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Page last updated at 09:27 GMT, Thursday, 8 July 2010 10:27 UK
Camel spiders are sticky killers
By Matt Walker
Editor, Earth News


Camel spider versus cricket: will it come to a sticky end? (video courtesy of Dr Rodrigo Willemart)

Camel spiders have evolved a unique way to capture their insect prey.

The arachnids catch insects by sticking to them, using adhesive patches on the ends of their pedipalps, tube-like organs on either side of their mouth.

The technique is unusual among arachnids; scorpions use pincers to subdue prey while most spider use webs.

Scientists made the discovery filming camel spiders in slow motion, which revealed how they stick to crickets before tossing them into the air.

Details of the sticky killing technique are published in the Journal of Ethology.

When I watched the video I could see in detail how the cricket was being caught in the air by the suctorial organ
Dr Rodrigo Willemart

Camel spiders, of which there are hundreds of species, are unusual-looking arachnids.

Also known as sun scorpions, or wind spiders, they are not true spiders but members of the solifugids, a group of arachnids related to spiders, scorpions and mites.

Around the time of the Gulf War in 2003, they became the subject of wild and unfounded rumours, with soldiers telling tales of encountering supposedly large and bloodthirsty camel spiders in the desert of Iraq.

In reality, camel spiders do not grow beyond 12cm in leg span.

But they are adept hunters, preying mainly on insects and occasionally small reptiles and mammals, such as lizards or rodents.

Camel spider (Eremochelis bilobatus)
A camel spider awaits its prey

More unusual though, is the unique adhesive organs on the tips of their pedipalps.

Some camel spiders are known to be able to use these organs to stick to, and climb, vertical surfaces such as walls, although it is unlikely they climb much in the wild, where they tend to cover sand and prefer to hide under rocks.

Anecdotal observations have also suggested that they strike at or try to grasp prey with their mouthparts, but the action happens too fast to be certain about how they capture their victims.

So Dr Rodrigo Willemart of the University of Nebraska in Lincoln, US and colleagues based in Ireland and the UK decided to use high speed video to record the action.

They collected two adult male and one adult female of the camel spider species Eremochelis bilobatus from the wild at the Pawnee National Grassland of Colorado, US.


They then placed each into an artificial arena in the laboratory and filmed them attempting to catch different species of cricket.

In all, the researchers filmed at high speed 27 prey capture sequences.

Slowing the video down revealed that camel spiders attack prey with their pedipalps, using the sticky pads on the end to catch them.

"When I watched the video I could see in detail how the cricket was being caught in the air by the suctorial organ," Dr Willemart told the BBC.

"You don't see a thing at normal speed."

He says the discovery helps reveal how arachnids have evolved different strategies to solve the same problem of capturing fast moving prey.

"Whip spiders, whip scorpions and scorpions usually have strong pincer-like appendages to capture prey," says Dr Willemart, now at the University of Sao Paulo in Brazil.


"Spiders lack such pincers and use webs or adhesive hairs on their legs to get a hold on their prey, with spiders biting their prey after they have got a grip on it."

Now we know that "some species of camel spider, which also lack such pincers, use an adhesive structure to capture prey."

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