Tree Mystery

During our walk this evening, we came upon this tree. The things that look like worms are actually little tubes of sawdust. A careful look at the ground shows more piled there at the base of the tree. The tree, by the way, is completely dead and has been so for at least a couple years.

Neither one of us recognized this strange sight and we're wondering if anyone out there in Blipland might know what they are. Blippers?