In slither.io, there are these little moving balls that glow. If you eat them, you grow more than just eating a regular food pellet. One thing about them that's kinda weird, is that if you move toward them they will dodge you.
For reference, here are some screenshots of them.
The purple on here:
and the violet one here:
What are these things? Are the controlled by other players? Do they have a name? What are some strategies for them?