Behaviorally plastic host-plant use by larval Lepidoptera in tri-trophic food webs

• Caterpillars show plastic behavioral responses to plants and carnivores.
• These behavioral responses include diverse feeding and movement tactics.
• Behavioral plasticity of herbivores plays an active role in plant–insect interactions.
• Adaptive plasticity in herbivore behavior may stabilize populations and communities.

Plant–insect interactions research emphasizes adaptive plasticity of plants and carnivores, such as parasitoids, implying a relatively passive role of herbivores. Current work is addressing this deficit, with exciting studies of behavioral plasticity of larval Lepidoptera (caterpillars). Here I use select examples to illustrate the diversity of behaviorally plastic host-plant use by caterpillars, including anti-predator tactics, self-medication, and evasion of dynamic plant defenses, as proof of the agency of caterpillar behavior in plant–insect interactions. I emphasize the significance of adaptive behavioral plasticity of caterpillars in the context of tri-trophic interactions. Recent research on trait-mediated indirect interactions places adaptive behavioral plasticity of herbivores at the center of community and food web dynamics, with far-reaching consequences of issues such as community stability.