Tarantula

From 1955, a giant furry spider menaces the countryside after a scientist tries to solve problems having to do with the world's overpopulation problems and instead makes animals grow huge-ish.

In other words, it's a kindler, gentler Food of the Gods.

Amazingly, this film does not appear to be available on DVD, at least not that I can find. Update: It's now back in print on the release, Classic Sci-Fi Ultimate Collection Vols. 1 & 2.

Buy Stuff - It Supports the Site!