This interrupted case study examines the evolution of cricket stridulation in the Hawaiian Islands, where a silent, non-stridulating phenotype of Teleogryllus oceanicus has evolved and spread throughout Hawaiian populations in just over a decade in response to predation by a parasitoid fly that finds crickets to prey upon via their calls. Students learn how natural selection works and use simple Mendelian crosses to uncover the genetic mechanism driving the change. Finally, they are introduced to the most recent development in this evolutionary case study, the appearance of a new phenotype that produces a purr-like call. Students evaluate data that tests the hypothesis that this new call is more attractive to female crickets than the silent phenotype while still avoiding predation by the flies better than the ancestral call type. Originally designed as a review of natural selection fundamentals and hypothesis testing for an undergraduate course on animal behavior, it is similarly suited for courses in evolution, ecology, introductory biology, or advanced high school biology.