The closest creatures to the original Zerg insectoids are the Zerg Larvae. 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.

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 hatches.

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, the Larva will enter a pupal state and begin the metamorphosis into whichever breed is required by the hive.

Larvae are produced at the Hatchery, Lair and Hive. They spawn one at a time up to a maximum of 3 per Hatchery/Lair/Hive. They require the Creep to survive and should the Creep ever dissipate from beneath them, the Larvae die shortly after. Unlike the mature Zerg breeds, Larvae do not require Overlord control and therefore can only be commanded to mutate by a Cerebrate.

To easily select all the Larvae from a particular Hatchery/Lair/Hive, select the Hatchery/Lair/Hive and hit the S key and all available Larvae will be highlighted. An alternate method can be used by holding down the Ctrl key while left clicking on one of the Larva -- this will select all the available Larvae on screen. Be sure to use one of these techiniques when you've progressed far enough to begin producing the mature Zerg breeds, as it will greatly increase the speed that you'll be able to morph Larva.