When going through my 14w18b Hardcore world, I realized none of the Endermites actually worked. They stayed in one place, spinning rapidly, and they weren't stuck in a block, as I cleared the blocks around them, and they persisted in their spinning. They fell normally when I broke the blocks under them, and I can't hit them, nor can they attack me, and Endermen had no reaction to them. I found only one working Endermite of the three, and nothing seemed wrong with how it moved, attacked, or anything else. The non-working mites were in a Plains biome, and the working in an Extreme Hills biome, if that matters.