Locusts are short-lived, ferocious, parasitic symbiotes. Powerful for their size, they are spawned from the millions of larvae that inhabit the swarm host's bloodstream. When the swarm host is threatened or engaged in combat, subtle chemical signals instruct the larvae to head for its incubator, where they are evolved into locusts.
Originally, locusts attacked any nearby enemy with volleys of acidic saliva. Since evolving pressurized air glands, locusts can attack aerial targets, and have developed the ability to fly themselves.
Swarm hosts enslaved by the Cerberus Program were enhanced with microfactories that equipped spawned locusts with remote controlled headgear.
The swarm host creates 2 locusts with a cooldown of 60 seconds. It is not autocast, but can be used whether the swarm host is burrowed or not.  Locusts are also able to fly, and must be ordered to land at a targeted area using "Swoop" in order to attack.
Upgrades and Abilities
Allows locusts spawned by swarm hosts to fly. Flying locusts can use Swoop to land and attack units.
Locust production inefficient. Will greatly benefit from redundancy removal. Sequences are complex, wasteful. Byproduct of wild, uncontrolled evolution. Simplification of sequences will allow swarm hosts to incubate full-grown locusts at rapid speeds.
Swarm host defense reliant on locust organism. Locust secrets solvent fluids, projectiles towards enemy. Can mutate glands, increase pressure. Will allow projectile to reach incredible height. Attack both ground and aerial targets.
Locusts are available to Abathur in Co-op Missions. They can be spawned via his swarm hosts, and can be upgraded at the infestation pit. In addition, Abathur unlocks an upgrade that gives him and his ally the random chance to spawn locusts from the bodies of dead enemies at Level 13.