Exhibit 99.1Arch Capital Group Ltd. • December 8th, 2009 • Fire, marine & casualty insurance
The security holders are Warburg Pincus (Bermuda) Private Equity VIII, L.P., a Bermuda limited partnership ("WP VIII Bermuda"), Warburg Pincus (Bermuda) International Partners, L.P., a Bermuda limited partnership ("WPIP Bermuda"), Warburg Pincus Netherlands International Partners I, C.V., a Netherlands limited partnership ("WPIP Netherlands I") and Warburg Pincus (Bermuda) International Ltd., a company incorporated under the laws of Bermuda ("WPIP Bermuda Ltd.") that is the sole general partner of WPIP Bermuda. Warburg Pincus (Bermuda) Private Equity Ltd., a company incorporated under the laws of Bermuda ("WP VIII Bermuda Ltd.") is the sole general partner of WP VIII Bermuda. Warburg Pincus Partners, LLC, a New York limited liability company ("WPP LLC"), a direct subsidiary of Warburg Pincus & Co., a New York limited liability company ("WP"), is the sole general partner of WPIP Netherlands I. WP VIII Bermuda, WPIP Bermuda and WPIP Netherlands I are managed by Warburg Pincus LLC, a New
