June 4, 2012 | 7
A spider has to work pretty hard to be considered almost cute, and one particular African desert spider is literally turning cartwheels to do it.
The golden wheel spider (Carparachne aureoflava) is a species native to the steep sand dunes of the Namib Desert in Southern Africa. It belongs to the huntsman family, which means it likes warm climates, does not build a web and is an extremely nimble hunter. Though only little, at around 20 mm in size, the golden wheel spider can build silk-lined burrows that extend 40 to 50 cm below the surface of the sand dunes, and with no web to snare its prey, will wander through the night in search of insects. Which of course makes it vulnerable to being preyed upon itself, particularly by its archnemesis, the parasitic Pompilid wasp.
Also known as spider wasps, Pompilids are a family of large, strong, solitary-living wasps who have a tendency to prey on spiders, sometimes even bigger than themselves. They can sniff out a golden wheel spider in its burrow, and can shift up to 10 litres of sand – that’s equivalent to 80,000 times its own body weight – to get to it. The wasp will then paralyse the spider with its venomous stinger, before dragging it into a burrow and laying a single egg in its abdomen. The spider and the egg will be sealed in the burrow, and when the egg hatches, the larva will have an enormous supply of food waiting for it. Severely paralysed but not yet dead, the spider will be eaten alive from the inside out.
Understandably, the golden wheel spider will go to great lengths to ensure that it doesn’t become a living nursery for a Pompilid larva, and has developed one of nature’s most remarkable modes of escape. Taking advantage of the steep slip-faces of the dunes it lives on, when threatened, the spider will curl its legs around its body to make a ball and roll down the slope to safety at speeds of 1 m/s and about 20 rotations per second, according to the research of entomologist Joh Henschel from the Gobabeb Training and Research Centre in Namibia. You can watch a video of the spider cartwheeling here.
While spiders in the Carparachne family are the only known ‘wheeling’ spiders, wheeling behaviour can be found in a handful of other animals, including the larvae of the southeastern beach tiger beetle (Cicindela dorsalis media), the American mantis shrimp (Nannosquilla decemspinosa) and caterpillars of the moth species Pleurotya ruralis and Cacoecimorpha pronubana. In 2011, biologists, Alan Harvey and Sarah Zukoff, both from Georgia Southern University in the U.S., published a paper in PLoS ONE documenting the first observed case of wind-powered wheel locomotion in the common species of southeastern beach tiger beetles.
The pair conducted field studies in 2007 and 2010 on the southeastern shore of Cumberland Island National Seashore in Georgia. They collected larvae from the mouths of their burrows, placed them on the surface of the sand, and gently provoked them until they displayed either death feigning – contracting the body and regurgitating – or wheeling behaviour. If a larva chose the wheeling defense mechanism, it would start leaping into the air, loop its soft, wormlike body into a rotating wheel and either ‘hit the ground rolling’, or leap again. Harvey and Zukoff also observed that the direction the larvae would wheel in is closely related to the direction in which the winds were blowing at the time.
All of the larvae the researchers observed wheeled in an up-slope direction, because the winds were always blowing from sea to land in an upwards direction. Stronger winds were able to carry the cartwheeling larvae up to 60 m away from where they were provoked. A frame-by-frame inspection of 48 high-speed video clips revealed that the larvae were travelling at speeds of 3 m/s – faster than the researcher’s assistant could run after them on the sand, and one of the fastest speeds recorded for an insect on the ground. “Our slow-motion videos showed that they were actually making carefully timed leaps that became these beautiful aerial somersaults, which seemed to let them orient to the breeze and then ‘hit the ground rolling.’ We almost couldn’t believe our eyes,” said Harvey, of what could easily be described as the larval version of the Tiny Wings bird. Once the wheeling slowed down and stopped, the larvae would uncoil, and either crawl away or burrow into the sand to safety.
Interestingly, the researchers suggest that this behaviour, just like the golden wheel spider’s, has come about in response to the parasitic wasps that hunt them.
With a skill like this, Golden Wheel Spider is never going to be anything but the class clown, which is kind of okay when you’re actually in school and anything that stops you having to do work for even a few minutes is very funny, but when it’s time to be an adult, there’s pretty much no reason for you to ever do a cartwheel, unless you’re some kind of hippie street performer. Which means Golden Wheel Spider is going to wear awfully thin in your average work environment.
He’ll try being a waiter at his local Chinese restaurant like, “Okay, so wonton soup, Peking ribs and Szechuan prawns? Got it,” and then cartwheel back into the kitchen, crashing into a huge wall of pots and pans. The chef will hurl a bottle of oyster sauce at him.
“That wasn’t even funny,” the diners will remark, and will be even less impressed when they discover that Golden Wheel Spider forgot their Peking ribs because the sauce bottle blow to the head knocked a third of their order right out of his brain.
So Golden Wheel Spider will try being a sales assistant at a women’s clothing store like, “Is everyone okay for sizes in here? You need an 8 in the red? Okay I’ll be right back.”
And he’ll be right back with an 8 in the red and the customer will be like, “Why is it all torn up? I don’t want this,” and Golden Wheel Spider will tell her it got caught around several of his legs as he cartwheeled over to the change rooms but it’s mostly fine.
“Why did you have to cartwheel over here in the first place?”
“Because it’s hilarious. Can I get you a coat to try on?”
The worst is when Golden Wheel Spider will try working at an advertising agency all, “And then the family sit down to a lavish Christmas dinner because they’re safe in the knowledge that they now have a funeral plan in place.”
“Tasteful. I like it,” the clients will say.
And then the Golden Wheel Spider will shake their hands and cartwheel out of the room with gusto and the clients will pull out of the deal once they get back to their office because funeral plan brokers may have a sense of humour, but there’s nothing funny about a spider who tries too hard for the lols.
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