They're aggressive, swift in the attack, and deliver a potent, neurotoxic venom.
Mountain lions, raptors and rattlesnakes – West Texas doesn't lack for iconic predators. But centipedes may be the fiercest of the region's carnivores. They're the original survivors, members of an ancient lineage.
They possess only the rudiments of eyes, using antennae to seek out prey. They retreat beneath rocks and logs, in woodpiles. In centipedes, we seem to glimpse life's dim origins, the first instincts of pursuit and survival.
Our visceral response is well-founded. Centipedes were among the first creatures to colonize dry land, 430 million years ago. On solid ground, centipedes are the original predators, the first hunters. They're as old as coral reefs, as vascular plants, as sharks.
And they flourish today. Centipedes are found on every continent but Antarctica. In West Texas, two species are common.
Mike Medrano is chief of resource management at Guadalupe Mountains National Park. He's an arthropod expert. West Texas, he said, is home to North America's largest centipede.
“Scolopendra heros is one of the common species around here – it'll get 6, 8 inches long,” Medrano said. “A baby bird or a baby mouse would not faze it at all. Scolopendra heros is that dark-blue, purplish color with yellow-orangish legs. They're pretty distinctive. I've seen some specimens that are almost red.”
In various subspecies, Scolapendra heros – known as the giant desert centipede or the Texas redheaded centipede – is found from Louisiana to Arizona and northern Mexico. West Texas is home to a second, slightly smaller centipede – Scolopendra polymorpha, the tiger or banded desert centipede. Its coloration varies. It's typically brown, red or orange, with a dark stripe on each body segment.
Both West Texas centipedes typically have about 20 body segments – or a total of 40 legs.
Millipedes and centipedes share a common ancestor. Millipedes feed on dead plants and burrow in desert soil. But as hunt-and-seek predators, centipedes are built for speed, Medrano said.
“The spacing of their segments in elongated, which gives them a longer gait,” Medrano said. That “makes them fast, whereas the millipedes are compressed, and that space between the segments is shortened, to give them power for digging.”
When it comes to prey, centipedes aren't choosy. They'll consume insects, spiders and scorpions. And they're one of the few invertebrates that will eat vertebrates. A South American centipede can catch bats in mid-flight. In West Texas, centipedes feed on small mice. They enter nests to take baby birds.
As with many desert predators, centipedes here do their hunting at night. The centipede's venom attacks the nervous system, paralyzing its prey. Centipedes inject their venom with a pair of poison jaws called forcipules.
“It's a modified pair of front legs, so they're kind of opposing when they bite,” Medrano said. “If you're looking for a centipede bite, you're looking for marks from the side, as opposed to a spider that's got fang marks going down.”
Centipedes can find their way into shoes and clothing. For humans, centipede bites are rarely if ever fatal. But they are painful. And they carry a high risk of infection, Medrano said.
“And they're poison jaws are just filthy with bacteria, because they're carnivorous,” he said. “So if you do get bit, it's not so much the venom that hurts, it's the post-bite infection that's the big concern. So people get bit, they go to the hospital, and the first thing they do is dope them up with antibiotics for that reason.”
As the park's resident arthropod expert, Medrano is often called upon to remove centipedes found in the visitors center. He said it's one of the few assignments that can spook him.
“There have been times when I've had to step on them on their back end, and their front end comes up and starts chewing on the front of my boot,” Medrano said. “Centipedes are really the only thing that give me the creeps, just because they're fast and they are venomous. I can deal with spiders, I can deal with scorpions – that doesn't bother me. But the centipedes – I've got a healthy respect for them for sure.”