Peony buds always seem to attract a number of ants.
I think this is Formica subsericea
Either there are numbers of ants or there are numbers of other insects–often flies.
These peonies had a number of very colorful bluebottle flies, probably Cynomya species. I suspect the flower secretes a sugary substance that attracts the insects. There is probably some kind of biological function to that secretion, but I am at a loss as to what that function would be.