A common response to seeing an ant inside your house is to stomp on it. But if you crush a member of the ant species Tapinoma sessile, you might catch a whiff of a strange smell—a smell that reminds some people of blue cheese, rancid butter or rotten coconut. In fact, the smell is so noticeable that the insect’s common name is the “odorous house ant.” And many people call it the coconut ant.

In an effort to figure out why people have these reactions, researchers enlisted visitors at an event called the North Carolina BugFest. One-hundred-forty-three volunteers smelled smushed ants and were asked to identify the scent from four choices: blue cheese, rancid butter, rotten coconut or just other.

Although Web sites overwhelmingly call the smell rotten coconut, almost 40 percent of the human judges picked blue cheese and about 25 percent picked rotten coconut. More than 30 percent went with the choice of other.

The scientists then analyzed the chemicals responsible for the ant odor, as well as the smelly chemicals in blue cheese, fresh coconut and coconut buried underground for three days. It turns out that the chemistry of the ants’ scent is indeed similar to that of blue cheese and rotten coconut. But not to fresh coconut. And the researchers note that the Penicillium microbes that turn coconut oil rancid are also involved in the production of blue cheese. The study is in the journal American Entomologist. [Clint A. Penick and Adrian A. Smith, The True Odor of the Odorous House Ant]

The researchers also noted that the most common write-in candidate as a description for the ants’ aroma was “cleaning spray.” And one little girl told them that the ants “smelled exactly like her doctor.”

—Cynthia Graber

[The above text is a transcript of this podcast.]