it to the colony and care for it, exuding antimicrobial substances in their saliva and licking their wounds. It is estimated that, under these circumstances, treatment of injured ants can reduce mortality by up to 70%. % .
This article has been reviewed and approved by José Manuel Vidal Cordero,
entomologist at the Doñana Biological Station (CSIC)
David Morgan, E. 2009. Trail pheromones of ants. Physiological Entomology, 34(1), 1-17.
DOI: 10.1111/j.1365-3032.2008.00658.xFrank, E. T. et al. 2018. Wound treatment and selective help in a termite-hunting ant. Proceedings of the Royal Society B: Biological Sciences, 285(1872), 20172457. DOI: 10.1098/rspb.2017.2457Jackson, D. E. et al. 2006. Communication in ants. Current Biology, 16(15), R570-R574.
DOI: 10.1016/j.cub.2006.07.015Vidal Cordero, J. M. 2021. Las hormigas. CSIC, Catarata.