The noctuid genus Helicoverpa (Hardwick 1965) is one of the most widely studied groups in the Lepidoptera. This genus contains several of the world’s major pests of agriculture. However, most of the species in the genus are characterized by limited geographic spread and narrow host plant ranges, making it a valuable model system for studies in the evolution of generalist phytophagous insects displaying the central characteristics of pests: fecundity, vagility, and polyphagicity. How the tools of modern molecular biology are being applied to species in this genus to address fundamental issues such as these will be the theme of this review.