Green 1/4 inch worms
The leaves in the picture don't appear to be maple or pine. However, There are a number of moths that feed on pine trees. Is there any damage to the pines and if so, is it concentrated near the top or is it sporadic? If you have a more focused photo of the caterpillars, that would be helpful too.
I'm not certain what type of moth this will turn into. By the time caterpillars reach this size, most insecticide applications are not effective.
Sorry for the confusion. I now believe we have two species. The ones pictured on the milkweed leaves are milkweed moths. The ones cocooning on my grape leaves are the ones I am questioning. They are also in the oaks, Maple’s and pines. They are coming out of the trees on silk lines.
The white things on the pines do not have the feature of any insect I'm familiar with. It's possible they are immature slugs or a type of fungus. The maple photo is also one that stumps me. It might be the cocoons of a small moth.