Swarm (canceled unit)

The swarm was a spawned zerg life form. They used to be created by swarm guardian attacks called swarm seeds.

Development
Swarms were also created when zerg structures were destroyed. The number of swarms produced depended on the importance of the structure. A lair would produce over 15 swarms, a baneling nest would produce fewer, and a spine crawler or extractor would produce none at all.

Swarms had a very short life span (measured in seconds).