Larva

The larva was the base unit of the zerg, the form from which all other strains and, ultimately, the Swarm's structures were created. Closest of all zerg to the original insectoids that the xel'naga had first uplifted, the larva retained the two traits that had drawn the attention of those ancient masters: an extraordinary genetic versatility and a sensitivity to psionic command. (StarCraft)

Physiology#

The larva was a small, maggot-like creature that often made a wet sucking sound from its tail section, likened to a boot pulled from mud. It had a segmented, many-legged body that trailed a mucous-like substance behind it, twin antennae that probed the air, and a complex array of internal organs. (StarCraft; StarCraft: Uprising)

A larva used its tendrils both to absorb nutrients from creep and to move, and it depended utterly on creep to live, surviving only hours to days if cut off from it. It also carried a number of extra organs that kept it compatible with the Swarm's vast genetic library. (StarCraft Field Manual; In the Blood)

Reproduction and metamorphosis#

Within a larva's DNA lay countless sequences carrying billions of patterns and nearly infinite genetic combinations, holding the complete code for every other zerg breed. When the Swarm needed a new strain, an individual larva entered a pupal state and began replicating the DNA of one specific breed at an astounding rate, hatching as a mature zerg after a short gestation. A young hive held only the code for the most basic breeds, such as the drone, but as it grew and developed new structures its library of strains expanded. (StarCraft; StarCraft: Uprising)

On a command from the Overmind or a cerebrate, the larva would begin its metamorphosis into whatever breed the hive required, sealing itself in an egg-like cocoon for a brief pupation whose length depended on the breed being grown. This metamorphic power was the source of the Swarm's terrible resilience: a single surviving larva could mutate into a drone, which could mutate into a hatchery, which could give birth to an entire reborn colony. For that reason the Terran Dominion stressed that its marines be obsessively thorough in zerg eradication. (StarCraft; StarCraft: Brood War; In the Blood; StarCraft Field Manual)

First contact#

Larvae were the first zerg strain ever encountered by the terrans of the Koprulu Sector. Around 2487, specimens were discovered on a number of fringe worlds that had been depopulated by what was reported as "cholera." The larvae were shipped to a Confederate science facility on Vyctor 5, where they remained until they were discovered by the Sons of Korhal nearly five years later. By the Battle of Adena, larvae could also be generated, or at least regurgitated, by the infestors of the Niadra Brood. (StarCraft: Uprising; StarCraft II: Shadow Wars)