Used coffee grounds can be recycled a number of different ways, ranging from using them as a skin exfoliant, a fertilizer or for those artistically inclined, watercoloring and even dyeing easter eggs. Coffee grounds reportedly can also be used to repel ants, which may be comforting for those seeking to guard their kitchens against the invertebrate intruders. Curious as to what exactly it is about coffee that repels ants, I turned to my Evolutionary Biologist & Ecologist friend Benjamin Blanchard, a Ph.D. candidate at the University of Chicago who studies ants.
How do ants sense odorants, chemical compounds, and decide what is pleasing or repulsive? Is there anything about coffee or specifically caffeine that might not be appealing to ants?
Benjamin suspected that the repellant characteristic of coffee might have something to do with the fine-grained nature of the grounds. He shared that, “ants sense chemicals and “taste” objects using their antennae, which often have lots of hairs. Also, they have little spurs on their front legs that they use to clean their antennae – a form of grooming! It is possible that the ants don’t like getting fine coffee grounds stuck on their antennae and in their spurs, and thus avoid coffee.”
Like ants, Benjamin admits that he too is not a huge coffee fan – humorously exclaiming, “If ants are against it, who is for it?!” However, Benjamin does admire the smell of coffee, which he describes as one of his favorite scents in the world. He posited, “if only coffee tasted exactly like it smells, I’d probably join the ranks of those who have a least a cup every day.” Shockingly, he acknowledges that in his entire lifetime he’s probably only had a few cups.
In continuation of a special series of interviews with scientists, it is my pleasure to present Benjamin Blanchard. Here, he describes his research interests, provides a brief introduction to the important role ants play in ecology, and engages with some recent research studies that explore the fascinating relationship between ants and coffee.
Q & A with Benjamin Blanchard
Tell us a little bit about yourself.
I am a PhD Candidate at the University of Chicago advised by Dr. Corrie Moreau, whose lab is located in the Field Museum of Natural History. I grew up in a suburb in southeast Michigan, and did my undergraduate at the University of Michigan in Ann Arbor, double-majoring in Ecology and Evolutionary Biology and Asian Studies with a focus in Chinese. Some of my research takes place in tropical southern China, where I study species competition and predator-prey dynamics in the spiny ant genus Polyrhachis at the Xishuangbanna Tropical Botanical Garden. I am also interested in trait evolution in ants, and I recently published the first chapter of my dissertation on defensive traits in the journal Evolution.
What are your current research interests?
I’m interested in how physical traits (“morphology”) impact the evolution of ants and their ecological interactions with each other and different organisms. In particular, I study this super diverse (and awesome!) ant genus found in tropical Africa, Asia, and the Pacific Islands: Polyrhachis, the “spiny ants”. These ants have a wide diversity of spines – ranging from no spines at all to crazy long spines that curve like fish hooks (and can get caught in your skin a little like fish hooks, too). So, I’d like to know the ecological causes of the evolution of these spines (how did these spines arise?), and the impact that this spine evolution has had on the diversification of this group over evolutionary time (how do spines influence the origination rate of new species?).
(The above image of ant spines was acquired from Antweb.org)
How did you get interested in ants? Was there a single moment you can pinpoint?
Perhaps surprisingly, I didn’t get into ants until some time very late in high school. During senior year, I think. My interest in insects began one fateful day when my family was at my grandmother’s house in western Michigan. My father found this crazy caterpillar on the car, and it had these crazy black and white protrusions (I later found out it was a banded tussock moth). I took the caterpillar and placed it on a leaf, and I was surprised when I could actually hear it chewing! I then found another one, and one of them ended up making it all the way to becoming a moth (the other one died in its cocoon, such is life). This sparked my interest in insects, which led my parents to buy some insect books for me – as far as I can remember, my love of ants began when I read a description of the remarkable ant-aphid relationship. So, by the time I got to the University of Michigan and the Undergraduate Research Opportunity Program, I was searching for an ant project… thankfully, I found one!
Ants are often admired and praised for their work-ethic in works of literature and poetry. If you had to pick an analogy to best characterize or capture the ant work-ethic what would it be and why? Is there a profession you might use to best describe the type of work they do?
Analogy and Profession: Humans.
“Social creatures are such as have some one common object in view; and this property is not common to all creatures that are gregarious. Such social creatures are man, the bee, the wasp, the ant, and the crane.” — Aristotle, The History of Animals (350 BCE)
“We are closer to the ants than to the butterflies. Very few people can endure much leisure.” — Gerald Brenan, Thoughts in a Dry Season, 1978
Introduction to Ants
What type of habitats/environments can ants be found in? Are there any habitats in which they cannot be found or have yet to be found?
Ants are found in nearly every terrestrial (non-water) environment on earth. Exceptions to this rule pretty much only include the extremes – that is, very high elevations (say, the top of Mt. Everest), or very cold regions (say, Antarctica). There is even an ant, Polyrhachis sokolova, which lives in mangrove mud flats and can swim!
