This time of year we often receive questions about ants crawling on peony buds. The ants are feeding on an exudate from the bud; they do not feed on the flowers themselves. The exudates is high in sugar and therefore a good energy source for the ants. The ants also seem to help protect the buds from other insects that would like to feed on the buds. This is a symbiotic relationship one in which a relationship between two organisms works to the benefit of both. The ant gains a high value food source, and the peony receives flower-bud protection. So if you see ants on your peonies, leave them be. They are not harming the peonies. (Ward Upham)
