This group was collected September 4th from Medfield MA, but many such groups were found throughout August and the first part of September wherever Greenbrier was present. These caterpillars rest quietly on the underside of larger leaves during the day, but when they are disturbed they will first undulate their bodies in unison and then, given further prodding, leap of the leaf and hang in mid air. A group of over 150 early instars diving off a leaf together is quite a sight!