This past weekend at the North Carolina Museum of Natural Sciences annual BugFest, we convinced a couple hundred people to sniff ants. We started off light, with a bouquet of lemon and citrus from the citronella ant, Lasius claviger. Then we plowed ahead, shoving an angry carpenter ant under the nose of anyone who would take it to demonstrate the acrid, vinegar smell of formic acid. If the participant was still with us, we moved onto our main quarry: the odorous house ant.
First, I have to admit that through this entire exercise I had an ulterior motive. The odorous house ant is unquestionably odorous, but there is debate about what exactly that odor is. OK, maybe “the debate” is more of a personal grudge, and maybe I spend a little too much of my free time smelling ants, but please bear with me on this.
The odorous house ant is one of the most common ants in North America. It belongs to a group of ants famous for smelling like blue cheese. Again, “famous” might not be the right word here, but most species in this group do smell amazingly similar to blue cheese. This is where the controversy begins. Online, numerous websites purport that the odorous house ant is the exception to the rule. Instead of blue cheese, these sites claim that the odor is…rotten coconut!
Now, I don’t have a problem with ants smelling like coconut. In fact, I really wanted the odorous house ant to smell like coconut. After moving to Raleigh from the west coast, where the odorous house ant is rare, I was looking forward to my chance to smell the “coconut ant.” So when spring finally came and a colony of odorous house ants emerged in my yard, I grabbed a couple workers and held them to my nose. What happened? Nothing. I mean they smelled, but they smelled like any other blue cheese ant. There was no coconut, rotten or otherwise, and certainly no, “Sickening-sweet smell, like a coconut piña colada,” that I read on one website.
Not unlike rotten coconut itself, the experience left a bitter taste in my mouth. So I turned to the internet and found that over 80% of the sites mentioning the odorous house ant also described some “coconut-like” smell (Fig. 1A). Only two sites out of a hundred mentioned blue cheese! Could my nose be that wrong? I doubted it, so I went to the people. This is how the unsuspecting participants of BugFest got roped into my crusade to identify the smell of the odorous house ant.
At our display table, we gave the participants four choices: A) rotten coconut, B) blue cheese, C) rancid butter, or D) other, which allowed a write-in candidate. I did my best to remain non-biased, but in the end I was vindicated when blue cheese won by a slim margin (Fig. 1B). Rotten coconut got a fair number of votes also, but “other” came in second place. Topping the list for write-in candidates: “cleaning spray” and “paint,” and one little girl said the ants smelled exactly like her doctor.
So what is the real answer? We don’t know yet, but we’re not stopping there. In collaboration with Adrian Smith at the University of Illinois, who is working on the trail pheromone of odorous house ants, we’re conducting a chemical analysis. We’ll sample the compounds released by blue cheese, rancid butter, rotten coconut, and of course the ants. Maybe we’ll even try to find that little girl’s doctor! Who knows? When the results are in, we’ll write up our assessment and share the results with the world. Until then, we’ll be trying to figure out how, exactly, to rot a coconut. Any ideas?
Cool. I’m just not sure what rotten coconut smells like, so trying to pin it on an ant w/b difficult. I’m sure you will find out!
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Actually, I find that the fragrant ants in our NC remind my wife and I of Circus Peanuts candy.
I myself have dealt with these “famous” ants, and quite recently at that. I have squished quite a few, and after so, I smelled the faint scent of Blue Cheese. Who would have thought such a tiny insect could carry such a bold scent once killed.
They don’t smell like rotten coconut or blue cheese at all, they smell like some type of chemical. Not sure what, maybe a household cleaning spray or something. All I know is that when I crush them, I 100% smell a chemical like odor. Which is what you’re smelling anyway, since these ants are producing alarm, trail-marking, anti-fungal and antibacterial, and communication chemicals of their own.
It makes more sense to describe the odor as being similar to a man made chemical than something like blue cheese..
I recently got these small tiny ants…when smashed they smell to me like a cleaning product. Man made like you said not rotten or rancid anything, nor blue cheese or coconut. Definately a cleaning product.
To me the odor has a similar pungency to oct-1-en-3-one, the chemical responsible for the metallic taste one gets from touching steel. I believe that the chemical in question is 6-methyl-5-hepten-2-one, which has a somewhat similar structure and has been demonstrated as being present in extracts of the ant.
Thanks Morrie! Methyl-ketones seem to be the source of the smell (and that’s the right compound for the alarm pheromone). We have a paper in press for this study on the odorous house ant scent (coincidentally, it’s written with the lead author from the report attached above). We’ll be posting when it comes out.
Cool Im not crazy. Nail polish is the smell. Paint. My son pointed it out to me. Taste like they smell. Could it be from eating through walls.
I got here by searching. Why do our ants smell like blue cheese?
I got here by searching ‘Ant odour coconut’! Haha
I’m trying to figure out if I have odorous house ants. I think I do. My husband says they smell like turpentine. I’m not good with identifying smells, but it is chemically to me. I hate blue cheese so I stay away enough that I don’t know what it smells like.
If this is the ant that I have been crushing and smelling, the scent reminds me of artificial banana flavoring.
Absolutely! that’s what our family thinks, also! Perhaps it depends on your locality, and what they process in their hills. We live in central Oklahoma. Where do you live? (give me a generality… I really don’t plan to come sniff your ants, Ha!)
I’d have to say it smells like artificial banana flavoring
yes, definitely like a cleaning product or possibly nail polish but I haven’t smelled this for years and have only a faint memory of this. i have killed three, one crawling on my arm and two found in my drinking glass beside my bed.. i recently bought potting soil for growing flowers indoors . could the ants be coming from this soil? i doubt it but felt i must ask.