Others will manufacture their own insect repellant, which in many cases is the bit of the plant humans most enjoy—it’s the rich oregano oil in oregano, the sharp spice in a horseradish root. Sometimes the approach is more sinister. One devilish case has been found in the humble tomato: the tomato plant will inject something into its leaves that makes the caterpillars look up from their chewing and turn to eye their fellow caterpillars. Soon, the leaf becomes irrelevant. The caterpillars begin to eat each other.
