Butterfield Bank closed down 5.5 percent on the Bermuda Stock Exchange (BSX) yesterday.A total of 100,000 of the Bank’s shares changed hands, closing at $1.37, down 8 cents.It was the day’s only trade on the BSX.The BSX overall closed down 3.15 percent, or 38.27, at 1,178.17.The BSX Insurance Index closed down 16, or 1.83 percent, to end the day at 859.00.