In 14w06a, the mob AI was updated, but spiders and cave spiders lost the ability to see through walls. This is definitely a bug, because a quote from somebody on the Minecraft Forums proves it, and the quote was what Mojang originally said. Here it is: "The ability for spiders (and Cave Spiders) to see through walls was specifically added so they would not fall in the middle of climbing a wall.". And therefore, they are easier to combat.
Linked issues
is duplicated by 2
Comments 5
Duplicate or related to MC-64370?
How is this intended? Here's a quote from someone on the Minecraft Forums: "The ability for Spiders (and cave spiders) to see through walls was specifically added so they would not fall off in the middle of climbing a wall. "And therefore, they are easier to combat.
I thought it was strange too, but Searge is a Minecraft developer and he if says it's WAI, I guess they changed it.
@Tyler, the bug tracker doesn't automatically change anything. Any bug that's been changed to duplicate has been set that way by Mojang or the Mods. After being a Jira user for quite some time, I can honestly say most of the time they are duplicates. In fact, it's pretty rare that if two people have reported a bug similar, it's not a duplicate. You've got to understand that making something a duplicate is not a bad thing. It means more people can verify a bug exists and Mojang can track it easier.
It was a bug they could see through walls.