Shares of Argus Group Holdings Ltd plunged 13 per cent in Bermuda Stock Exchange trading.The insurer fell 31 cents to close on $2.08 as 70,000 shares changed hands. Argus was the only stock to trade as The Royal Gazette/BSX Index fell 6.2 points, or 0.41 per cent, to close on 1,502.85.Butterfield Bank’s US-listed shares fell 46 cents, or 2.4 per cent, to close at $18.71 on the New York Stock Exchange. The bank last traded on the BSX at $18.10.The BSX Insurance Index closed higher by 89.79 points, or 6.93 per cent, to close on 1,386.27.