Paul S. Amos, who co-founded Aflac with his brothers and helped build it into the largest seller of supplemental insurance, died July 2 in Columbus, Ga. He was 88.

A spokesman for Columbus-based Aflac confirmed the death but did not disclose the cause. Mr. Amos was chairman emeritus, and still visited the insurer daily after retiring in 2001.

Along with his brothers William and John, Paul Amos started American Family Life Insurance Co. in 1955. The company soon introduced a policy designed to cover expenses for people with cancer, marketing it to groups of employees at their firms. In 1964, the name was changed to American Family Life Assurance Co. It was shortened to Aflac in 1989.

Aflac, now led by Paul’s son, chief executive Daniel P. Amos, 62, entered Japan in the 1970s. The country accounts for about three-quarters of the firm’s business. Aflac has more than 50 million policyholders worldwide and $121 billion in assets.

Paul Shelby Amos was born in Enterprise, Ala., on April 24, 1926, and was the youngest of three boys. His father, the town postmaster, sold insurance on weekends and served one term in the state legislature.

At Aflac — where he was known as Mr. Paul — Mr. Amos managed sales in Alabama and West Florida, and later oversaw marketing, according to the company’s statement. He later took on the titles of president and chairman.

The insurer is known for its use of a talking white duck in advertisements. The bird’s first commercial aired in the United States in 2000 and in Japan in 2003. The insurer changed its logo to include the duck two years later.

Paul Amos was the last survivor among the three co-founders, the company said. In addition to his son, survivors include his wife, Jean Roberts Amos; Paul S. Amos II, his grandson and Aflac’s president; a granddaughter; and four great-grandchildren.

— Bloomberg News