In one of the great openings in movies, a girl (Sandy Descher) staggers through the New Mexico desert, dazed and mute. Then she erupts into hysterics, screaming, “Them! Them! THEM!” The them are giant ants, magnified to 18-wheeler size by the atomic bomb tests in nearby Alamagordo. The antosaurs somehow set up their formicary in the Los Angeles sewers, where they’re faced down by the usual bunch of cops and scientists (including the Thing himself, James Arness). And it’s no picnic. This superior drama — not a B but a B+ — boasts brisk, no-nonsense direction by Gordon Douglas, working from a story by sci-fi movie ace George Worthing Yates (It Came from Beneath the Sea, Conquest of Space, Earth vs. the Flying Saucers, Earth vs. the Spider…).