EXEL Ltd., a Hamilton, Bermuda insurer, has acquired a 30% stake in Pareto Partners from its majority owner, Mellon Bank Corp., which also sold an additional 5% to Pareto's management. The transaction leaves Mellon with a 30% stake in Pareto and increases to 40% the interest held by the management's holding company, Palomar Management. Besides bringing in additional capital, EXEL will make it possible for Pareto to offer guaranteed products to its clients, as well as managing EXEL's own assets, said Lynne Minard director of marketing of Pareto. The transaction is expected to close before July. Terms were not disclosed.