Substrate silking –  Caterpillars spin copious quanities of silk as they move over the branches of their host plants. The silk of some species contains a pheromone which channels the movement of the colony as th ey move from place to place. In other species, a trail pheromone is secreted independently of the silk.  In either case, a primary function of the silk appears to be that of enhancing steadfastness as the caterpillars move over the smooth surfaces of the host plant