Spider eats trees, not bugs: small jumping species steals lunch from ants.
Bagheera kiplingi belongs among the big-eyed, athletic predators in the family of jumping spiders and gets its name from a panther in a Rudyard Kipling story. Yet a population of these spiders in Mexico mostly eats bits of acacia trees, says Christopher Meehan of Villanova University in Pennsylvania.
A few other species do taste vegetable matter now and then, says Yael Lubin of Ben- Gurion University's Sede Boqer campus in Israel. Male crab spiders will sip nectar for a little energy boost. And some baby spiders eat spores that have stuck to a web. But on hearing about spiders specializing in stealing vegetarian food, "I was absolutely floored," Lubin says.
These arachnid herbivores are no wimps. "The tree is full of biting, vicious ant guards" Meehan said August 11 at Cornell University during the 12th International Behavioral Ecology Congress. The spider spends its life dodging patrols of ants to steal their (vegetarian) lunches. The spiders perch on leaf tips and nest in mature leaves, which are less heavily guarded.
Acacia trees and their resident ants are a textbook example of a mutually beneficial partnership. Tree thorns grow swollen bases that shelter ants. Glands at the base of the leaves ooze nectar for refreshment, and leaflet tips sprout nubbins rich in protein and fat. In defending their homes, ants rid the trees of invaders that might chew the trees.
Meehan, along with his Villanova colleague Robert Curry, watched videos of 140 spider meals. The researchers counted 136 acacia protein-fat snacks with a few nectar sips. On four occasions the spiders turned to meat, tugging ant larvae away from a passing nursemaid and eating the youngsters. But concentrations of a heavy form of nitrogen in spider tissue suggest meat moments don't happen often.
In Costa Rica, Eric Olson of Brandeis University in Waltham, Mass., found that this spider also frequents acacia trees and specializes in stealing ant food.
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|Date:||Aug 30, 2008|
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