Interesting Animals: Fungus Growing Ants

A leaf-cutter ant

Leaf cutters have large colonies

Most of you probably are familiar with the leaf-cutter ants, but you may not know that they are fungus gardeners. That's right. These little insects take those leaves back to their colonies where they carefully cultivate fungus using the leaves as fertilizer. The fungus is what the ants eat rather than the leaves. Also, "leaf cutter ant" is a very general term and actually encompass two different genera: Acromyrmex and Atta which contain numerous species. They have a very complex colony set up which even includes a dump where bad leaves and dead ants are taken.

The leaf-cutters are not the only fungus gardeners, however. There are thirteen genera total, which grow their fungus on everything from fresh leaves to flowers, beetle wings to herbivorous insect feces (known as frass). Colony size varies greatly from the ants of the genus Cyphomyrmex that only have around fifty to one hundred ants to the massive leaf cutter colonies. Fungus type varies as well. It is usually in a filamentous form, but the Cyphomyrmex genus uses a globular "yeast" form (which isn't a true yeast).

C. rimosus ant under magnification

I was lucky enough to have the chance to work with the little-known Cyphomyrmex ants, specifically C. rimosus which has been introduced locally. They are very odd-looking with large heads and dark bodies that look like they've been dusted with ash. I went on several hunts to find colonies, turning over numerous logs and excavating them. Then, there were months getting the ants settled into artificial colony setups. It was a fascinating process. There has been very little research done on these ants and they are so little known that they don't even have a common name. They are one of the fungus gardeners that use frass as fertilizer.

Here are all of the fungus gardening ant genera: Acromyrmex, Apterostigma, Atta, Cyphomyrmex, Mycetagroicus, Mycetarotes, Mycetophylax, Mycetosoritis, Mycocepurus, Myrmicocrypta, Pseudoatta, Sericomyrmex, Trachymyrmex

First two images are from Wikimedia Commons under creative commons licenses: one, two. The last one is mine.