When you hear the term ant farm, an image probably comes to mind of the plastic, transparent container of soil through which a colony of ants can create tunnels and nests while safely confined in your home. Admittedly, I have never kept one of these, but I have always been curious about them.
Regardless, that is not the kind of ant farm that I am referring to in this post. I am not as interested in people "farming" ants as I am in ants doing the "farming." Which they absolutely do!
My interest in this subject began in 2014 when I noticed something strange was happening to the leaves of my peach tree. See, I have a beloved peach tree that I tend to anthropomorphize. After raising her from a root-induced twig, I christened her Melba, and she has been a reliable producer of delicious peaches for years. So when the tree's leaves began to curl and ripple, I noticed right away. Concerned that a disease or fungus was infecting the tree, I inspected the leaves carefully and was astonished at what I saw- inside the leaves were groups of tiny aphids, happily enclosed and shaded from the sun. That's when I saw the ants. Every inch of stem and branch was crawling with little black ants. It took a bit of research to realize that the presence of the two insects was related. Ants, it seems, actively work to curl the leaves to create a shelter for aphids...which they raise and protect...in order to "milk" them...
This has the potential to hurt the tree, but I couldn't bring myself to get rid of them and, thankfully, the peach tree was fine.
What they collect is not "milk" in the dairy sense that we think of it; aphids are not mammals after all. Instead, the aphids secrete a sugary sap that the ants collect in a process that we just call milking. Aphids are very good at injecting their mouthparts into leaves and stems to extract the plant's nutrient-rich fluids. The ants are not, they need richer food to sustain themselves. Sugar, as it happens, is a favorite of ants (you probably know this from your last picnic or having dropped the smallest sugary treat onto the ground).When under the care of the ants, the aphids are protected from predators by the defensive ant caretakers, and as a result the aphids will purposely secrete a concentrated sugar nectar from their abdomen for the ants can lap up.
It is an amazing example of a mutually beneficial symbiotic relationship, more simply called mutualism.
In biology, mutualism is defined as a relationship between two species in which both species benefit. Two of the most common examples are pollinators with flowers and the Disney favorite, clownfish with anemones.
Pollinating insects, like honeybees, hummingbirds, bats, and butterflies, feed primarily on the nectar that is stored within the flowering structure of a plant. These pollinators fly from flower to flower to drink the nectar, but to reach it, they must push past the anther of the flower. The anther is coated with powdery pollen, dusting the pollinator so that when they land in the next flower, some of the pollen might fall in and pollinate the plant. The pollinator is happily fed, and the flowering plants are able to reproduce.
Clownfish actually live inside their host, but it is not the same as another symbiotic relationship, parasitism, because they don't feed directly on their host species. Anemones are known for having stinging cells, called cnidocytes or nematocysts, on their tentacles. They are close relatives of jellyfish and corals, and each member of the cnidaria phylum has these stinging cells. Most fish are harmed by them as the anemone will typically sting fish, bring its cells inward, and eat the stung fish when it enters the center of its disk (basically the mouth). Clownfish are unique in that they are immune to the sting. They produce a mucus layer over their scales that protects them from the nematocysts and allows them to live within the tentacles without enduring any harm. Therefore, the clownfish are protected from other predatory fish that are not immune from the stinging cells. The anemone benefits by being cleaned and even directly fed by its tenant. Clownfish are also fairly aggressive, and they can drive away butterflyfish that nip at the anemone's tentacles.