Surprise, surprise, surprise!  Looks like we have a crop of mushrooms growing in our worm bin.  After doing a little online research, it appears that mushrooms are not harmful to this vermicomposting process and is evidence of a healthy microfungal system.  If you have differing information, would you be so kind as to comment below.  In the meantime, we will just allow our worm friends to munch on this occasional snack.