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MIKE PESCA, host:

This is DAY TO DAY I'm Mike Pesca.

MADELEINE BRAND, host:

And I'm Madeleine Brand. And now a story Spiderman would love. Scientists have discovered a tarantula that shoots webs from its toes.

NPR's David Malakoff reports.

DAVID MALAKOFF: The discovery that the toes of the Costa Rican Zebra Tarantula have comic book powers was a bit of a fluke.

Professor ADAM SUMMERS (University of California): The bizarre result came about in the most wonderful of serendipitous ways.

MALAKOFF: Adam Summers is a biologist at the University of California in Irvine. He's on the tarantula research team and he says a technician working with Stanislav Gorb of the Max Planck Institutes in Germany was making tarantulas walk across glass plates. He was studying how spiders get traction. And when the technician wanted to take a break he'd simply tilt the glass up at an angle.

Prof. SUMMERS: Tarantula spiders are quite worried about falling. And so if you tilt the glass up, they'll stop and they'll adhere with all eight legs as hard as they can; and this is actually an easier way to immobilize a tarantula than to pick it up and put it back in its cage and then go on your break.

MALAKOFF: One day, the technician came back from his break and noticed something unusual.

Prof. SUMMERS: The tarantula had slid backwards. All eight legs had slid and at the tip of each foot you could see an array of tiny pieces of silk - silk production from the completely the wrong end of the animal.

MALAKOFF: The strands of toe silk are tiny, almost invisible, which is why nobody noticed them before. But Summers said they clearly help the spider keep its footing. And the toe silk may provide hints about spider evolution. It could be he speculates...

Prof. SUMMERS: That what we're seeing in the tarantula feet is the most ancestral use of silk. That is silk evolved as a gluey adhesive and it became elaborated into the seven different kinds of silk that a spider might produce.

MALAKOFF: The tarantula study appears in the current issue of the journal Nature.

David Malakoff NPR News.

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