"The Black Scorpion" released 1957

One of a number of big bug movies, The Black Scorpion, was released October 11, 1957.  A series of volcanic eruptions release giant scorpions from underground caverns and they threaten to demolish Mexico City.

The movie appears to have received some good reviews for its stop-motion animation effects.  It was featured in an episode of Mystery Science Theater 3000.

"The Deadly Mantis" released 1957

The Deadly Mantis, released May 26, 1957, was a black and white science fiction movie that featured, well...a gigantic praying mantis.  It's one of a subgenre of big bug movies such as Them!, The Black Scorpion, The Beginning of the End, The Tarantula, and of course, Mothra!

It starred Craig Stevens, William Hopper and Alix Talton.

It garnered most negative reviews, claiming it was a rip-off of Them!, but sci-fi fanatics still enjoy it for its cheesy effects and good ol' plain fun!