Silly, good-natured and thoroughly unpretentious, this giant-spider movie has nothing more on its mind than providing the kind of brainless thrills once delivered by pictures like TARANTULA (1955), EARTH VS. THE SPIDER (1958) and THE GIANT SPIDER INVASION (1975). That's aiming low, to be sure, but the movie hits the mark neatly. While it occasionally drags a bit, the film captures the same tone knowing without being overtly jokey that made TREMORS (1990) so entertaining. Small town Prosperity, Ariz., is in a downward spiral: The once booming McCormick mines are played out, the Prosperity Mall has failed to prosper and ostrich farming just didn't take of...