Antlion Grubs are the larval stage of the Antlion species in Half-Life. They closely resemble the larvae of many Earth-based insects, with soft, translucent bodies and under-developed limbs. They also have small mouths that open and close slowly. They emit a high chirping call and bioluminescence similar to that of a firefly. They are found only deep inside Antlion colonies, and can be seen hanging on any available surfaces, often in groups of two or more. They are extremely fragile and can be killed by merely bumping into them. In the hive, human remains are sometimes found scattered on the ground near Grubs, suggesting that they are carnivorous and are presumably provided with food by mature Antlions. Grubs also exude a filmy thread, similar to that of a silkworm but on a much larger scale.
When killed, Antlion Grubs will release glowing yellow pellets which can heal the player. How much health these pellets restore varies depending on the pellet size and how much health the player still has. The Vortigaunt have stated that they once harvested grub pellets as some sort of ancestral practice.