Forum:Trap Eater Question

If your opponent activates a trap, can you chain Trap Eater to remove it? Or does it have to be a continuous trap on the field? All it says is "This card cannot be Special Summoned except by sending 1 face-up Trap Card your opponent controls to the Graveyard." Technically when your opponent activates a trap card, it's face-up on the field..so what's the ruling on that?