Every other Friday on Morning Edition NHPR’s Sam Evans-Brown tracks down answers to questions about the environment and outdoors for our listeners in a segment we call “Ask Sam.”
Barb in Goffstown asks: “I’m calling about black ants which I refer to as rain ants. I had an explosion of them yesterday in my various areas of the house. And so late at night I killed about ten of them, and felt like I’ll deal with them in the morning, and when I get up in the morning, they weren’t there. There was one live ant, dragging a carcass. I know they don’t want dead ants in their nest, but why do they bother with dead ants that are elsewhere?
An honest-to-goodness murder mystery! Do you think we could turn this into a hit true-crime podcast series?
For starters, ants clean out their dead from their nests in order to make sure the whole colony doesn’t get sick. It’s a behavior triggered (as almost all ant behaviors are) by a chemical “smell” that tells the other ants “oh, that’s garbage.”
But there are many unanswered questions in this mystery.
I reached out to Alex Wild—who runs the University of Texas at Austin Insect Collection, and is an amazing insect photographer—to answer this question, and right away it became clear that we needed more information. He equipped me with some questions to ask Barb, and I called her back.
Did the ants have wings?
To start, it’s not clear what kind of ant we are actually talking about. Rain ant is the popular name of a whole bunch of different types of ants. They’re called rain ants because they do their mating flights right after it rains.
“The rain helps them synchronize their mating flights across colonies because it doesn’t do any good if only one of the colonies sends its winged ants up and none of the other ones do,” says Wild, “Then they just get inbred, and no one wants inbred ants.”
This coordination is stronger in some places than others. In the UK, so many ants take to the wing that “Flying Ant Day” is a summer rite of passage.
If these ants had wings, it might be a sign that there was a nest somewhere in her house, and the ants might have embarked on an ill-fated mating flight that never got out of the house. That would help us at least narrow down the species of ant.
However, Barb burst our bubble. “No they did not have wings,” she confirmed.
There goes that theory.
Were all of these ants the same species?
If the ants that were carrying the dead bodies a different species, it’s possible that a rival colony had decided that those ants Barb squashed are actually free calories.
“It turns out ants eat each other all the time,” says Wild, “Just other species. They don’t usually eat members of their own species because you get diseases through cannibalism.”
While she can’t be sure, Barb says “my hunch is that no, this was the same species.”
[Sad Trombone Sound Effect] There goes that idea.
Did they smell like blue cheese when smooshed?
A lot of ant species are itinerant and move their nests at the drop of a hat, and in fact an event like a big rainstorm can make them decide to move. “There are a lot of ants that just don’t invest very heavily in building a nice, deep permanent nest,” says Wild.
This is particularly the case with the infamous Argentine ant that is in the process of taking over the West Coast. Whenever there’s an extended period of wet weather in California, huge super colonies pick up and move indoors.
“I used to live in California and remember having an entire colony of Argentine ants with hundreds of queens and tens of thousands of workers in a big mill on my ceiling,” Wild recalls.
So perhaps Barb was briefly playing host to a bunch of ants who had decided that in fact her house was their nest. “If they’re inside the house, it might well be that the ants are still thinking of it as inside their colony because they’re not getting the big air currents or bright lights they get from outside,” he says.
This is my current front-runner when it comes to explanations for why these ants were carrying their fallen brethren away, but as is so often the case with insects the answer could just as well be, “we don’t really know.”
However, a fun side now a common Northeastern ant that may have been the culprit is called the odorous house ant, because when you smoosh them they smell like blue cheese or rotting coconuts. And apparently, smooshing and sniffing ants is a common way of identifying them: citronella ants are so named because they smell like lemon verbena when smooshed.
In other words, don’t just swat those ants with a shoe, sniff them afterwards too!
Sam Evans-Brown, is host of NHPR’s Outside/In which you can subscribe to where-ever you get your podcasts. If you’d like to submit a question you can record it as a voice memo on your smartphone and send it to email@example.com, OR call the hotline, 1-844-GO-OTTER, OR submit it here.