Sort of...it isn't called Legendary...it is called Freddy Mercury...no..wait...it is called Queen. It is hiding in a building waiting to jump your @ZZ, just like some of the members of Queen. Oooo Errrr, was that rude? I think I may have taken to many sinus meds.
Another one is in the desert north west of Nipton.
There's a unmarked tunnel there with a bunch of scorpions including the queen, as well as random prospector corpses.
That ant is also a queen, though not a fire ant one.