The FBI's capture of a prominent figure in what it calls the nation's worst domestic terrorist threat may do little to slow the radical environmental movement known as the Earth Liberation Front, federal authorities acknowledge. The suspect, Tre Arrow, also known as Michael Scarpitti and numerous other pseudonyms, is a charismatic figure who has run for political office before running from the law after being accused as the ringleader in a pair of environmentally motivated arson attacks. "It's a very big capture for us," said Beth Anne Steele, spokeswoman for the Portland, Ore., office of the FBI. "[The suspect has]...