Is there anything I can do to attract spiders in Minecraft?

Solution 1:

There is no way to guarantee mob spawns of a particular type unless you happen to find a mob spawner. Your best bet is to simply set up a situation that allows a lot of enemies to spawn and then weed out the spiders.

There are a variety of traps that can be set up, from very simple to very complex. One of the easiest ways to get a lot of enemies to spawn, however, is to simply set up a tower in an open area (keeping you safe and able to see a large distance).

Spiders have three attributes that you can abuse to catch them:

• They are 2 blocks wide by 1 block high. All other enemies are taller than they are wide, so a 2x1 hole will allow spiders through while keeping you safe from other enemies. This can allow you to deal with them specifically if you want to build some sort of trap room.
• Spiders do not die from sunlight. This is why the tower tends to work well - even if a lot of monsters spawn nearby, you can wait for sunrise and then you will only have to watch out for creepers while you take down whatever spiders have spawned. As an added bonus, spiders will not be hostile during the day until you attack (or if they were already after you from nighttime).
• Spiders can climb walls (but a lip will stop them). A platform, at least two blocks high and well lit, can help you separate the spiders from other monsters, as only they will be able to climb up after you.

Solution 2:

You can abuse the Minecraft spawning physics to make a spider spawner. You see, all other hostile mobs (except maybe slimes, which only spawn at the bottom of the map anyway) require a 2 blocks high space to spawn in. However, spiders require a slightly different shape, a 3x3 square, but only one block high. So, if you want to spawn spiders, your best bet would be to make a two squares, one on top of the other, with a block of empty space between them. Due to the low height, only spiders will be able to spawn on the lower square, and because of the darkness (if you wall off the edges or make it large), they'll be the only ones to spawn there. You can then remove pieces of the top (when it's light out, so they'll be non-agressive), kill the spiders, and collect the string. (Obviously this would be impractical if you needed to reuse the device often, but since string is only really needed for bows/fishing rods, you don't need more than a handful of spiders)