What a find! These demonic looking caterpillars drop down from the trees to find a place to burrow & pupate in late summer.
If you look closely, you'll notice this isn't the same one as the first two photos. This one has black horns, I found him last August whereas the one with orange horns I found yesterday.
Maybe the larger, light teal with orange horns one is female and this one is male? I wonder...