But when the unassuming caterpillar faces off against an uninvited interloper, it drums the leaves of war. The discovery upends the concept of caterpillars as leaf-munching milquetoasts. After hatching, each caterpillar spins a little silk tent on a leaf to keep out both predators and the elements while it eats its way around the neighborhood. Constructing these pavilions takes so much energy, suggests Yack in the Proceedings of the National Academy of Sciences, that they're worth defending against trespassers. If the intruder fails to cease and desist, the resident starts drumming its mouthparts as well, setting up a threatening vibration that usually sends all but the biggest outsiders packing.
Most contests last a few minutes, but determined defenders can keep it up for many hours.
Although silent to the caterpillars, which can't hear, the racket can be picked up by people 10 feet away. At Land Conservation Local and regional conservation groups in California have set aside 1.25 million acres of open land. In doing so, they have also set a record. For perspective, the amount of land is greater than the total area of Rhode Island, and nearly equal to the size of Delaware. In a related landmark event, all 50 states now contain permanently protected land.