Well really mouth I suppose. This truebug has just captured its prey - a sawfly larva - with its lethal weapon.
The insects that experts call bugs have many different body shapes, sizes and colours. However, the one thing they all have in common is a long slender beak shaped mouth part that looks like a straw. They use this beak to poke through plants and occasionally animal skin and suck out sap or blood.
Canon EOS 7D