White-lined Sphinx Caterpillar Invasion!

There are few hundred of these things that just suddenly appeared in my yard. They are everywhere. Apparently, they are the White-lined Sphinx, which every few years here, they come out in such quantity that they have caused road closures because of making the roads so slick. They just suddenly appeared, like they came out of the ground or something. Like a freaking zombie movie, but with caterpillars.