The following section contains information from a previous version of StarCraft II which is no longer valid.
Early infestor model
used to be able to infestor infest protoss structures, which would spawn infested protoss, but that ability has been removed from the latest build of  StarCraft II. This model was later reworked into the  swarm host.
The infestor later lost its ability to
infest terran structures as well.
This ability was removed by October 2008.
 This ability was automatically researched.
 Dark Swarm worked similarly to the defiler's version, creating a smokescreen for units to hide under, protecting them from ranged attacks.   
 Dark Swarm protected units from a ghost's Snipe attack as well.
 A roach's attacks were unaffected by Dark Swarm.
The infestor used to have these abilities as well.
Disease does 100 damage to units in an area but does not actually kill units.
Beta Development Edit
The infestor targets a single unit or structure (even flying ones), draining it of 4 hit points per second and gaining half that back in energy. The ability is channeled and can be autocast.
infestor targets a single biological unit which deals 25% more damage and is immune to snare, stuns, and mind control for 30 seconds.
As Swarm Host Edit
Increases the lifespan of
locusts by 10 seconds (to 25 seconds). This upgrade was removed from HotS in the April 2015 update, as the locust's base lifespan was increased to 25 seconds.
This upgrade is not present in
. Legacy of the Void
In April 2015, during the development of
Legacy of the Void, the swarm host lost Enduring Locusts. This change applied to as well. Heart of the Swarm
Heart of the Swarm campaign, the swarm host had two unused upgrades. One increased the movement speed of locusts by 50%, the other increased their attack speed by 20%.
Fansite Q & A With Dustin Browder, p5. StarCraft Wire. Accessed on 2008-24-06
Pardo, Rob and Zetaras Xal'Kurat. 2008-06-29. WorldWide Invitational 2008: Pictures, Presentations, Videos (StarCraft II Panel: Evolving Design) SC2 Blog. Accessed 2008-06-30.
StarCraft II Beta Game Images. StarCraft Legacy. Accessed on 2010-06-22 ↑
4.0 4.1 4.2 Zetaras Xal'Kurat. 2008-10-17.
BlizzCon 2008: Changes to StarCraft 2. SC2 Blog. Accessed 2008-10-17.
↑ Medievaldragon. 2008-03-10,
StarCraft II-Zerg Unveiled. Blizzplanet. Accessed on 2008-03-10
↑ Zetaras Xal'Kurat. 2008-03-16.
StarCraft 2 Korean and Chinese Build Summary. SC2 Blog. Accessed 2008-03-18.
↑ Burnes, Andrew. 2008-03-10.
StarCraft 2 - Zerg Attack: New Screenshots, Unit Images & Unit Info! IGN.com Accessed 2008-03-10.
↑ Onyett, Charles. 2008-03-10.
StarCraft II Zerg Unit List: All the monsters in the game so far. IGN. Accessed 2008-03-11.
Karune. 2008-05-23. Dark Swarm performs the same way it does in the original StarCraft, negating ranged damage. Dark Swarm related. Battle.net StarCraft II General Discussion Forum. Accessed 2008-05-23.
Karune. 2008-05-23. Ranged damage going in or out of the area of effect will be negated. Dark Swarm related. Battle.net StarCraft II General Discussion Forum. Accessed 2008-05-23.
Units under Dark Swarm do not take damage from Snipe in the current build of the game. Karune. 2008-05-22. snipe and dark swarm? Battle.net StarCraft II General Discussion Forum. Accessed 2008-05-22.
Karune. 2008-05-23. Nevermind, Roaches will be able to shoot under Dark Swarm (current, being a bug). Dark Swarm related. Battle.net StarCraft II General Discussion Forum. Accessed 2008-05-23. ↑
13.0 13.1 13.2 13.3 StarCraft Legacy staff. 2009-04-04.
Zerg & Protoss Upgrades. SCLegacy. Accessed 2009-06-18
Karune. 2009-02-18. StarCraft II Q&A - Batch 49. Battle.net StarCraft II General Discussion Forum. Accessed 2009-02-18.
↑ AJ, LordofAscension, Joneagle X. 2008-10-11.
Live Coverage. Starcraft.org Accessed 2008-10-17. ↑
16.0 16.1 16.2
Already mentioned by a few, but M&Ms are very susceptible to any AoE type abilities/attacks. For example, they fall quickly to Banelings (if they get close enough, usually using burrow), Psi Storm, Colossi, Siege Tanks, and Disease (does 100 damage to units in an area but will not kill the unit - replacing fungal infestation). 2009-04-28. Terran strategy. Battle.net StarCraft II General Discussion Forum. Accessed 2009-04-28.
Karune. 2009-02-18. StarCraft II Q&A - Batch 49 (page 2). Battle.net StarCraft II General Discussion Forum. Accessed 2009-02-18.
↑ StarCraft Legacy staff. 2009-06-29.
June 22, 2009 StarCraft II Review . StarCraft Legacy. Accessed 2009-06-29. ↑
19.0 19.1 19.2 19.3 19.4 19.5 Blizzard Entertainment.
(Activision Blizzard) (in English). February 18, 2010 StarCraft II beta.
Infestor. StarCraft II Armory. Accessed 2009-09-03.
Zerg Infestation Pit. StarCraft II Armory. Accessed 2009-11-07.
↑ Blizzard Entertainment. 2015-04-07.
Heart of the Swarm Balance Update -- April 9, 2015. Blizzard Entertainment. Accessed 2015-05-11.
StarCraft II Legacy of the Void Beta Release Patch Notes. Blizzard Entertainment, accessed on 2015-04-03
↑ Blizzard Entertainment. 2015-04-07.
Heart of the Swarm Balance Update -- April 9, 2015. Blizzard Entertainment. Accessed 2015-05-11. ↑ Blizzard Entertainment.
(Activision Blizzard) (in English). March 12, 2013 StarCraft II: Heart of the Swarm Map Editor.