We have two different peonies in our garden planted right next to each other; either different species or varieties. The flower buds on one of them is currently covered in black garden ants Lasius niger, which are clearly attending them for some reason. The other peony has no ants - not one - on the flower buds.
I spent some time yesterday watching and photographing the behaviour and still can't explain it. There are no aphids, so it can't be honeydew, and I can't see any obvious extra-floral nectaries. The ants' attentions seem to be focused on the sides of what are probably sepals but may be developing petals (see photo).
|Lasius niger on garden peony © M. J. Lush, 2013|
Is this familiar to anyone?