This units are the workers of the Zerg Swarms.The drones are also morphed into buildings.By the triple production type of drones dependent to larva numbers the economics will be finer easily.The drones are fast units and heal theirselves very slowly however the recon efficiency is very low because they die easily.So the main recon unit is The Overlord.If your enemy is a Zerg like you you can send a drone at the early stages of the game and you can morph your drone into creep colony and after Spawning Pool mutation you can convert the creep colony into the sunkens.Yes now you have a sunken at the enemy base now watch the death of enemy drones.