by Joseph DeSisto
I love scorpions. They’re fast, predatory, venomous … really, everything you could want in animal. So in Arizona, while I was supposed to be collecting caterpillars, I occasionally took a “scorpion break,” flipping rocks and digging in the sand.
We spent a day collecting along Montezuma Pass, a mountain road that winds through Coronado National Forest. Towards the base of the mountain, where pine forest gives way to grassy scrub, I struck gold. Scorpions were everywhere.
By far the most common was the striped devil scorpion (Vaejovis spinigerus), which is found in dry, lowland habitats through much of Arizona and New Mexico. These are big scorpions, approaching 3 inches in length, with a sting that is painful but not medically threatening (except in the case of an extreme allergic reaction).
The biggest scorpions were the mothers, carrying babies on their backs. Although striped devil scorpions can reproduce by mating, if the pickings are slim, a female can also produce young asexually, without mating.
So I wandered through the sun-baked grass, flipping rocks and scrutinizing the ground. I was so focused on my scorpions that I stumbled into one of the strangest things I had ever seen. In the middle of the field was a circular clearing, about six feet across, where no plants grew. There was only sand and, on closer inspection, ants.
The ants in question were harvester ants (genus Pogonomyrmex). Harvester ants are scavengers that subsist mostly on seeds. I watched as teams of ants brought back seeds and the occasional dead insect from the surrounding grassland, stuffing them into small entrances that led to a vast network of underground tunnels and storage chambers.
I’d heard that harvester ants were defensive and had powerful stings, but these ones seemed comfortable with me strolling across their sand garden, and even kneeling to get a closer look. To see if their reputation was justified, I grabbed one and pressed its abdomen against the soft skin of my wrist.
Sure enough, it stung me and administered a healthy dose of venom. The result was a sharp pain, like being stuck with a pin, and this pain grew over the next 30 minutes or so. Ultimately, however, I was disappointed — it didn’t hurt that much. Were these ants, which seemed to have such a well protected territory, aggressive at all?
Perhaps the ants simply weren’t frightened by me. I decided to give them a real threat, and see how they reacted. So I flipped a few rocks, grabbed the first scorpion I could find, and dropped it into the center of the sand garden.
The response was immediate and severe. The moment the scorpion hit the ground, a party of three ants grabbed onto it with their large jaws and began to sting. As they did so, they released a pheromone, a chemical alarm signal that brought dozens more ants to their aid. Within seconds, the scorpi0n was surrounded.
A few minutes passed, and the ants piled on. The scorpion quickly expired, as sting after sting injected deadly venom. Still, the ants held guard over the invader for several hours, as if to make sure it didn’t come back to life.
Harvester ants clearly don’t like scorpions, which makes sense. It’s likely that, if caught alone, a single ant would be easy prey for a 3-inch-long scorpion. But a scorpion, no matter how large, would be unwise to enter a harvester ant colony’s sand garden. Given how quickly and violently the ants responded, I thought that perhaps I too should give them a wide berth. Striped devil scorpions might be large, intimidating, and ready to sting, but they are by far not the fiercest or most venomous animals of Montezuma Pass.