Imagine you only had one night a year to find a mate, because the rest of the time you were deep underground, and mates are only found in the air. You want to avoid mating with your brothers, so you need to synchronize with all the others in the area. Also, you are an ant, and lack Facebook, Twitter, or email of any kind. You don’t even have LikeALittle. What solution has evolved? For the fungus-growing, leaf-cutting ants in Texas, Atta texana, it is quite a remarkable solution, one that solves many problems at once. I’m going to keep using their scientific name because it is shorter and more specific than the common name, and there is a poetry to it. Atta texana, feel the mystery.
To appreciate this ingenious solution to a problem that, let’s face it, wasn’t keeping you up at night, and wasn’t even keeping me up at night, you need a little background in ants. First of all, all ants are social and live in groups that are usually made up of sisters. Typically colonies have a single queen who produces all the eggs. The workers are all female. Males are important for mating and little else in this female society. (Ant researchers seldom get labeled as having male-centric views of their organism.) The males don’t last long after they mate, and generally mate away from the nest with strangers. Typically, a colony is begun by a single mated queen who digs a burrow and raises the first workers by feeding them eggs. The eggs are made by breaking down the flight muscle of the queen. She doesn’t need it any more, since she will never fly again. Some species avoid this lonely period by starting a colony with a queen and a few workers from home, but not this fungus-growing ant. One thing about ants is there are so many kinds that all these generalities are broken in one species or another, except the one about the workers being female. But this is a blog about one field trip on one ant species, not a book, so the generalities suffice.
So, our Atta texana queens need to find a male from another nest, mate with him, and then dig into the soil and begin a new nest, all before a bird spots them. Actually, they need to find several males, for these queens mate multiply, all on a single night, then store the sperm for years. The males get just one shot, expending all their sperm and their lives, on a single aerial mating.
A full, or at least gibbous moon lights the flights. Such a moon stimulates a flight only after a deep rain. The rain softens the soil so the queens can dig into the ground quickly, away from hungry beaks and jaws, and begin their family. It happens in May, and the combination of a full moon, a good rain, and the best month of the year is attended to by all the colonies in an area, so the amorous can find one another. We researchers can also find them if we pay attention to the rain, the moon, the month, and are willing to drop everything, for there is only one chance a year. Actually, this shouldn’t be a problem because the flight is in the early, early morning when we seldom schedule much.
This year, the magic date for mating ants was Friday the thirteenth of May. The moon was 4 days from full. The rainfall was slight, but more than we’d had in months. The month was right, so we joined Rice University professor Scott Solomon at 5:30 AM on a little patch of roadside near Conroe to witness the flight. It is hard to look on the ground for something that happens in the air, but Atta texana mounds about to fly are covered in ants, workers, and the inch-long queens and males. The mounds we watched were not boiling with ants the way I remembered from grad school visits, but they were there, climbing up our boots, everywhere. And we were there, along with a couple of interested undergraduates, Tatiana Fovanova and Ben Ong.
There are lots of fascinating things to study about fungus growing ants as a group, and many people do it, including former Rice University undergraduate, Nicole Gerardo, Koos Boomsma, who hosted us in Denmark, and Ulrich Mueller in Austin. But everyone asks something specific, something that can be answered, at least partly. What Scott Solomon was after on this trip was a relationship I never heard of, that between Atta texana and a cockroach. This tiny cockroach lives in ant colonies, and gets to new ones by riding on queens. Scott needed to catch these queens to study this relationship and kindly invited us along.
The school busses and cars that zoomed past us that early May morning contained hundreds of people who will never know that this was the day, this was the flight, the big morning when queens and males could find each other and mate. I bet a lot of them don’t even realize the sandy soil north of Houston is perfect for Atta texana, the lone member of a mostly neotropical group. Hang out with field biologists, and you can learn about the mysteries that are right under our feet. You missed the flight this year. Maybe you can catch it next May. By then we’ll be in St. Louis where there are no Atta texana colonies. Don’t worry, like Homesick Texan, I’ll still be writing about Texas.
Scott Solomon knew where the ants were.
There is a cockroach visible on the thorax of this ant. It is that bump near the short, left leg.
Queens and males getting ready to fly.
Harvested leaves and flowers.
Scott Solomon, teacher, writer, researcher.
Scott with colleague Tom Miller.
Tatiana and Ben.
That dawn roadside near Conroe.