Them! is the first of the “big” creature features-its outsized ants would lead to gargantuan grasshoppers, extra-large leeches, massive mantises, colossal crabs, and that greatest of redundant enormities, the giant behemoth. The cause of this gigantism is radiation-spillage from some lax lab or military mishap in service of a Cold War gone haphazardly hot. Here, ants the size of picnic tables are found along a barren stretch of New Mexico desert-curiously close to Alamogordo. The entomologist assigned to the case (Edmund Gwenn) quickly determines that the strange killers with a sweet tooth are “a giant mutation . . . engendered by lingering radiation from the explosion of the first atomic bomb.” What has (human) nature wrought? The nest of mutated monsters is destroyed, but the ants have been antsy: the queen has moved on. Undaunted, the army will make sure she's only queen for a day. Or will they? Them! should be rated R for the adult use of radioactive material.