Aww, now I get it. I've heard of De Havilland, but never heard the Gypsy Moth name. Cool plane, bet it was a blast to fly.
It doesn't kill the trees ?
We've had them before, like oldsmokey stated, back in the 80's. But they were killed off by a wet and cold spring.
I've been told, most trees can handle 2-3 years in a row of them before it will kill them. A lot of the trees re-grew leaves last year, but they were smaller.
I should have greased my trees earlier than I did, but was lackadaisical.

When the little bugger's hatch from the cocoon, they go to the ground and climb back up. I waited about 1-2 weeks after they hatched, so a lot got in the leaves.
They come down at night and have to climb back up. Not all of them at once, but I think they all do at least once.