Richard Fiske (Jackson)
(1915-1944) Young supporting actor Richard Fiske was born Thomas Richard Potts in Shelton, Washington, on November 20, 1915. As a contract player at Columbia Pictures from 1938 to 1942 he appeared in over 80 films (many uncredited) in his four short years there. His first credited role was, in fact, playing Wentworth's faithful chauffeur Jackson in The Spider's Web (1938). He upgraded to serial HERO the following year as one of the Flying G-Men (1939). He also played opposite the Three Stooges, comedy star Andy Clyde, and William "Wild Bill" Elliot (in a total of eight westerns). Sadly, Richard Fiske was killed in action in LeCroix, France, during World War II.

Forbes Murray (Commissioner Kirk)
Forbes Murray started his screen career in 1936, already a middle-aged man with the quiet dignity of a cut-rate Claude Rains. He spent his thirty year career playing mostly judges, doctors, army officers, and bank presidents (he even gave Laurel & Hardy college loans in A Chump at Oxford). Looking down the list at IMDB, Murray spent the majority of his 250 film appearances as an uncredited extra, usually in some ritzy setting like an auction, casino, cruise ship, or theater. His most memorable work however was in serials like The Spider's Web (1938), Perils of Nyoka (1942), and Radar Patrol vs. Spy King (1950). He reteamed with Warren Hull in Mandrake the Magician (1939), and in two other features. Murray crossed paths with Richard Fiske in Flying G-Men (1939) and five other films. He was so prolific in B films, as was Kenneth Duncan, that they overlap in fourteen projects!

Donald Douglas (Jenkins)
(1905-1945) Scottish-born actor Donald Douglas came to Hollywood in 1934 to appear in the film adaptation of Sidney Kingsley's Men in White (1934). He worked steadily through 1945, generally playing secondary roles as lawyers, military or police officers, and FBI agents. In 1940 he got the opportunity to headline his own serial (in a rare leading role) playing Deadwood Dick -- the first western serial that James W. Horne directed solo. In 1944 he notably faced off against Dick Powell's Philip Marlowe in Murder My Sweet as Police Lieutenant Randall. Douglas only really got to stretch himself on radio, where he voiced all the parts in Mutual Network's mystery anthology Black Castle (1943). Tragically, Don Douglas died before his time, of complications resulting from an emergency appendectomy at the age of 40.

Other Players
In "The Spider Serials, A Critical History" (The Spider, Book One: Blood Dance, Eclipse, 1990) George E. Turner and Michael H. Price give the following rundown of other notable cast members:

The expendables include such notable actors as Nestor Paiva (popular villain in the long-running play, The Drunkard), Ernie Adams, Harry Semels, and Bert Young. Dominant among the heavies is the excellent Marc Lawrence, whose portrayals of gangsters for more than half a century are real cinematic art. Also arrayed on one side of the law or the other are ex-matinee idols (Edward Earle, Edward Hearn), ex-comedy stars (Harry Myers, Kit Guard, Eddie Featherston), ex-Western stars (Lane Chandler, Bill Patton, Eddie Cobb, Tom London), and ex-sports stars (Oscar "Dutch" Hendrian, Frank Hagney). There are even roles for Joan Blondell's kid sister, Gloria, and the lovely Ann Doran.

For a full list of cast and crew go here.