The spore colony is a zerg means of anti-aerial defense. Able to fling seeker spores (a corrosive variation of creep) high into the atmosphere, spore colonies can quickly ravage any incoming enemy air force. In addition to its anti-air capabilities, the spore colony also serves as a stationary detector against any enemy cloaked or burrowed units thanks to a special sensory organ similar to that possessed by overlords.
Anti-air defense structure
Combined with the sunken colony (required for defense against ground units), the spore colony can be a very strong deterrent against any aerial invasion. However, because it cannot move, it is vulnerable to long-range attacks (such as those of guardians).
This article or section contains information about StarCraft: Ghost, which has been declared non-canon. Elements may be taken as 'flavor lore' however.
The following section contains information from a previous version of StarCraft II which is no longer valid.
The spore colony could move on crab-like legs outside of the boundaries of creep, but like other zerg structures would slowly degenerate and eventually die if it remained outside of the boundaries for too long. Spore colonies could not be planted outside of the creep.