Fruit fly species residing in the Sonoran Desert of North America are faced with a suite of ecological challenges. The desert is extremely hot. The resources that the flies use to feed and breed are toxic to many organisms. These flies are able to flourish in such an inhospitable place because of adaptations at many biological levels, from their metabolic chemistry to their mating behaviors. Understanding the nature of these adaptations has broad implications for all organisms, especially under conditions of global warming and habitat disturbance. The work to be undertaken during this 5 year project will explore certain components of the ecology and population biology of these insects: their ability to withstand heat stress, their longevity, temporal and spatial qualities of their abiotic and biotic environments.