Gordon kept the grasshoppers in a box for only a few days, but during that time the grasshoppers devoured one another and only 12 were left when Gordon finally got around to shooting them. Gordon also considered building miniatures for the grasshoppers to climb on, but this, too, was deemed too expensive. Instead, Gordon used still photographs of the Wrigley Building and other noted Chicago landmarks and simply filmed the grasshoppers moving about on top of the photograph. When the monsters are supposed to be wounded or killed by gunfire, Gordon merely tipped the photograph and the grasshoppers slid down it. According to one film historian, "the effect looks (almost) real" until one of the grasshoppers steps off the "building" into what is supposed to be thin air.