Large Black Ants in Oak Tree

[kingbee]

I have several large oak trees that I`m working on,and noticed that there are bunches of large black ants working in and out of a couple of the trees(they seem to be partially hollow)and a friend located next to me just lost a large oak,and he said it was full of these same ants.Should I try to kill these ants,and would putting a ant killer aroud the tree harm it?Any suggestions?Thanks,Kingbee...