The flamethrowers used in the movie were standard World War II weapons and were loaned by the U.S. Army. The actors handling the weapons were World War II combat veterans, who had used them in battle.
In 1998 Joan Weldon revealed that the temperature reached 110 degrees Fahrenheit (43 degrees Celsius) during filming, and she and Edmund Gwenn were wearing wool clothing. Gwenn struggled with advanced arthritis. Although unnoticeable to audiences, he was in pain and was helped off-set by his valet.
The film was originally to have been filmed in color. Two days before shooting began a nervous studio cut the budget, and the film had to be made in black and white. However, in the opening credits, the title is shown in bright red against a black-and-white background.
Walt Disney screened the movie because he was interested in casting James Arness as Davy Crockett. However, he was so impressed by Fess Parker as the "Crazy Texan Pilot", that he chose him for the part.
The viewer never sees more than three giant ants at any one time. That is all that were constructed.