Enlarge (credit: Tobias Lortzing) Nature is, it’s often said, red in tooth and claw. But sometimes a claw scratches someone’s back in return for a symbiotic scratch of one’s own. Ants provide many examples of such mutually beneficial arrangements. As weird as it sounds, drinking the “blood” of a wounded bittersweet nightshade plant appears to be one of them. Ants and plants are often good friends (leafcutters aside) because ants prey on insects that munch on the plants.