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This article is about the species. For the most common subspecies, see Standard Headcrab.
"Have you ever seen such a magnificent species? These 'crab' creatures can completely control their host's nervous system. Can you imagine what the next stage of mutation looks like?"
Black Mesa scientist[src]

Headcrabs, derisively called "headhumpers" by Barney Calhoun and known as "parasitics" and "biotics" by the Combine, are omnivorous, parasitic creatures. They are widely considered one of the most iconic creatures of the Half-Life series.


Headcrab underbelly

The Standard Headcrab's underbelly.

Headcrabs are small creatures, roughly the size of a pumpkin. They are covered in smooth skin, which varies in color between subspecies, and crawl on four short legs. These provide enough jumping power to leap up to 3 meters (10 feet) in any direction.

Their underbelly is almost completely covered by a large, jawless mouth, with a hidden 'beak' used for feeding and for latching onto the skulls of victims (see below). As seen on Xen, Headcrabs appear to typically be born out of a Gonarch; therefore, some Headcrabs may mature into Gonarchs as part of their natural life cycle.

The Headcrab's natural predator appears to be the Bullsquid. Several scenes in Half-Life feature Bullsquids using their ranged attack to kill Headcrabs, which make no attempt to defend themselves. The Bullsquid then comes crawling over to feed on them.

Headcrabs were studied at Black Mesa, notably in the Advanced Biological Research Lab and the Gamma Labs.

Headcrabs are one of the three enemies in the game that can be killed with the Gravity Gun, after a few hits. The other being the Antlion Soldier/Worker.

During the Combine occupation of Earth, Headcrabs appear to have no external sensory organs, including eyes or ears, while the Standard Headcrab had 3 eyes on each side of their bodies 20 years prior. The Standard Headcrab can also be seen burrowing in and out of the ground, but not the other species.

There are several Headcrab subspecies;

  • The Standard Headcrab - the first Headcrab introduced in Half-Life, seen in their infant form near the end of the game. They turn their hosts into a Standard Zombie, and in some cases a Gonome.
  • The Fast Headcrab - introduced in Half-Life 2, and much faster than Standard Headcrabs. They turn their host into a Fast Zombie.
  • The Poison Headcrab - a toxic Headcrab, causing more damage to the host. Also introduced in Half-Life 2, they will turn their host into a Poison Zombie.
Lamarr and Kleiner

Lamarr and Kleiner.

Headcrabs can be domesticated, as seen with Lamarr, Isaac Kleiner's pet Headcrab. Lamarr has been de-beaked; removing the beak of a Headcrab renders it unable to break into a host's head, rendering them harmless and apparently somehow suppresses their parasitic instincts.

It appears that both Standard and Fast Headcrabs are edible, at least to a Vortigaunt. The Standard Headcrab can be seen being prepared by Vortigaunts in Black Mesa East while fast headcrabs can be seen being roasted by the All-Knowing Vortigaunt. The Poison Headcrabs, however, are not edible; if a Barnacle consumes one of them, it dies after swallowing the Headcrab's poison.


Main article: Zombie

Headcrabs are a parasitic species. Upon sighting a humanoid host, a Headcrab will leap for the victim's face and affix themselves to the head, whereupon they will use their beak to break into the victim's skull. The Headcrab then proceeds to take over their host's motor functions through an unknown biological process. The host will then undergo physical changes, presumably induced through chemical means; although the mutations vary between Headcrab subspecies, common changes include the elongation of hands and fingers, reduction or removal of skin and muscle tissue across much of the body, and the exposure of the organs inside the chest cavity. Headcrabs keep their host alive throughout the entire process, unable to remove the headcrab. As seen in Station 6 in Half-Life 2, they apparently take anywhere from several seconds to several minutes for a Headcrab to convert their hosts into Zombies.

The host appears to stay in some state of consciousness once the Headcrab has taken control. Standard Zombies retain a certain ability to talk, always heard as violent cries for help. "Zombines" seem to be able to speak with their vocoders. Each Headcrab subspecies affects their host in their own unique way, producing a Zombie extremely distinct from the other types, in both appearance and behavior.

Combine application

Main article: Headcrab Shell
Headcrab shell station 6

Standard Headcrabs emerging from a deployed Headcrab Shell.

In Half-Life 2, the Combine are seen utilizing Headcrabs as a form of biological weaponry against the Resistance. "Headcrab Shells," as they are known, are large mortar shells containing a payload of Headcrabs, which are released on impact, free to infect or terrorize anyone nearby. If used in large numbers, these shells are highly effective in neutralizing a large Resistance base. The effects of large-scale Headcrab shelling are seen during Gordon's visit to the devastated town of Ravenholm, where most inhabitants have been turned into Zombies.

In Episode One, it seems that the Combine have begun to lose control over their bio-weapon; Headcrabs begin infecting Overwatch Soldiers, showing that the large-scale effects of shelling have caused even Combine-controlled areas to be affected.

Behind the scenes

Combine BM Pod

The Combine Big Momma Pod.

  • Originally, a device holding a Gonarch's sack, nicknamed the "Combine Big Momma Pod" (a reference to the Gonarch's nickname), was to be used by the Combine for obtaining large numbers of Headcrabs for use in Headcrab Shells,[2] and to be encountered in the Ravenholm mine.[3] Since the device does not appear in the final games, it is unknown so far how the Combine breed their Headcrabs.
  • While the Headcrabs found in Half-Life and its expansions are able to swim and survive in water but not in areas contaminated by toxic waste and radioactivity, this is reversed in Half-Life 2 and its Episodes ; where Headcrabs can be found surviving in toxic areas, and drowning when entering water. The Headcrab's new resilience towards toxic and radioactive materials even appears to be passed on to the hosts they infest, as Zombies are frequently found in conditions that would otherwise be hazardous to their hosts.
  • The Headcrabs in Half-Life 2 cannot attack the player if he is inside a vehicle. They will only rush at the vehicle and attempt to push it, but they end up being crushed by the vehicle instead. However, this can be advantageous to Poison Headcrabs since their attack can be very dangerous.


Half-Life and its expansions

Half-Life 2 and its Episodes

Official merchandise

List of appearances

External links


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