This thread went sideways! Nobody is going to 'capture' forest tent caterpillars and release them into another location!
DH and I got as many as we could by cutting them out of the trees. We must have seen them just as they were coming out of the nests, as they were gathered in huge clusters. We feel we removed (and burned them -sorry folks but they are vermin) the majority of them.
The trees lost minimal foliage and look lovely.
Thanks for all the advice.