Question: What was the purpose of the bag on the hood ornament of the police car in the beginning of the movie?
Answer: The bag is "spare" radiator water for when you're in the desert.
Question: Did anyone notice, or can explain how both James Whitmore, a state trooper, and James Arness, an FBI agent suddenly become outfitted in Army or National Guard uniforms, fully qualified to fire bazookas, etc and more or less in charge when the action moves to the pursuit in the LA sewer? seems like there would have been jurisdictional issues there (at least for James Whitmore).
Answer: Like the General said, the less people that know about the ants the better. They were a special task force assigned with the equipment and deputized to use any and all measures to stop the ants. Since the movies was set in the 1950's, James Arness and James Whitmores were most likely veterans of WW II and Korea.
Answer: You fill the canvas bag with water, put it somewhere where the air can blow through, and the evaporation of the water seeping through the canvas creates cool water inside.
stiiggy