Diagnosing the variability in prospective inter-specific interactions informs both our understanding of particular species as well as how the ecological complex of which they can be a part are altered by their presence. This study uses empirical field descriptions, complemented by published floras and the resources at centers for species conservation, to explore macro-ecological patterns in interactions between plants and ants. I describe on-plant foraging by ants on 70 plant species (11 families, 29 genera) in the Sonoran Desert region, highlighting particular combinations of plant species, ontogenetic stages, and season where forager visitation is disproportionately high or low. Through my plant-ant association surveys, I find species-specific descriptions of on-plant foraging: (1) are qualitatively similar among sites (an arboretum and a wilder location), (2) can predict the activities of ground foraging ants at the patch scale (plant neighborhoods of 12 m²), (3) show plant community types within the warm North American deserts have diverging likelihoods of on-plant foraging, and (4) brief inspections can describe among-plant variation in likelihoods of visitation by ants as well as herbivores that can be deterred by ants.