Caterpillars are excellent model organisms for understanding how multiple selective forces shape the ecology and evolution of insects, and organisms in general. Recent research using the tools of modern molecular biology, genetics, metabolomics, microbial ecology, experiments conducted at a global level, network analysis, and statistical analyses of global data sets, combined with basic natural history, are yielding exciting new insights into caterpillar adaptations and ecology. The best way to view these research advances is within a framework of tri-trophic interactions. This is a timely...