thanks Babe. with knowledge comes power... Or something like that!
And GF, I did have a small tree growing next to my house that I removed last spring, and that seemed to get rid of the bugs for quite a while. But they came back, not quite as many as before but still quite numerous. A friend who's an arborist says the nearest box elder tree that she knows of is more than a block away. But who knows, I may have to go snooping in the neighbors' yards.
Growing up there was a huge very old box elder tree right on the fence-line between my house and my neighbors. Besides that my neighbor had all his firewood piled up right against the tree. Man, it was a firebug paradise. If I had wanted to I could have filled a 50 gallon drum by just scooping them up by the handful. Millions of them everywhere.