Spotters are zerg NPC units found in the map "Left 2 Die." Unlike overseers, they are capable of attacking ground and air units directly. They possess a contaminate ability similar to that of the overseer which can be used on structures. Unlike a regular overseer, they have a little round mouth and their regular, orange eyes are green.
The spotter is far more durable than the overseer, and moves at approximately the same rate. Its ability to incapacitate structures makes it very dangerous against lone bunkers or missile turrets.
Spotters appear as special infested on the Dead of Night mission of Co-op Missions. They are flying terrors that can deal bonus damage to structures, disable structures and give high ground vision for ranged attackers.