You probably have some winter kill with the bad winter that the eastern part of the continent experienced with many people reporting dead branch tips and 'sickly looking' slow to leaf out trees.

The ant are 'tending' to the aphids (little green bugs that feed on sap from the tender new growth). The ants actually harvest the sweet 'honeydew' that the aphids secrete. Nothing that will harm the tree if this stays in moderate numbers. On a smaller tree, you can take a water hose and wash them off for a while and on a larger tree good driving rain will slow them down but this is pretty normal occurrence this time of year an not much of a concern.

Honestly, I didn't see the bug in the last pic until I looked again. I just went by the 'aphid' comment in the original post. Didn't know there was a 'honeylocust plant bug'. Thanks Dave!

Honeylocusts grow late into the season, then that tender growth gets killed over the winter. That's just what they do. I don't see any major problems w/yours, tho aphid infestations don't do it any good, obviously.