Walking on Water:
(sfx: thunderstorm) 

SPIDERS APPARENTLY HAVE A REPUTATION FOR SURVIVING STORMS. 
YOU KNOW WHAT I'M TALKING ABOUT. . . 

(SFX: "Itsy Bitsy spider") 

WHETHER OR NOT YOUR AVERAGE WEB WEAVER CAN REALLY SURVIVE
IN TORRENTS OF RAIN, THEY CERTAINLY HAVE ADAPTED WELL TO
WATER.  A NUMBER OF SPIDERS CAN WALK ON TOP OF LAKES AND
SWAMPS.  NOT JUST WALK ACTUALLY--THEY RUN.  SPRINT.  SKATE ALONG
SO FAST YOU'D HAVE TROUBLE KEEPING UP. IT'S A PRETTY AMAZING
FEAT--AND ROBERT SUTER HAS STUDIED HOW THEY DO IT. 

Suter: "In order to sit on top of the water and not fall through. . .they have to be
hydrophobic which means that the substance that their legs are made of reject water."

ALL WELL AND GOOD, BUT THAT JUST MEANS THE SPIDER WON'T SINK. 
SUTER IS A BIOLOGIST AT VASSAR AND HE SAYS THAT THESE
HYDROPHOBIC LEGS ARE KIND OF WAXY--AND THAT'S THE EXACT WRONG
THING FOR GATHERING SPEED. 

Suter: "The water is very slippery as far as the spider is concerned, so we've been trying to
figure out how . . . they can use this very slippery surface and still get going quite fast." 

SUTER CONSIDERED THE POSSIBILITY THAT THE SPIDERS MIGHT BE
DIPPING THE TIPS OF THEIR LEGS INTO THE WATER TO PUSH OFF AS A
SWIMMER WOULD.  BUT THE LEGS ARE SO THIN THAT WOULD BE A LOT
LIKE TRYING TO SWIM JUST USING ONE FINGER TO PADDLE INSTEAD OF
YOUR WHOLE HAND.  TO GET SUCH GREAT SPEED, THE SPIDER MUST
HAVE MORE PURCHASE.  USING HIGH SPEED CAMERAS TO TAKE FLASH
PHOTOS, SUTER DISCOVERED THAT THE SPIDERS GOT THE EXTRA DRAG
BY CREATING A LITTLE DIMPLE IN THE WATER. 

Suter: "IT'S very much like if you took a balloon and you put your finger down intot eh
surface of it, your finger doesn't go inside the balloon, it stays on the outside of the
balloon, but it causes a dimple."

THE SPIDER THEN USES THIS DIMPLE WITH ITS EXTRA SURFACE AREA TO
PUSH BACK ON THE  WATER.  THE DIMPLES ACTS LIKE A LITTLE PADDLE
AT THE BOTTOM OF THE SPIDER'S LEG, AND BY PADDLING ACROSS THE
VERY TOP OF THE WATER THE SPIDER CAN REACH ITS PHENOMENAL
SPEEDS.