Yellownecked Caterpillars are a type of gregarious caterpillar, one of the more disgusting elements of summer

Pat found these on a Chinese Castanea across the road from the entrance to China Valley. They had completely stripped the foliage from a 3' branch on the ~15' tree. Gregarious caterpillars hatch together and stay together feeding in bunches. Some sort of "collective awareness" allows the to move as one in response to various stimuli. It is curious to see them moving their bodies and heads together as though choreographed. Kind of spooky actually.