Them! (1954)

"A horror horde of crawl-and-crush giants clawing out of the earth from mile-deep catacombs!"

As a result of nuclear testing, gigantic, ferocious mutant ants appear in the American desert southwest, and a father-daughter team of entomologists join forces with the state police officer who first discovers their existence, an FBI agent and, eventually, the US Army to eradicate the menace, before it spreads across the continent — and the world.