What is this?

[Black Comb]

Thanks to everyone who replied.
I don't think it's a mouse because it's so symmetrical.

Anyway, mouse guard will go on just in case.

 

[beebreeder]

I would think twice about a mouse guard this early, thay can pull pollen from bees legs as they go through and generally the entrance block comes out and the mouse guard goes on and at this time of year that gives the bees an enormous area to keep wasps out