Here is a condensed version of our presentation on leafcutter ants Atta Cephalotes.
“It is the little things that rule the world” - E.O. Wilson
I would just like to say, even though our results are opposite from what we were expecting, the fact that they are opened up hundreds of other questions and definitely made me think a lot more and more highly of these hardworking females. Ants!
The leafcutters are one of the most specialized of all the ants. They are the underground farmers who cultivate a fungus, Lepiotaceae, by harvesting fresh vegetation for the fungus to grow on which they bring back to their underground nest chamber. Less complex leafcutters let their fungus grow on dead insects and not strictly on fresh vegetation, they also do not have as many castes. The leafcutters we looked at were more complex, have the largest nests (size of school buses sometimes) that have hundreds of fungal gardens and dump chambers (for spent and contaminated fragments). It is a obligate symbiotic relationship, the ants and the fungus completely dependent on each other for survival. The larvae feed exclusively on the fungus and depending on the species the adults feed mostly on sap and supplement their diet with the fruiting fungi.
They are colonial, and eusocial, there are physiological differences (one reproductive caste, the queen, and a nonreproductive caste, the workers). Among the worker caste there are many other subcastes differentiated by morphological differences that dictate task partitioning. The largest class (maxima) are the soldiers who guard the nest and clear the trails, the media are the workers who cut and bring back leaf fragments to the nest, and the minima, the smallest class may be the most important, they tend the brood and the fungal garden and help chemically mark the trails. They are also seen frequently outside of the nest “hitchhiking” on leaf fragments getting carried back to the nest by media workers.
There are several theories as to why they hitchhike: parasitoid defense (phorid fly) for media workers, sap-feeding, conserving energy, marooned to the leaf, and leaf preparation (cleaning leaf of potential contaminants before entry to nest). We tested the last hypothesis but found that minima were spending more time on clean leaf fragments than on dirty, fungal-treated fragments. If interested as to why we think so… just ask me in person and I’ll go on and on.