Tiny Telephones.

LiveScience is on the line with a call about insect telephones. Please hold – this plant is busy:

When a subterranean insect takes up residence below a plant, it settles in to feast on the plant’s roots. In order to alert leaf-eating insects of the “no vacancy,” the underground insect sends a chemical warning signal through the plant leaves, so the leafeaters are alerted that the plant is occupied.