It was long thought that all 40,000 species of spiders in the world were strict predators - feeding on other insects or animals. Now two researchers - Christopher Meehan of Villanova University, and Eric Olson of Brandeis - have revealed that a small Central American jumping spider is predominantly a plant eater.

The species, Bagheera kiplingi, lives throughout much of Central America and southern Mexico, inhabiting several species of acacia shrubs. A classic example long cited in ecology textbooks, these particular acacia plants have developed a co-evolutionary mutualism with certain ants. The ants fiercely protect the shrub from would be herbivores, while the acacias provide both housing for the ants via swollen, hollow spines and food in the form of nectar (excreted from glands at the base of each leaf) and specialized leaf tips known as Beltian bodies.

The Bagheera spiders cheet the ant-accacia system - actually stealing and eating both nectar, and Beltian bodies, all without helping to defend the plant. The spiders avoid ant attacks through 'active avoidance' - aided by excellent eyesight, agility and cognitive skills.

In the field, the researchers documented behavioral patterns through direct observations and high-definition video recordings. Herbivory was especially clear in the Mexican population: Beltian bodies accounted for more than 90% of 140 food items identified. According to Meehan, "This is the first spider in the world known to deliberately 'hunt' plant parts; it is also the first found to go after plants as a primary food source."

Release: http://www.eurekalert.org/pub_releases/2009-10/vu-hdi100609.php