Structures (Part 1)

Zerg Structures
Zerg structures can be found across the entire map and certain structures spawn their corresponding unit. (Roach warren spawns roaches, spire spawns mutalisks, ultralisk cavern spawns ultralisks) All structures, when destroyed, will spawn a random set of zerg units such as a bunch of roaches, zerglings or banelings. Certain structures may spawn more units that are much more lethal (Ultralisk caverns on the right side of the map has a chance to spawn 2-3 ultralisks on destruction)

Lairs and Hives spawns quite a lot of zerg units when destroyed, and should be approached with caution when destroying the primary structures.