Yeah, this was actually a real movie. I saw it. Undoubtedly, the cause of the mutant spider was radiation....
You know how they killed it? They got the 50-Foot Woman to step on it.
FYI: John Agar was one of Shirley Temple's husbands.
Thanks to Eric Fitch for the sign graphic.
"Some things man was not meant to experiment with." -- Unknown, always uttered by someone in a 1950s horror movie