What’s eating my Leaves

Hi all,
Having a walk around the fruit trees this evening and noticed the leaves on one of our Cherry trees was missing a lot of leaves and a fair number had been on somethings supper menu. Had a good look with my aged eyesight and noticed some black dots that didn’t move and a lot of ants. Any ideas what could be dining out on the Cherry foliage? Surely not ants...
Regards