The Spider was one of the most prolific of the pulps, running for 118 issues between October 1933 and December 1943, consisting of pulp novels centered on the single dark-hero figure of Richard Wentworth. It seems appropriate to cover here, for as the Galactic Central Index notes, [m]ost of the novels have a macabre tone that matches that of the horror pulps; many have actual SF/fantasy elements.” A well-suited tonal match for Erotic Mad Science! I don’t intend to cover this pulp comprehensively, but I’ll pick some of my favorite covers for this series. (Completists can refer to the Galactic Central index page to pick their own favorites.) Here is the cover of the first issue, from October 1933.

This is the image from the Galactic Central index page. (Internet searches found possible larger versions, but their links all seem to have died, sadly.) Some pages suggest that the illustrator might be Walter M. Baumhofer (1904-1987).