Plants are attacked by myriad herbivores, and many plants exhibit anti-herbivore defences. We tested the hypothesis that induced defences benefit tomato plants by encouraging insects to eat other members of their species. We found that defences that promote cannibalism benefit tomatoes in two ways: cannibalism directly reduces herbivore abundance, and cannibals eat significantly less plant material. This previously unknown means of defence may alter plant–herbivore dynamics, plant evolution and pathogen transmission.
Comments from E. Preisser and E. Damschen greatly improved the manuscript. We appreciate artwork by B. Feeny. J.O. was hosted by the Department of Biology at Virginia Commonwealth University (VCU) while writing the manuscript; VCU Biology, the Johnson, Vonesh and Damschen laboratories kindly shared space and equipment for conducting experiments.