Larva

The larva is the base zerg unit from which all other units and, ultimately, buildings are created.

Overview
Larvae are the closest creatures to the original zerg insectoids. Although their size and toughness were greatly boosted by the xel'naga during their experiments, they still possess the two traits that originally intrigued the ancient masters: genetic versatility and psychic sensitivity. They often make a sucking sound from their tail section, akin to someone's boot stuck in mud.

Maggot-like, zerg larvae contain within them the genetic code for all other zerg breeds. When a new breed of zerg is needed, an individual larva will enter a pupal state and begin replicating the DNA of one specific zerg breed at an astounding rate. After a short gestation period, the new mature zerg minion hatches. Physically, they have a segmented, multilegged body, trailing a mucous-like substance behind them and a complex array of internal organs. Its small twin antennae probe the air around it.

A young hive will only have the genetic code for the most basic of zerg breeds, such as the drone, but as it grows and develops new structures, its library of genetic strains is expanded. With a command from the Overmind or a cerebrate, the larva will enter a pupal state and begin the metamorphosis into whichever breed is required by the hive. Within a larva's DNA are countless sequences, carrying billions of patterns and nearly infinite possible genetic combinations.

It is worth noting that larva has the dubious "honor" of being the first zerg strain ever encountered by the terrans of the Koprulu Sector. Around 2487 larvae were discovered on a number of fringe worlds. These worlds were depopulated by "cholera" and the specimens shipped to a Confederate science facility on Vyctor 5, only to be discovered by the Sons of Korhal nearly five years later.

StarCraft
Larvae are automatically produced by a hatchery, lair, or hive over time; up to a maximum of three at any one time per building. Players may only order larvae to evolve into other units. Larvae automatically "wander" near the building that spawned it. Larvae have very high armor and resilience despite having few hit points. They will automatically die if the creep underneath them dissipates. Canceling an evolution will also kill the larva.

StarCraft: Ghost
Concept art for larvae appears for StarCraft: Ghost. As seen, the larva appears larger and more adept at battle.

StarCraft II
Larvae are produced every 20 seconds from a hatchery.

If multiple hatcheries are selected, pressing the "S" hotkey will select all of the available larvae at all the selected hatcheries. The player must press a hotkey (or select a morph icon) once for each unit they wish to build.

Abilities

 * Mutate
 * A larva can produce a large variety of units: drone, overlord, zergling, roach, corruptor, mutalisk, hydralisk, infestor, and ultralisk.
 * However, there are some zerg units that are not produced by the morphing of larvae: queen, baneling, overseer brood lord, as well as spawned units such as broodlings and changelings.

Strategies
The ability to spawn additional larvae can indirectly help the zerg economy, as this enables them to produce a high number of drones (or a high number of combat units, or a mix of both).