The olfactory system directly interfaces with the environment, and thus changes in the environment or an animal's habits would presumably also lead to changes in the olfactory system. Comparative studies on specialized animals with known generalist ancestors could hence be a way of revealing general processes shaping olfactory systems as well as highlighting the importance and function of specific chemosensory genes. Drosophila sechellia, a close relative of D. melanogaster, and highly specialized towards the use of the toxic Morinda fruit, has been the subject of several studies aimed at pinpointing the consequences of host choice to the chemosensory system, from the molecular level to behavior. This paper highlights some recent (and not so recent) advances in this area and concludes with a brief discussion on the antiquity of the D. sechellia-Morinda connection.