Rostrum

A rigid tube extended from the head of certain insects or crustaceans. In crustaceans, curculionidae and some fish, it is a rigid extension of the head. In dolphins it is the beak or muzzle. In sucking insects and certain parasites, it is a mouthpart used to pierce and suck.
The term can also designate a mouth-piece that can pierce skin, and that can be used for sucking blood by certain insects and parasites.