Endermite

An Endermite is a mob that occasionally spawns when an Enderman teleports, or when the player teleports using an Ender Pearl.

Appearance
Endermites have a similar appearance to silverfish, except they are purple, emit the "portal" particles like other end-related items and mobs, and do not have the thin "frills" around them that silverfish have. Endermites will get a new model in a later snapshot.

Behavior
Endermites do not currently spawn naturally in any biome or dimension. Instead they occasionally appear in the place of an Enderman that teleports, or when the player throws an Ender Pearl. Each individual Enderman can only spawn a limited number of Endermites; every time it teleports, the chance of producing one is 15%, minus 1% for each Endermite it has already spawned. Ender Pearls have a 5% chance of spawning an Endermite when used.

Endermites are hostile towards the player. In Normal difficulty, Endermites do 2 damage per hit, as opposed to 1 damage for a silverfish. Endermen are hostile towards endermites and will easily kill them, allowing for mob sorting systems and resource friendly Enderman farms. Endermites are not harmed directly by water like Endermen are, but cannot swim and will drown if submerged for too long.

Due to some lingering Silverfish mechanics, if left alone, Endermites will try to "burrow" into a block, but, unlike silverfish, said blocks cannot be inhabited by Endermites. Similarly, Endermites make the same, albeit slightly deeper sounds as silverfish. Unlike other mobs, Endermites despawn within 2 minutes, unless they are named with a name tag. If they are named, they will last forever, unless killed.

Uses
If Endermites are named, they can be used to create Enderman farms, for Enderman will try to hunt and kill Endermites. Enderman can be lured to fall off a ledge while chasing an Endermite to create a simple farm. These Enderman farms that are extremly resource-friendly, compared to Enderman farm designs created prior to 14w11a, which usually require a lot of pistons, redstone and iron.

Trivia

 * Dinnerbone has stated he has an "Ultimate Plan" with Endermites that might include the dragon egg. However, he also mentioned he hasn't discussed this idea with the rest of the team yet.