Vegetarian spider discovered

12 October 2009 08:32pm

Scientists have discovered the world's first vegetarian spider - which steals food from acacia trees under the noses of watchful ants protecting the plant.

The neotropical jumping spider Bagheera kiplingi is the only one of 40,000 known species of spider to survive predominantly on plant food.

Unlike all other spiders, which use webs or direct hunting tactics to catch insects or even birds and lizards, this species concentrates on outwitting the ants which live on acacia trees in Mexico and Costa Rica to get to their food.

The trees and ants have evolved together, with the plant providing housing for the insects in hollow spines and food in the form of nectar and specialised leaf tips known as Beltian bodies, in return for protection of its leaves against animals looking to snack on them.

The research, published in the journal Current Biology, revealed that the Beltian bodies are the main food source for the spiders, who "cheat" the system by taking the plant food without doing anything to protect the tree.

The spiders, which are almost entirely vegetarian in Mexico but supplement their diet with prey including ant larvae more often in Costa Rica, dodge the acacia ants as they patrol the plant to defend it against attack.

The scientists, led by Christopher Meehan of Villanova University and Eric Olson of Brandeis University in the US, said the spiders used excellent eyesight, agility and cognitive skills to avoid the ants - as well as possibly mimicking them and their chemical scent.

Mr Meehan said: "Jumping spiders in general possess incredibly advanced sensory-cognitive skills and eight-legged agility, and Bagheera is no exception.

"Individuals employ diverse, situation-specific strategies to evade ants and the ants simply cannot catch them."

Being vegetarian may also have influenced other social habits of the species, with hints that the males help to care for eggs and young - a tactic which is virtually unheard of among spiders, the researchers said.

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