Leaf Cutter Ants: The Farming Insects

“Fertilizer” A male adult worker ant brings back a leaf that will be used to grow a fungus fed to the larvae.

Whether walking through the forest or through the middle of a city, the leaf cutter ant is a common site in Costa Rica.
You think humans are advanced? These little guys have been growing their own crop for probably millions of years. In their “gardens” below the soils surface, mature adults shoulder a perpetual supply of clipped leaves to a collection of fungus. Ant larvae are weaned on the fungus until they reach adulthood.
But, like our crops, the fungus requires more input than just feed. The rodents and pests of the ant farm equivocate to parasites, mites, molds all trying to feed on their precious harvest. The disposal of these pests is a risky process as some parasites can infect the ants and cause their heads to explode, so the task is left to the elderly, who are more dispensable. These “grandpas” are charged with constantly shifting material from the crop to a waste heap. They even contain antibiotics in their stomachs that help keep the fungus healthy.
By the way, did I mention that the leaves these ants are carrying can be 10 times their weight!
When mature females have an inkling to start their own colony, they start by having sex, a lot. She needs to collect 300 million sperm before flying off in search of suitable caverns and when her 50 million larvae are born, she is ready. Queens contain a pocket in their oral cavity where they store the harvested fungi which they begin growing as soon as the new colony is formed.
While excellent farmers, these ants can be very destructive to human cultivation activities. One colony can wipe out an entire acre of crop and reduce the amount of fruiting in trees. For this reason, many farmers use pesticides and, in cities like Heredia, the trunk of the trees are painted to deter the ants from climbing them. Interestingly, the ants seem to sense the effects of pesticide laden leaves on their crop and will stop using a particular tree in these cases.

“Deterrent” Trees in Heredia painted to keep ants from climbing and taking the leaves.

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