Spiny Spiders Use Colors to Lure Lunch

ByABC News
June 18, 2002, 1:44 PM

June 20 -- While studying animal behavior in the rain forest of northern Australia, Mark Hauber couldn't help but notice spiders with brightly colored stripes on their bodies that stood out like neon warning lights. How, he wondered, could they catch lunch?

It was intriguing to the Cornell University researcher because normally spiders need to blend into the background as they lay in wait for some unsuspecting insect.

"They were really conspicuous," Hauber says.

These spiders went to all the trouble of building an inconspicuous web, and then they stand out in the middle of the web as a "really bright spot," he said. "It just doesn't make any sense."

Hauber, a researcher in Cornell's Department of Neurobiology and Behavior, set up a simple experiment to figure out what the spiny spiders (Gasteracantha fornicata) were up to. Although other research and even common sense indicated that members of the animal kingdom use color to attract a mate, or blend in with the background, these critters were using color for an altogether different purpose.

Color, says Hauber, was part of the trap. They use color to lure in their lunch, and that's believed to be very rare in the animal world.

Looking Pretty for Lunch

It's not clear yet just why it works, but Hauber suspects that to the unwary insect, the spider looks like a flower, not a bloodsucking carnivore.

But bright colors would also alert other predators, like birds and spider-eating mammals, to the presence of the spider. Having a bright stripe running down your back is not exactly a good thing if you're trying to hide from something else.

But it apparently works for the spiny spider, Hauber argues in a report in an upcoming issue of the Royal Entomological Society's journal, Ecological Entomology, because birds and other predators have learned that it's not worth the effort to try and eat one of the little beasts.

The spiders have a hard crust with spines on both sides, "so it's hard to chew and not really easy to eat by a predator," he says. "So it can be conspicuous, and once it's conspicuous, it can use that color to attract the insects."