Population Regulation in Insect Herbivores—Top-Down or Bottom-Up

Recent evidence points to the plant's being a much more limited resource than previously expected. In addition to the restraints on feeding and population growth imposed by such factors as leaf toughness, the physical environment, plant nutrition, etc., recent work points to the role of feeding- induced chemical changes in the leaves in reducing herbivore 'fitness'. This suggests that population regulation in herbivores may indeed sometimes be from the trophic level below that of the herbivore—the plant itself.