Scientists have discovered the world’s first known vegetarian spider.

Bagheera kiplingi, a Central American species, lives almost exclusively on leaf buds and is thought to be the only spider of about 40,000 species to have rejected a carnivorous diet.

Instead it has developed a laidback lifestyle based on nutritious wild acacia plants — and has no need to spin a web to catch its prey.

“This is the first spider known to ‘hunt’ plants as a primary food source,” said Christopher Meehan of Villanova University, in Pennsylvania, who observed the creatures, about the size of a thumbnail, on a field trip in Mexico.

The vegetarian diet of B kiplingi may be connected with other changes. Since it no longer needs to go through the energy-sapping business of catching prey, it has diverted its web-spinning abilities to building family homes. Mothers use the nests to rear their young.

B kiplingi does not, however, lead an entirely blameless lifestyle. Its food may be vegetarian but the spiders first have to steal it from under the noses of the ants that guard acacias against invaders.

For zoologists, though, the most startling aspect of Meehan’s discovery is that spider physiology was thought to make plant-eating impossible.

Times Recommends

• How I lost the gift of joy for a while
• Why Ann Widdecombe has got it wrong
• Alas, it’s the end of the road for petrolheads