What ecological role(s) do ants play in ecosystem/life cycle? Could you give a few examples?
Ants also play a remarkably wide range of roles in several ecosystems. It’s said that leaf-cutter ants in the Amazon recycle about one-sixth of the leaf matter, although this is a back of the envelope calculation. But ants certainly act as “ecosystem engineers”, for example by adjusting soil properties due to their colonies in the ground and engaging in seed dispersal (a process called “myrmecochory”). It is also quite common for ants to have a mutualistic relationship with various plants (“ant-plants”), living inside these plants that provide them special food bodies, while the ants defend the plants from attackers as big as elephants (as shown by work from Dr. Todd Palmer). This sort of behavior, of course, can significantly influence plant and animal distributions. And then you have the remarkable army ants in the Neotropics, which are nomadic and march along in huge trails of 100,000’s of workers, acting almost like a vacuum cleaner that sucks up whatever food it can find. Needless to say, there is a reason people worldwide know about ants – they are everywhere, and play a big role in many ecosystems!
Ants and Coffee
An article published at the end of last year by a group of scientists in Fiji found that a certain species of ant, Phildris nagasau, plants, cultivates and protects coffee plants. When the plant is ripe enough, however, the ant makes its abode inside. The article likened the ant to a “farmer with a green thumb.” What particular attributes from your knowledge about ants might make an ant a great farmer?
Just like human agrarian societies, a necessary attribute for farming is locational stability. Most ant species are grounded by the location of their colony, and this allows for such things like the evolution of farming. Furthermore, many ants are excellent at exploiting various resources opportunistically – if the food is there, worker ants will use it.
For example, several species exhibit what is called “facultative mutualism”, which means that the species will have a mutualistic relationship with another species (say a tree, or an aphid) if it’s available, but doesn’t necessarily need that relationship to survive. It is easy to see how this sort of facultative behavior could be an intermediate step between no mutualistic relationships and the more complex mutualism you described with Philidris nagasau. Lastly, like human societies, division of labor is key – because some ants tend brood and some (the queen or queens) produce offspring, ant societies are able to devote some workers to farming.
While an ant species that plants, cultivates and protects coffee plants ultimately with the goal of inhabiting the coffee plant is not advantageous for coffee growers, and coffee farmers may not be harnessing at least this species of ant for coffee production anytime soon, there is perhaps something to be admired about Phildris here. As Botanist Susanne Renner remarked: “this one ant has bred six different types of coffee plant.” The article noted that ants are a social insect who work in teams, and this may explain their feat as an accomplishment of teamwork. Can you share some thoughts from your knowledge of how ants work together to accomplish a desired goal/outcome that is advantageous for the colony?
Division of labor is a hallmark of ants (as well as other social insects). This allows for task flexibility and diversity within a single colony, which means overcoming obstacles and achieving goals that would not be possible for solitary organisms. However, this task division requires something else: communication.
As is now fairly well known, foraging ants communicate chemical trails. These ants lay trails of pheromones that are then detected by other workers (using their antennae). If the food source is a good one, the trail is continually reinforced until there is quite a significant foraging effort underway. And, an ant knows if another ant is friend or foe using what are called “cuticular hydrocarbons”, which is basically a fancy word for highly accurate, identifying chemicals on the exoskeleton of insects. So, this system ensures that a colony can make accurate choices – and choices that benefit their colony, not an enemy’s!
Another study by Milligan et al. 2016 investigating the effectiveness of insect pest control by ants and birds on coffee farms in Kenya found that ants and birds best regulate coffee plant pests under specific environmental conditions (shade tree canopy). Out of curiosity, what do ants eat? What does the ant diet consist of – is it mostly plant based or are there examples of carnivorous ants or ants that eat other insects? What about a shade tree canopy might make it an ideal environment for work of the ant?
Interesting study! And good questions – ants are highly diverse, and therefore, you can find an insect species that eats almost anything, from scavengers to seed-millers to nomadic fungus harvesters. As for the shade tree canopy, living in a tree may make it easier for ants to avoid predators, and I imagine conditions in and around such trees tend to be a littler moister and darker than microhabitats in areas without trees.
As a biologist who understands and respects the ecological significance of ants, but views them as pests – I find the idea of a pest controlling pests, both interesting and ironic. Any comments here?
Well first, and most importantly, even though it’s true that five of the top 100 most invasive species are ants, ants are a group that consists of over 13,000 species. Why would you judge a whole group based on the actions of a few???
And yes, as your question suggests, ecology is complicated, and sometimes relationships between species yield outcomes you might not expect.
Outside of science, what hobbies do you enjoy?
What other hobbies are there? Haha just kidding…I like riding a bike, reading books, watching TV shows, completing crossword puzzles, talking (lots and lots of talking), playing instruments, playing board and card games, nothing too exciting! And the extent to which I do some of these has fluctuated over the years.
How can people learn more about you and your work?