I first saw this movie when I was a child. I can still remember refusing to go to bed that night until my mother checked underneath and proved to me that there weren't any ants lurking in the dark, just waiting to eat me alive. 
____________
Summary:
Them! is a 1954 American black-and-white science fiction film from Warner Bros. Pictures produced by David Weisbart, directed by Gordon Douglas, and starring James Whitmore, Edmund Gwenn, Joan Weldon, and James Arness. The film is based on an original story treatment by George Worthing Yates, which was then developed into a screenplay by Ted Sherdeman and Russell Hughes.
Them! is one of the first of the 1950s "nuclear monster" movies, and the first "big bug" feature. A nest of gigantic irradiated ants is discovered in the New Mexico desert; they quickly become a national threat when it is discovered a young queen ant and her consorts have escaped to establish a new nest. The national search that follows finally culminates in a battle with Them in the concrete spillways and sewers of Los Angeles.
____________
Summary:
Them! is a 1954 American black-and-white science fiction film from Warner Bros. Pictures produced by David Weisbart, directed by Gordon Douglas, and starring James Whitmore, Edmund Gwenn, Joan Weldon, and James Arness. The film is based on an original story treatment by George Worthing Yates, which was then developed into a screenplay by Ted Sherdeman and Russell Hughes.
Them! is one of the first of the 1950s "nuclear monster" movies, and the first "big bug" feature. A nest of gigantic irradiated ants is discovered in the New Mexico desert; they quickly become a national threat when it is discovered a young queen ant and her consorts have escaped to establish a new nest. The national search that follows finally culminates in a battle with Them in the concrete spillways and sewers of Los Angeles.