Over the past 40 years there has been an extraordinary effort to understand the relationships of plant-feeding insects and their hosts. Anyone who is studying such problems knows the mountain of literature which must be scaled. Perhaps 10% of the papers in journals such as Ecology consider phytophagous insects; in more specialized journals, such as Journal of Chemical Ecology or Journal of Economic Entomology, the figure is much higher. Moreover, the production of such research shows no sign of deceleration. Despite all this effort, we have collectively developed only a skimpy theoretical framework with which to understand insect diet breadth or plant defense strategies (for example). We will argue that new developments are certainly needed. If theory is the mainspring for our research programs, then we might indeed consider a drought alert.