Minecraft wiki entry for Spider, associated text: Spiders become hostile toward players and iron golems as long as the light level immediately around them is 11 or less; otherwise, they do not attack unless attacked. Hostile spiders see up to 16 blocks, continuing to chase even when exposed to well-lit locations. If a spider sustains damage from a source other than a direct attack, such as falling, its hostility resets to a neutral state.