|Some years, I've seen flower buds so full of ants, you could hardly see the bud.|
This is a common occurrence. I have heard there is a direct correlation to buds opening because the ants eat the sappy, sugary coating that the bud petals exude. Not sure this is the case, as I've seen peony buds open successfully without ants on them (for example, at the garden centre). At any rate, it's VERY common and the ants don't harm the flower buds.
|Photo from years ago... sniff, sniff - my old garden.|