Insect herbivores are one of the most diverse lineages on the planet, with an estimated 1-5 million species; our recent work has uncovered an unprecedented level of convergence at the molecular level across 300 million years of insect evolution (in butterflies, beetles, bugs, and flies). It appears that to eat toxic plants, specific genetic substitutions are almost always needed in toxin-resistance genes. Our approach is now poised to answer big questions regarding convergence. We propose to address the hierarchy of convergence spanning DNA sequences, physiology, and behavior and will test key hypotheses about the impacts of convergence on the diversification of species. Where organisms have not converged at all levels, we will ask if those linages are less diverse and whether they use alternative strategies? In total, our approach is to provide a highly general evaluation of the causes and consequences of convergence, which could reshape our understanding of, and approach to, evolutionary biology. By assembling a team at three premier universities ready to conduct behavioral and physiological assays, phylogenetic modeling, and transgenic approaches, we are well positioned to tackle these broad-reaching questions. We will produce numerous (>10) research publications to be targeted at the most prominent general science venues; in addition, we propose to lead a symposium at an international conference and to communicate our most general findings in a synthetic article for the public. Our findings and synthesis will not only impact the thinking of biologists, but have the potential to inform how we understand “chance” and “determinism” in the history of life. Because our work is based on replicated evolutionary events, on understanding the causes and consequences of convergence, and spans behavior, physiology, and genetics, we have the opportunity to forge a novel way of thinking about the meaning of convergence.