  Collective behavior of active elements inspired by mass of biological
organisms is addressed. Especially, two topics are focused on among amazing
behaviors performed by colony of ants. First, task allocation phenomena are
treated from the viewpoint of proportion regulation of population between
different states. Using a dynamical model consisting of elements and external
``stock materials'', adaptability against various disturbances is numerically
studied. In addition, a dynamical model for a colony ants interacting via two
kind of pheromones is studied, in which simulated ants, as a mass, are shown to
make an efficient foraging flexibly varying the foraging tactics according to
feeding schedules. Finally, experiments are performed with robots moving in
virtual pheromone fields simulated by CG and CCD camera feedback system. Trail
formation processes are demonstrated by this multi-robot system.
