Shares of Argus Group Holdings tumbled 27 per cent in Bermuda Stock Exchange trading.The insurer shed 85 cents to close at a 52-week low of $2.30 as 20,000 of its shares changed hands.Argus was the only stock to trade and The Royal Gazette/BSX Index fell 16.99 points, or 1.08 per cent, to close on 1,555.57.Butterfield Bank’s US-listed shares fell 77 cents, or 4.31 per cent, to close on $17.09 on the New York Stock Exchange. The bank last traded on the BSX at $19.The BSX Insurance Index gained 2.71 points, or 0.24 per cent, to close on 1,124.97.