It is my opinion that in terms of animal societies, none rivals the complexity and creativity of the ant. The social organization and things these guys can do is freaking amazing. Kurt Vonnegut even wrote a short story about the discovery of frozen ants that had complex social structures and ideologies (and revolutions). It’s called The Petrified Ants, check it out. Anyway, my point is, ants are perfect for this blog, and today I’m posting about an especially interesting species of ant, the allomerus ant.
Allomerus ants are a species of tropical ant that lives in the Amazon rainforest. The ant has a mutualistic relationship with Hirtella physophora, a Amazonian tree that is almost never found without its ant companions. The ants live inside leaf pockets in the tree, which are hollow areas between the leaves and stems. Trees normally hold around 1200 workers, spread out so there are only around 40 workers per leaf. This relationship between ant and plant (hey, that rhymes!) is quite complex, and it seems like both parties have evolved to take advantage of the others traits.
The benefits to the ant are pretty straight forward; they get a safe place to live, and the plant secretes nectar in the leaf pockets to help feed the ants. But the plant also gains from the relationship. You see, allomerus ants are extremely aggressive insect predators, and help protect the tree from insects that would otherwise harm the tree. The leaf pockets also contain more stomata, or pores, to absorb the carbon dioxide the ants give off.
The ants don’t end their interspecies relationships there. They also have a friendly relationship with a fungus, in the order Chaetothyriales. Many fungi grow alongside the ants as they live in their little houses in the tree, but only this particular mould is cultivated by the ants. Yes, ants cultivate things. They are crazy cool. The ants use this mould to construct traps in which they catch unwary insects.
The traps are built on the stems of the tree, and are made to look like part of the tree itself. The ants trim away some of the hair-like projections on the plant, and then rearrange them as a structural base. Regurgitated mould acts as glue to hold these in place, and the mould will continue to grow once regurgitated, providing additional support. The ants then hollow out holes in the stem and tuck themselves in, sitting with their jaws open, just waiting for a foolish insect to come wandering by.
Once an animal does land on the branch, a single ant will pop up and grab one of the prey’s legs, secreting pheromones as it does so. While the ant struggles to keep the much bigger prey captive, the pheromones call other ants to arms. Helpers arrive and grab separate legs, stretching the victim like a torture victim on a rack. Once the prey is secure, the ants sting the insect until it dies, then bring it back home to divide the spoils. Using this technique, ants are able to capture prey that is much, much bigger than if they were hunting alone. One study tested the ability of allomerus ants to capture and hold a grasshopper down, an insect that is 142 times the size of a worker ant. This is the equivalent of a 175 pound person holding down a struggling 25,000 pound object. Of the twenty grasshoppers tested, only seven got away completely. Not too shabby for our little ant friends. So to all my readers who are grasshoppers or other insects, stay away from allomerus ants!
The complexity that allomerus ants show in there interactions with each other and other species is quite remarkable. One can only imagine we will find more amazing things about these little creatures the more we study them. Maybe one day we’ll even find violin-playing ants, like in Vonnegut’s story. Who knows?
Cover photo by Photo by Philipp Hönle, used under Creative Commons Licence.