The cheesy truth about OHA


June 11, 2015

Photo courtesy of, and copyrighted by, Gene White,

Photo courtesy of, and copyrighted by, Gene White,

Tapinoma sessile — or odorous house ant/OHA to his friends (and enemies) — is known for its unmistakable scent. If you’ve dealt with this particular pest, you surely know the smell and would probably describe it as smelling like … what? It’s news to me, but evidently the go-to olfactory analog for pest management pros and entomologists alike is rotten coconut.

I’m no fan of coconuts, but I know what they smell like. Rotten coconuts, on the other hand, require me to use my imagination. Even then, I still doubt I could name that scent in a blind smell test. Maybe they smell like a pina colada from Applebee’s. Or an Almond Joy candy bar left out in the sun?

Thanks to Dr. Clint Penick, a biology researcher at North Carolina State University, and a feature about him on, I needn’t lose any more sleep struggling with the mystery of the rotten coconut scent, and, by extension, OHA. They smell like (drum roll, please) … blue cheese! And it’s been scientifically proven! Being a super-fan of the unconventional burger topping, that’s a smell I know by heart. Like most cheese, blue cheese tastes better than it smells.

The smell of blue cheese and the OHA are caused by the same class of chemicals, known as methyl ketones. Who knew? The same study revealed there is no chemical relationship between the ant and coconut.

But wait! There’s more! When Penick (fun fact: he founded the punk band Army Ants in middle school, played guitar in the band Kids Like Us and still keeps up with the scene) buried a coconut for a week and then excavated it for a sniff, it was covered in blue mold that smelled like blue cheese. The mold produces the same methyl ketones. Ta-dah!

While it’s not exactly the scientific discovery of the year, no tax dollars were spent on this elective experiment, so who can complain?

In fact, there is an important takeaway lesson here I think most of us immediately recognize: If you don’t have blue cheese within reach to top your burger, rotten coconut or OHA will do in a pinch …

No, wait. Let me try that again: The takeaway is, PMPs now have a way to help describe the smell of the stinky pest when communicating with customers.



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  1. Richard says:

    Will you hit the nail on the head with that discription