This video from the USA says about itself:
21 July 2016
Salt-marsh Caterpillars on the move in their true natural environment. Often a pest when they invade cropland, here they are in the vast and remote St. Johns Marsh of Florida. Preferring broadleaf plants to grasses these caterpillars are searching for better food and the 25 mph winds are not helping them any. They develop into rather large white moths with small black dots.