Leafcutter ants- Air conditioned farmers

Leaf cutter ants are among the most recognisable and famous groups of ants. Countless people have seen these species in zoos and in documentaries. This post will focus on Atta and Acromyrmex for the sake of simplicity and sanity. There are 46 other ant genera that grow fungus for food so I can’t cover them all here. They will get some posts of their own. Ants and fungus forever!

Leaf cutter ants are from the genera Atta and Acromyrmex. There are a total of 68 species in these genera and they are all found in the Americas. They are among the most complex societies on earth and there is much more to them than meets the eye. As a rule of thumb, Atta species are larger and live in larger colonies with up to 8 million individuals per nest. Not the largest but are much more complex. Atta species also have 6 spines on their thorax while Acromyrmex have 8. They are famous for cutting and collecting leaves, hence the name. As many of you probably know, they do not eat these leaves. Trails of tens of thousands of ants travel into the rain forests and collect leaves all day. A single colony can collect over a tonne of plant material per year.

Atta cephalotes
Atta cephalotes workers bringing leaf fragments hack to the nest along their cleared trails (Alex Wild).

These leaves are brought deep underground into the nests where gardens of fungus are cultivated. The fungus is what they eat. They discovered agriculture millions of years before humans! Each leaf cutter ant species has a specific species or strain of fungus associated with it. Their evolutionary history is so long and intertwined that the fungus is only found in the nests of leaf cutter ants and nowhere else. So how do they get their fungus? Well before the virgin queens leave their mother nests they collect a small pellet of the fungus. This will be used to found their own gardens of fungus! Pretty cool if you ask me. The fungus in modern nests is likely the same line of fungus used millions of years ago!

Acromyrmex versicolor
An Acromyrmex versicolor Queen with her first eggs and the tiny fungus pellet that will sustain her and millions of her children (Alex Wild).

With 8 million ants and huge fungus gardens, these nests get very hot and filled with toxic Carbon dioxide. So how do they survive? Air conditioning. Not joking. Air conditioning. If you look at the surface of a leaf cutter nest you may notice chimney looking structures.

The chaco leafcutter ant Atta vollenweideri forms the largest colonies of any social animal on earth.  Mature nests such as the mound pictured here may contain several million ants.

Resistencia, Chaco, Argentina
Chimneys on the surface of an Atta sp. nest (Alex Wild).

These chimneys use the breeze to draw fresh, cool air into the nest by pulling out the stale air. An ingenious passive system vital for the colony’s survival. The crops cannot over heat or they will die and the colony will be doomed to starve. A grim fate really. These fortresses are some of the only things that can resist swarms of army ants. With their ferocious soldiers, they make a mean foe for anyone. They can cut through flesh like it is nothing. I have been bitten by one of the smaller workers and I can tell you I will not be messing with a soldier. Ever.

Atta laevigata
An Atta laevigata soldier showing why you don’t mess with them. Their shiny heads are full of muscle specifically designed to make you regret picking on them (Alex Wild).

So there you have it. These animals with brains the size of grains of sand have developed some of the most complex societies on earth. They developed farming and air conditioning millions of years before humans even existed. Not bad if you ask me. This remarkable feat is due to something called Swarm Intelligence, look forward to another post dedicated to that!

Acromyrmex echinatior
Acromyrmex echinatior workers and their fungus gardens (Alex Wild).

I haven’t covered everything that makes Leaf cutter ants amazing. If you are interested in learning more, please comment below or join our Facebook page and let me know there. If you like what I am trying to do here and you have some spare pennies each month, please consider becoming a Patron here. You will get loads of perks depending on how much you pledge. And you will have my undying appreciation. I hope you have enjoyed and thank you for reading,

Alex.

References

Hölldobler, B. and Wilson, E.O., 1990. The ants. Harvard University Press.

Hölldobler, B. and Wilson, E.O., 2010. The leafcutter ants: civilization by instinct. WW Norton & Company.

Mueller, U.G., Scott, J.J., Ishak, H.D., Cooper, M. and Rodrigues, A., 2010. Monoculture of leafcutter ant gardens. PLoS One5(9), p.e12668.

Quinlan, R.J. and Cherrett, J.M., 1979. The role of fungus in the diet of the leaf‐cutting ant Atta cephalotes (L.). Ecological Entomology4(2), pp.151-160.

Weber, N.A., 1972. Gardening ants, the attines Memoirs of the American Philosophical Society. Philadelphia, PA.

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