Leaf-cutter ant
"Leaf-cutter ants are the major forest herbivores in Central America and consume more plant matter than all the vertebrate herbivores put together. Their subterranean nests can be vast and home to many millions of ants and they have a really neat defence system where minor workers ride shotgun on top of the leaf loads carried by the major workers and fend off the attacks of parasitic flies". George McGavin.