these 50s sci-fi monster movies are in a class by themselves. they have fun casts and a sense of let's try anything to scare the audience. and not all of them were about radiation. this movie has a pretty scary monster, who wouldn't be afraid of a giant spider? though as slow as it moves, if you can't outrun it you deserve to be eaten.
I remember being a bit spooked by the movie the first time I saw it, age 9 or 10. it's rightfully a minor classic. it was always fun, and still is, to some degree, to point out it's Clint Eastwood's debut.