For much of the year, the desert can seem like a pretty empty place. If you go out in the early Summer, before the monsoons arrive, it’s dry, dusty, and hot.
After the monsoons arrive, though, the feeling is very different. The sensation is more like being in the middle of a frenetic nature documentary. There’s life everywhere, and you see fascinating things go scrolling by, almost faster than you can appreciate what you’re seeing.
Back in July of 2004, the monsoons came, and I was in heaven. I’d gone anting in the Sonoran Desert around Tucson after we’d had heavy rains the previous day. I could not wait to see what sort of wonders were out.
There were birds singing and calling everywhere, insects flying. The air was cool and fresh, and the colors were vibrant and alive.
And the ant mating flights had begun. The rains act as triggers for the breeding of lots of ant species, and these ants send masses of their winged males and virgin queens out into the world. The males and queens mate, and the queens try to dig new nests just as fast as they can. This is a vulnerable time for them.
The mating flights trigger a near feeding frenzy – the nearly defenseless, protein- and fat-rich queens roaming around the desert floor bring out lots of predators. It brings out other ants, even ants that aren’t breeding.
You’ll see ants that you haven’t seen since last year, all taking advantage of the water and the mating flights.
One morning I was out after an early monsoon rain and came across a beautiful Pheidole spadonia major. Actually, I didn’t know it was Pheidole spadonia until I got home, when I was able to look at my photos closely. That’s one of the drawbacks of anting, sometimes you don’t realize what you’re seeing at the time. I just knew that it was a spectacular-looking Pheidole of some kind with a hugely developed head capsule, a bit like Pheidole militicida.
Although I had visited this wash frequently over the previous year, this was the first time I had seen an ant like this. So a few days later when we had another rain, I went back to the same area to look for more.
And there were a lot of them out on this particular morning. I probably came across three or four nests within an hour or two. The ants were down in the bottom of a shallow wash, in very fine sand/clay soil. The moist soil would stick in clumps to my boots, and laying down in/on it was not very pleasant. I could see strands of what looked like algae on the surface ground, as though this area had flooded sometime in the last week or so. The wet dirt had a fecund, vaguely stagnant smell. There were clumps of small mesquite trees around, most with nearly bare ground beneath.
I first saw the Pheidole by watching for the small workers. They were carrying pieces of vegetation and back to the nest. And a lucky few were taking advantage of the mating flights’ incidental carnage – they were carrying the remains of other insects back to the nest.
I focused on one worker that was precariously balancing a Pheidole xerophila major worker by the major’s extended hind leg. The relatively enormous P. xerophila major looked like a strange blimp floating above the tiny P. spadonia minor worker.
Attached to the dead Pheidole xerophila major worker were the remains of two other Pheidole minor workers. I’m assuming they were also Pheidole xerophila, since there were a couple of warring P. xerophila colonies 20 feet or so away).
The worker slowly worked her way back to her nest, balancing the tangle of ant corpses like a bizarre circus performer. Eventually, she arrived at the nest, and dragged the bodies down below-ground.
The nest entrances were simple, small holes in the ground, with no mound around them. Perhaps there had been a mound previously, but it had washed away in the rains? Stefan Cover, in E.O. Wilson’s Pheidole in the New World book, says of the three colonies he found in Tucson:
…in clayey soil; two had cryptic entrances, and one had a rudimentary crescentic crater of excavated soil. Wheeler’s type series were taken from nests in open sandy soil, the entrances of which were also marked by incomplete craters.
…which would certainly be consistent with the nests I found.
As I watched the nest, a huge, block-like head loomed out of the darkness and blocked the entrance.
Oh, this was cool. It was a major worker. She’d stay like that for minutes at a time, with just her mandibles and antennae above ground.
The big major worker would move out of the way to let minor workers in and out of the nest hole. She sometimes seemed to get in the way as the minors would bring items into the nest.
At one point, a minor worker came struggling back to the nest entrance. She was dragging something enormous. It was the severed head of Odontomachus clarus, a Trap-jawed Ant. The minor worker could…just…barely…move the head.
When the minor worker got near the nest entrance, the major worker stretched out of the nest and grabbed part of the enormous Odontomachus head. I don’t know how the major knew that the minor needed help. Perhaps she saw the minor, or the minor signaled to the major somehow?
In any case, the major braced herself with her rearmost pair of legs still inside the nest entrance, and dragged the Odontomachus into the nest.
A minute or two after pulling in the Odontomachus head, a major came out of the nest and roamed around for a bit.
I wonder if this wasn’t the major that had just pulled in the Odontomachus head. Maybe this was an effect similar to leaving cookie bait out for Pheidole militicida – that the eagerness for more of the bait brings the normally shy major workers out of the nest?
Perhaps that explains the Pheidole spadonia major that I’d found a couple of days previously, it had been lured out of the nest by the promise of insect fragments?
In his marevelous book on Pheidole, E.O. Wilson (2003) describes Pheidole spadonia as a seed-eater Certainly, these ants were bringing in seeds and vegetable matter into the nest. I’d imagine that situations like this, were there is insect protein out there just for the taking, must seem like a holiday for the ants.
Sources:
Wilson, Edward O. (2003). Pheidole in the New World: A Dominant, Hyperdiverse Ant Genus.
