It has special structures on its back to hold debris and corpses, this disguises their scent so they can sneak up on prey.
They use their sword-like rostrum (mouth part) to stab and pin down prey, injecting digestive fluids and sucking out their innards. Sometimes they raise their heads and run around with the impaled prey dangling in the air, it's funny.
Its the Ed Gein of the bug world :\
If you kill it, it drops the *Butcher Knife* which adsorbs health from enemies...