These are tightly grouped as they have been since they hatched. The eggs are laid in clusters, the caterpillars stay together and then pupate in groups. These have been protected in a cage for almost their entire life cycle. Unlike when they're exposed to predation, 14 out of 16 hatchlings survived to chrysalis. In the wild it's probably less than 5%. Note the tethers looped around the wire they attached to.