What Is So Interesting About The Behavior Of Lemon Ants?

The Amazon rainforest in Loreto, Peru, where lemon ants can be found.
The Amazon rainforest in Loreto, Peru, where lemon ants can be found.

Lemon ants are small ant species scientifically known as Myrmelachista schumanni and are found in the Amazonian rainforests of Latin America. Like all ant species, lemon ants are social animals, and they live in organized colonies which are headed by a dominant queen, whose primary role is laying eggs. There exists little distinction in the physical traits of lemon ants. However, the behavior of these ants makes them quite interesting and have been studied by scientists for many years. Lemon ants live in and around Duroia hirstula, a tree species that are also native to the rainforests of Latin America. Lemon ants are known for attacking any other plant species attempting to grow around Duroia hirstula trees by injecting formic acid into the plant stems and leaves. After 24 hours, these plants die off, leaving patches of forests in which Duroia hirstula trees are dominant. These patches of forests are locally referred to as devil’s gardens. The largest devil’s garden observed is estimated to be over 800 years old and occupies an area of 1,300 square meters and is made up of 328 trees. However, in most instances in these devil’s gardens, a few plants species live close to the Duroia hirstula and are not attacked by the lemon ants, and these include the Tococa guianensis, Clidemia heterophylla, and the Cordia nodosa.

Myrmelachista schumanni: The Lemon Ants

Myrmelachista schumanni is the scientific name of lemon ants, an ant species which is found in the rainforests of South America. Currently, there are only one known subspecies of the lemon ant, officially known as the Myrmelachista schumanni cordincola. The lemon ant is found in large colonies in Venezuela, Santa Cruz, Bolivia, Ecuador, Peru, Colombia, and Brazil and the species is usually found in regions with an average elevation of 350 meters. The habitat in which lemon ants are commonly found is within second growth rainforests. The ant species is named the “lemon ant” due to its chemical defensive mechanism whereby when attacked, the ant releases lemon-tasting chemicals which act as pheromones, warning other individuals. The chemical which is known as formic acid also possesses a citrus odor.

Duroia hirstula: Trees That Form The Devil's Garden

The Duroia hirstula is the binomial name of a large tree species found in the rainforests of Central America and South America. The Duroia hirstula species is a constituent of the larger Duroia genus which is made up of 37 different species. All members of the Duroia genus are known for allelopathy, the process in which a plant inhibits the growth of surrounding vegetation through the use of biochemicals. Trees in the genus are known for possessing growth inhibitors in their root systems which include duroin and tetracyclic iridoid lactone. Trees of the Duroia genus release the growth inhibitor toxins to the surrounding vegetation, preventing them from growing. In Duroia hirstula, the process of allelopathy is also boosted by neurotoxins released by the lemon ant.

Ancient Beliefs

Ancient people who inhabited the rainforests of Latin America believed that the occurrence of the Duroia hirstula as the sole plant species in a region was the work of an evil spirit known as “Chullachaki.” The evil spirit, whose description was a short and ugly mythical beast, was believed to inhabit these unique patches of forest with Duroia hirstula trees and therefore these patches of forest were known as devil’s gardens. However, recent research conducted by scientists led by Stanford University’s Professor Deborah Gordon established that main cause for the phenomenal was a mutual relationship between the Duroia hirstula tree and the lemon ant.

What Research Says?

Researchers conducted a study in the rainforests of Peru, aimed at explaining the existence of devil’s gardens. Another aim of the study was to establish the exact cause of the inhibition of surrounding vegetation in devil’s gardens from the two probable causes; the release of growth inhibition plumerias by the Duroia hirstula or attacks from the lemon ants through the selective destruction of other plant species. In the research, scientists planted cedar saplings in 10 different gardens selected the Amazon rainforest of Loreto. Some of the saplings were protected from the lemon ants while the rest were not protected. After some time, the team of scientists learned that the saplings which were protected against the lemon ants thrived, but those without protection from the ants were destroyed. Scientists were able to conclude that while the Duroia hirstula trees did inhibit surrounding growth through the release of growth inhibitors, the impact of the inhibitor to the vegetation was negligible. Scientists established the main cause for the dominance of Duroia hirstula trees in devil’s gardens as Myrmelachista schumanni ants (also known as lemon ants).

Mutualism Between Ants And The Tree

Both the Duroia hirstula trees and the lemon ants share a mutual relationship in which both species benefit from each other. While the tree does not require the lemon ant for its survival, the presence of lemon ants increases the growth of the tree. This relationship begins after the queen ant of the Myrmelachista schumanni species settles in a Duroia hirstula tree and establishes a new colony. As the colony grows, worker lemon ants proceed to attack all surrounding vegetation, injecting plants with formic acid which kills the plants. Once the worker ants, which are on constant patrol, identify a distinct plant species in the surrounding, they attack the plant in their hundreds, leaving the plant to die a slow death. Besides, the lemon ants also attack herbivorous insects which attempt to feed on the Duroia hirstula tree. The Duroia hirstula tree soon produces saplings which are also protected by the worker lemon ants. In exchange, the lemon ants acquire a nesting ground in the Duroia hirstula tree where they form a colony inside the tree’s domatia which is normally hollow. The tree also offers nutrition to the lemon ants in the form of extra-floral nectar or food bodies inside the tree.

The Downside Of Mutualism

While there are major positive effects of the mutual relationship shared between the Duroia hirstula tree and the lemon ant, scientists have also established detrimental effects of the relationship, particularly faced by the tree. As the colony of ants grows in size, it weakens the structure of the tree as the ants form hollow passages and chambers inside the tree.


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