An ant’s mandibles are the perfect tool for a variety of important activities, from chewing up food and transporting materials to self defense. While all ants use their mandibles for similar purposes, the exact morphology (size and shape) of these jaw protrusions can vary wildly across the ‘antimal’ kingdom (anticipate more puns).
“What do you call a 100 year old ant?” An antique!
While mandibles are a universal characteristic in most ant species, the term ‘mandible’ is even more universal, describing the jaw-like structure in mammals and fish as well. But our jaws differ quite significantly from the mandibles found on these arthropods. For one, we move our jaw vertically via the temporomandibular joint (TMJ for short) in order to carry out everyday activities like speaking and chewing food (the only activities worth doing!). Ants move their mandibles back and forth in the horizontal direction. One interesting question that arises is, how did ants end up with this type of mandible, whereas humans and other mammals got something different? Did they both originate from a common ancestor 590 million years ago, or are jaws just so crucial that entirely separate species had to develop their own tools?
In thinking about the mandibles of ants, as I quite often do, I had an urge to see these incredible structures with my own eyes. I pulled out my trusty foldscope and ventured out onto campus in search of a new specimen. Once I had identified an ant of interest, I gently placed it on a piece of tape, which I laid on my glass slide. I aligned the specimen with my lens, held it up to the light, and witnessed a breathtaking sight.

It was hard to imagine that I was able to see this tiny creature’s features so vividly with a piece of equipment that I had folded myself! I could clearly make out the structure of the mandibles, which appeared to extend anteriorly before curving inward and thickening. Rather than ending at a single point, these mandibles appeared have a longer, serrated edge that ran parallel to the ant’s body. I became interested in finding out what type of ant I was looking at, so I did a quick google search to determine the most common ant species in the Bay Area. Since mandibles vary so much in morphology, it might actually be possible to identify which ant I have captured using the video of the mandibles and nothing else.

• Argentine Ant
• Carpenter Ant
• Pharaoh Ant
• Thief Ant

The four ants I found to be most common in the Bay Area were the Argentine ant, the Carpenter ant, the Pharaoh ant, and the Thief ant. I immediately ruled out the Pharaoh ant and Thief ant because of their eye morphology. The Thief ant’s eyes are much too small, and the Pharaoh ant’s eyes are too far to the side of its head. In deciding whether my ant was more likely an Argentine ant or a Carpenter ant, I took a closer look at the mandibles of each species. The carpenter ant’s mandibles are thicker and darker than those of the Argentine, with very little forward protrusion before they begin to curve inward to the serrated edge. The ant in my video has thinner mandibles than these, just like the Argentine ant. For this reason, I concluded that the most likely species of my specimen is the Argentine Ant. Originating from South America, these ants have reached almost every continent in the world, and are prolific in California.
Do you think my classification was correct? I’d love to hear your thoughts on what type of ant I am looking at. And if you come across an ant with particularly strange mandibles, please collect a specimen and share. There is something magical about watching these little creatures living and breathing beneath the lens, moving their mandibular structures at will.