The heart-shaped face of this ant soldier of the Atta laevigata species allows room for muscles that power her scissorlike mouthparts. While she stands ready to bite attackers, other workers use equally impressive mouthparts to slice up leaves to nourish their gardens of edible fungus.
Ancient ants developed farming some 50 million years ago, long before people, says Ted Schultz of the Smithsonian Institution in Washington, D.C. (Bark beetles and termites also farm.) Schultz and Smithsonian colleague Seán Brady used DNA and ants in amber to trace the farmer-ant family tree. The leaf-cutter lineage is surprisingly new, arising 8 million to 12 million years ago, but leaf-cutters became dominant plant eaters in their tropical ecosystems, the researchers say in a paper published online March 24 in Proceedings of the National Academy of Sciences.