What is the bald faced hornet's mouthpart used for?

The 'mandibles' are used for manipulating food into position and the first steps of mastication.

The 'maxilla', beneath the mandibles, also help manipulate food and are used to tell the characteristics of potential food.

The 'labium' is essentially the floor of the mouth, formed from two sets of secondary maxilla, it also helps manipulate food during mastication.

The 'hypopharynx' is a glob like structure that assists in swallowing.