At any given instant the four bugs form the corners of a square which shrinks and rotates as the bugs move closer together (see the illustration). The path of each pursuer will therefore at all times be perpendicular to the path of the pursued. This tells us that as the Green bug, for example, approaches the Yellow one, there is no component in the Yellow bug's motion which carries the Yellow toward or away from the Green. Consequently the Green will capture the Yellow in the same time that it would take if the Yellow had remained stationary. The length of each spiral path will be the same as the side of the square: 10 units.