Let fly a dragonfly!

Ever roving near a river or a pond, watching a dragonfly staying at one place, and then, suddenly, popping up just nearby? Actually, the dragonfly is not staying at one place. It's moving toward you, yet in the way, that you perceive it stationary.

Even when moving, most animals
have a good sense of the direction to a given fixed object at any time,
and expect to see it on that line. If the aggressor moves so that at each
moment it is on the line between the target and a given fixed point,
which could be its initial position, then its relative motion in the eyes
of the target is the same as that of the stationary reference point. The
only way that the target can know that it is not stationary is to notice the change in size of the aggressor as it approaches.

Look here to read a more understandable (i. e. with a picture) description.
Fascinating :-)