Camel Spiders Are Fast, Furious and Horrifically Fascinating
Yet another mystery about these arachnids: Why are they so intent on mass-murdering ants?
/https://tf-cmsv2-smithsonianmag-media.s3.amazonaws.com/filer/0d/5a/0d5a571c-597a-45b0-87b3-ce2ec3047ebd/e45c17.jpg)
Imagine waking up to find a hairy-faced, fleet-footed monster on your doorstep—a creature that looks like a mashup of Shelob and Grendel, with jaws nearly one-third the size of its body. Jaws that have just sheared most of your nest-mates in half. This was the stuation for an unfortunate colony of ants that recently fell victim to a camel spider in Israel.
And thanks to the keen eyes of photographer Olga Chagina, we have video.
Watching the camel spider mow down its prey with efficiency and seeming nonchalance is certainly mesmerizing. But what's actually going on here? The truth is, even the experts are unsure. Which means we can add ‘ant massacres’ to the already long list of things we have yet to figure out about these elusive, hand-sized arachnids.
Camel spiders, more properly known as solifugids, are an elusive order of arachnids native to deserts all over the world (pretty much everywhere except in Australia and Antarctica). There are thought to be around 1,100 species, most of which haven't been studied. This is partly because the animals are a notorious pain to observe in the wild, and partly because they seem to wither away in the lab.
While many of their common names refer to other kinds of creepy crawlies—wind scorpions, sun spiders—they actually belong to their very own order of Arachnida, separate from true spiders. Paula Cushing, an evolutionary biologist who studies solifugids at the Denver Museum of Nature and Science, says some research suggests the animals are most closely related to pseudoscorpions, while other work links solifugids to a group of mites.
What’s not up for debate is that solifugids are just plain cool. “They’re voracious predators, and they will tear apart anything they can get their jaws on,” says Cushing.
For solifugids, (almost) everything is on the menu
We know surprisingly little about these critters, but a review of solifugid diets published in 2014 shows that they eat everything from termites, wasps, beetles, and silverfish to scorpions, spiders and other solifugids. One thing they do not seem particularly fond of eating? Ants.
Watch the video closely and you'll never actually see the solifugid eat any of the ants it kills, says Cushing. Of course, it’s possible that the arachnid is merely choosing to hunt now and stockpile its food for later. (And there are records of solifugids eating ants, but there are records of solifugids eating basically everything. Even lizards and birds.) But Cushing says there’s another possible explanation for this behavior.
Solifugids are prodigious diggers that usually only come out at night. (The word "solifugae" is Latin for "those who flee from the sun.") During the day, they like to hang out under rocks, cow patties or within underground burrows. “In the lab, I’ve seen them burrow down into the soil in such a way that you can’t even tell that there’s anything there,” says Cushing. And in fact, there are two more videos online of solifugids murdering ants where it appears the creatures are also doing some excavating to the opening of the nest.
So it’s possible that the animals aren’t interested in lunch at all and are merely seeking a place to cool off from the desert sun.
Interestingly, the fact that all three videos are shot in different locations—the first seems to be in Israel, and the others in India and the United States—means that whatever this behavior is, it’s widespread and being deployed by different species of solifugid. Ants of the world: Beware.
Keeping up with the Kalahari Ferraris
There’s a reason that another one of the solifugid’s common names is the Kalahari Ferrari: Solifugids are fast.
“A lot of arachnids are just sit and wait predators,” says Cushing. “And if they move, they move in short bursts.” Not solifugids. These tireless arthropods run and they run until they encounter a potential meal. Then they cut it apart with their bitey bits (known as chelicerae) and slather a bunch of enzymes into the wounds and suck out the sweet sauce it creates, and then they run some more.
“They have this incredibly high metabolic rate,” says Cushing. “They can move almost constantly, but because of that, they also need to eat a lot.”
Cushing recalls the time one of her colleagues working in the Negev Desert decided to see just how far a solifugid would run before it stopped. She gave up after two hours.
Of course, there is one thing that’ll stop a solifugid in its tracks: something edible. Even birds, lizards and small mammals can wind up as prey if they’re not careful to get out of the marauding solifugid’s path. “They just run into things, they really do,” says Jack Brookhart, a colleague of Cushing’s who studied on solifugids for decades.
While Brookhart is now retired and no longer in solifugid-chasing shape, he says in his younger days, he’d follow solifugids on foot as they zig-zagged across the desert at speeds of around 10 miles per hour. Then he would watch as they attacked whatever stood in front of them.
When a solifugid runs into something that moves, Brookhart says it rears up on its back sets of legs and immediately starts slapping the prey with its palps—appendages that look like legs, but are actually more like feeler organs. Interestingly, these palps have a sort of friction-based adhesive quality which allows solifugids to grasp their prey and climb smooth surfaces, like glass. “Like Spiderman might do to a brick building,” says Brookhart.
And once you’re in their clutches, it’s game over.
The better to inseminate you with, my dear...
The word “jaw” is far too simplistic to describe what’s in a solifugid’s mouth. Imagine if a scorpion’s claws were set up side by side in its mouth. And each of the four edges was equipped with an array of blades, teeth, and sensory organs. Some species can also rub their chelicerae together to produce a defensive clicking, called stridulation. All in all, a 2015 study of 157 different species of solifugid found that the arachnid’s chelicerae are composed of some 80 different structures.
And get this: In some species, the males’ chelicerae have tiny add-ons that scientists hypothesize are used for transferring sperm.
As with most solifugid biology, most of this remains in the realm of speculation. But if male solifugids do have sperm-transferring tools in their jaws, it would make a lot of sense. That is, if you know anything about the savage manner in which solifugids make love.
According to Jen Rowsell, who conducted solifugid mating trials as part of her master’s thesis at West Texas A&M University, it all begins innocently enough. The male approaches the female and caresses her with his palps. But as soon as the male touches the female, for reasons we don’t fully understand, she falls into a hypnosis-like trance.
At this point, the male begins to manhandle the typically much-larger female, tugging her to and fro. “It’s just honestly beyond awkward to watch,” says Rowsell.
Next comes the mouth stuff. The male plunges his jaws into the female’s genital opening and just starts going to town. The top part of the chelicerae, which as you now know are quite large, go all the way in to the hilt. “They create this incredibly violent back and forth motion, just like when they’re eating. The head pulses. They’re basically chewing on the female’s lady-parts,” says Rowsell.
Nobody knows for sure what all this macabre mastication accomplishes. Rowsell says it could be that the female’s reproductive organs need to be stimulated or prepared in some way. Or perhaps this is the male’s way of gouging out any other competitor’s sperm left behind from an earlier courtship.
After what must feel like an eternity to everyone involved—including the researcher—the male pulls out. At this point, males of some species press their genital openings against the female’s orifice briefly; others lay a sperm packet on the ground, pick it up and insert into the female with their chelicerae. Regardless of the species, this step is followed by still more gnawing away at the female’s genital opening. Again, we don’t know why exactly, but it’s thought this might help open the sperm packet.
This whole affair sounds horrific, which might be why the females have evolved a catatonic state to endure it. But there is a caveat. “If the male deviates in any way from the sequence, the female will emerge from her trance-like state with a hellfire inside her,” says Rowsell.
Once awoken, the female solifugid thrashes about until she can free herself from the male. Then it’s her turn to get bitey. Rowsell says she would usually intervene at this point, because adult solifugids are so hard to come by and she didn’t want to risk either animal ending up injured. But on a few occasions, the female would actually start eating the male.
Nature, it seems, is a double-edged solifugid.