The Spider was a mysterious vigilante adventurer in the 1930s and 1940s whose exploits were initially chronicled in pulp novels. He was really millionaire Richard Wentworth.
He also theorised that Wentworth had served as G-8 in the First World War, and that he had a split personality and accordingly was Kent Allard / The Shadow as well. Farmer retracted these ideas in Doc Savage: His Apocalyptic Life.
Dave McTaggart has suggested that Wentworth and his girlfriend Nita Van Sloan were the parents of Mack Bolan.