Butterfield Bank dropped 2.5 percent (three cents) on The Bermuda Stock Exchange (BSX) yesterday.The bank traded 89,500 shares to close at $1.17.Argus Group Holdings Ltd also saw 37 shares change hands, but its share value held firm at $4.55.Overall the Index fell 14.22 points (1.31 percent) to 1,069.48 with 89,537 shares worth BD$104,890.75 and 1,080 shares worth US$8,586 transacted.The BSX Insurance Index also slipped 1.09 percent to 994.