Originally posted by WPRESTO Some places the trees are clean, other places such as this it seems that every tree has at least one = Gypsy moth egg cases. Either the same sort of tree attracts them, or once one of them lays eggs at a particular spot, it attracts others.
The females of the subspecies we have in North America can't fly, so they pretty much lay wherever they are. The caterpillars will roam though, and can float on the wind with all their hairs, so they can disperse this way. They are adaptable, but I think oaks are their favourite food, and if they are somewhere happy a batch of caterpillars may spend their whole life on one tree and pupate en masse at the base.
I've posted it in these forums before, but not this thread, here's a gypsy moth caterpillar from a few years ago: