quadtree's not to improve quality, but quantity see, each of the 200 spiders are checking their distance from every other spider every frame, right? that's 199 * 200 = 39800 distance checks each frame. with quadtree you could significantly reduce the amount of spiders checked to the few that are in the same grid-square as the spider (or include adjacent squares).
even splitting space into a consistent and regular grid should improve the speed.
see, each of the 200 spiders are checking their distance from every other spider every frame, right? that's 199 * 200 = 39800 distance checks each frame. with quadtree you could significantly reduce the amount of spiders checked to the few that are in the same grid-square as the spider (or include adjacent squares).
