The above animal measures from pedipalps (pincers, claws) to the start of the tail about 6 cm. It is the largest vinegaroon I have seen in Mexico so far.
The antennae are actually the specialized first pair of legs, and are used to feel around, or as Esme remarked, like the stick of a blind man. I have seen whip scorpions use their tail in a similar manner.
Note that the vinegaroon can spray acid which might cause an allergic reaction Don't handle whip scorpions unless you're sure what you are doing and know that you are not allergic to the acid mist it can spray in defense.