Fox 254

http://www.8foxes.com/

This is just a model for a very basic structure in Organic Chemistry. Real molecules are more dynamic than this. Atoms vibrate even at very low temperatures.

Fox 240

http://www.8foxes.com/

Now this asks little more than geometry.

Note that the random process described in the question is discrete.

Ladybugs "appear" in next vertices at the same time.