When I pulled out my plastic bottom board yesterday, I saw something similar to this. In addition, I found worms in the sawdust/chaff. They were whitish in color and ranged in size from 10 mm to about about 2 cm. They looked like the wax worms I feed to my gecko.
I killed as many as I could, cleaned the board and sprayed it with Pam. Now I'm going to do a mite count.
I'm concerned for my bees :shock: