NEW YORK (AP) ¿ Standard & Poor's said Tuesday it will add Employers Holdings Inc. to its S&P SmallCap 600 index. Employers Holdings, which sells workers' compensation insurance and services to small business, will replace Catapult Communications, which makes digital communications test systems, since Catapult is being acquired by network hardware maker Ixia. Meanwhile, S&P SmallCap 600 constituent WMS Industries Inc., which makes gaming products, will replace The Colonial BancGroup Inc. in the S&P MidCap 400. Colonial BancGroup market capitalization does not meet minimum requirements for the index. Badger Meter Inc., which makes products incorporating liquid flow measurement and control technologies, will replace WMS Industries in the S&P SmallCap 600.