Line 312, Book 7 of Vergil's Aeneid.
Variously translated as "If I cannot bend the Powers Above, I will move the Infernal Regions." and "If I can not influence the gods, I shall move all hell", or, more dramatically, "If I cannot move heaven, I will stir up the underworld.".
As well as being a type of butterfly (Historis acheronta, or the Tailed Cecropian
) from the United States and Mexico, Acheronta is the accusative of Acheron - one of five rivers in the Greek underworld, mentioned first in Homer's Odyssey, along with to the more famous river Styx.
This is the motto of Sigmund Freud's significant work The Interpretation Of Dreams. The controversial Freudian psychologist Bruno Bettelheim claimed that it was a summary of Freud's theory that those who have no control over the outside world turn inward to the underworld of their own minds.
I suppose you could use this as a comeback to that other excerpt from the Aeneid.
Tenses In Latin - http://ist-socrates.berkeley.edu:7004/lessons/36-preview.html
Recollections and Reflections - Bruno Bettelheim
With thanks to tdent, Txikwa and Halspal.