Scientists found ants have been running tiny 'Dairy Farms' for 35 million years, and the sweet reward explains why

Ants are often admired for their teamwork and organization, but scientists say one of their most remarkable achievements has been happening quietly for millions of years. Long before humans began keeping livestock, certain ants had already mastered a farming system of their own.

According to a research review published in the journal Current Biology by researchers Aniek B.F. Ivens and Daniel J.C. Kronauer, ants have spent at least 35 million years tending aphids in a mutually beneficial partnership. The study explains how this ancient relationship has endured through evolution and why both species continue to depend on one another.

Why do ants keep aphids like livestock?

To most people, aphids are little more than tiny insects feeding on plants. To ants, however, they are something far more valuable.

According to the Current Biology research review, ants "farm" aphids in a relationship known as trophobiosis, where food is exchanged for protection. The aphids act as the "trophobionts," producing a sugary liquid called honeydew, while the ants provide services that help the insects survive.

Honeydew is produced after aphids feed on nutrient-rich plant phloem. Although aphids consume large amounts of sap, their digestive system leaves plenty of sugars, amino acids, organic acids and salts in their waste. For ants, that sweet liquid becomes a reliable food source.

Rather than waiting for the droplets to appear naturally, ants gently tap an aphid's abdomen with their antennae. The aphid immediately releases a drop of honeydew, which the ants consume. In addition to collecting honeydew, ants occasionally eat some of the younger aphids or those producing less honeydew, making the colony both a source of carbohydrates and protein.

This farming system works because aphids remain in stable colonies for much of their lives, giving nearby ant colonies a dependable food supply.

How has this unusual partnership survived for millions of years?

The arrangement is far from one-sided. Aphids are slow-moving, defenseless insects that face constant threats from predators and parasitoid wasps. Left alone, they are easy prey. Ants change that equation completely.

The research explains that ants aggressively defend their aphid colonies by attacking predators such as ladybirds and hoverflies. Parasitoid wasps searching for aphids are also driven away, making it much harder for them to reproduce inside the insects.

When danger becomes more serious, ants go even further. If a nest is disturbed, they quickly pick up their aphids and carry them to safer locations deeper underground.

The benefits do not end with protection. Ants also help keep aphid colonies healthy by removing excess honeydew before it encourages sooty mold growth. Sick or dead aphids are removed as well, helping reduce the spread of disease. In some underground colonies, ants even build protective chambers around plant roots, giving aphids direct access to their preferred food source while sheltering them inside the nest.

Researchers describe this exchange as a classic example of mutualism, where both species receive clear benefits. Ants gain a dependable food supply, while aphids receive protection, cleaning and, in some cases, housing.

How has this partnership evolved over millions of years?

According to the Current Biology research review by Aniek B.F. Ivens and Daniel J.C. Kronauer, fossil evidence preserved in amber shows that ants were already tending aphids at least 35 million years ago. Researchers believe the partnership may be even older, possibly dating back as far as the Cretaceous period, around 75 million years ago.

Today, this remarkable relationship is found across much of the world, from temperate regions to tropical forests. Of the roughly 4,000 known aphid species, about one-quarter are attended by ants. The widespread nature of these interactions suggests they evolved independently many times, making them one of nature's most successful examples of cooperation.

Not every ant and aphid partnership works in the same way. Some are facultative, meaning both species benefit but can survive independently. Others are obligate, where each partner has become so closely adapted to the other that survival without the relationship becomes difficult.



Above ground, aphids live on leaves and branches while ants regularly travel between their nest and the aphid colony. These partnerships are usually temporary, lasting only through a growing season.

Underground, however, the relationship is often much stronger. Aphids feed on plant roots inside or near ant nests, and many no longer produce winged forms or reproduce sexually. Instead, they remain protected within the colony for years, creating a far more stable partnership.

How do ants and aphids communicate?

The success of this tiny farming system depends on constant communication. The research explains that ants and aphids rely on chemical signals, known as semiochemicals, as well as substances found in honeydew to recognize and respond to one another.

Aphids release alarm pheromones when threatened. Those signals not only warn nearby aphids but also alert their ant protectors, prompting them to rush in and defend the colony.

Aphids also respond to ant trail pheromones. In one example highlighted in the review, cotton aphids exposed to trail pheromones from the red imported fire ant showed lower dispersal and increased reproduction, helping strengthen the partnership.

Ants, meanwhile, recognize suitable aphids through the chemical compounds present on their outer surface. Some aphid species have evolved remarkable adaptations to improve the relationship, while others have taken advantage of it in surprising ways. The review describes one aphid species that mimics the chemical profile of ant larvae, allowing it to enter ant colonies unnoticed before feeding on the larvae.

Over millions of years, both partners have developed behaviors and physical traits that make the relationship more efficient, from specialized honeydew-producing structures in aphids to highly organized defensive responses in ants.

What can ant farming teach scientists today?

The research suggests this ancient partnership offers valuable lessons about evolution, cooperation and ecology. Because ants protect aphids so effectively, aphid populations can grow much larger than they otherwise would. This can increase pressure on plants, as aphids feed on plant sap and also spread plant diseases. At the same time, ants often drive away other plant-eating insects, meaning their presence can sometimes reduce damage from different herbivores.

These interactions ripple through entire ecosystems, influencing predators, parasitoid wasps, microorganisms and plant communities.

The findings are also important for agriculture. Several aphid species that benefit from ant protection are among the world's most damaging crop pests. Their partnership with ants can reduce the effectiveness of natural pest-control agents such as ladybirds and parasitoid wasps, making crop management more difficult.



Researchers also point to another fascinating area of study: the microbiomes of ants and aphids. Bacteria living inside aphids can influence the composition of honeydew, while bacteria inside ants may help them process the sugary food they collect. Scientists believe these microscopic partners may also play a role in maintaining the ancient relationship.

The review notes that ants do not limit their farming activities to aphids. They also tend insects such as mealybugs, soft scale insects and treehoppers, collecting honeydew in much the same way. In some species, young queens even carry these insects with them when founding new colonies, ensuring the farming partnership continues into the next generation.

More than 35 million years after it first appeared in the fossil record, this remarkable alliance remains one of nature's clearest examples of mutual benefit. As highlighted in the Current Biology research review, ants have built an agricultural system based not on crops, but on cooperation, proving that one of Earth's oldest farming traditions belongs to insects no bigger than a fingernail.

FAQs

Why do ants protect aphids?

Ants protect aphids because they feed on the honeydew the insects produce, making the partnership beneficial for both species.

How old is the ant-aphid farming relationship?

Research suggests ants have been tending aphids for at least 35 million years, with the partnership possibly dating back even earlier.