Poison Headcrab

The Poison Headcrab (also commonly known as the black headcrab), is a Headcrab subspecies encountered in Half-Life 2 and its episodes. Like its relations, the Poison Headcrab is able to infest and mutate humans into Zombies.

It is unknown whether Poison Headcrabs are a natural subspecies never encountered on Xen or a result of Combine genetic manipulation of the Standard Headcrab for use in Headcrab Shells.

Physical Description
The Poison Headcrab can be identified by its dark colored skin (sometimes with a wet sheen) and thick hairs on the joints of its inward bending, spider-like legs. On the Poison Headcrab's legs are white bands that encircle the knee joints and the creature's dorsal markings are similar to those of a species of orb-weaving spider.

Behavior
At walking pace, the poison Headcrab is the slowest of the Headcrabs, but will run faster than a normal Headcrab if injured or under attack. Poison Headcrabs move slowly and cautiously when maneuvering but will leap with incredible speed and height with an angry squeal when it has a clear line of sight to a suitable host. This is possibly an ambush tactic, to poison the target so it can leap on the disorientated victim. Another way the poison headcrabs find players, is by whistling. Although this alerts the player, it almost sounds like a NPC is calling the player by whistling.

Venom
The Poison Headcrab delivers its extremely powerful neurotoxin via the four fangs on its "beak". In gameplay any contact with a Poison Headcrab will reduce the player's health to 1% immediately regardless of the current health amount. After a period of time, the HEV suit will provide an antidote that will restore the lost health, with 10% of it being lost from the headcrab's physical damage.

Contrary to popular belief, it IS possible for a poison headcrab to kill the player. Though in order for this to happen, the player must have 2-10 health remaining. However, if the player has exactly 1 health, they will not die to the headcrab's attack, even if they're not under the effect of the poison. This means that, for example, if a player has 41 health, they will not die to the headcrab if bitten enough times, as they will eventually be left with 1 health. But if the player had, say, 36 health, they will die if bitten enough times.

Tactics
The Poison Headcrab is best engaged from a distance, where either the shotgun or the pistol prove effective. In close quarters, a well-placed strike from the crowbar can kill them instantly.

Trivia

 * According to Half-Life 2: Raising The Bar, the development team noticed that upon hearing the Poison Headcrab's sound playtesters would frantically start looking around for the Poison Headcrab so they could destroy it, regardless of any other present dangers.
 * The Poison Headcrab's second scream,, appears to be a sped-up version of the Fast Zombie first scream ( , the "Howie Scream").
 * If severely hurt, the Poison Headcrab will attempt to hide or run away from the player, in hopes that it will not be killed. It is also interesting to note that on rare occasions, the Poison Headcrab will ignore the player and try to seek refuge in a corner or secluded area.
 * A player can also be killed by a Poison Headcrab by standing on it and shooting it with the Gravity Gun.
 * If a Poison Headcrab is eaten by a Barnacle, the Barnacle will die after swallowing it.
 * An interesting note is that when a Poison Headcrab's maw is looked at closely, a skull-and-crossbones can be seen in the flesh.
 * Poison Headcrabs are extremely dangerous to NPC characters, as they lack Gordon's HEV suit and thus have no access to the antidote for the neurotoxin. As a result, a hit from a poison headcrab will permanently reduce an NPC's health to 2, allowing them to be instantly killed the next time they receive damage. Alyx Vance, Barney Calhoun, and Father Gregori have regenerating health, and thus the poison headcrab is less of a threat to them provided they are not under heavy attack from other enemies.

List of appearances

 * Half-Life 2
 * Half-Life 2: Raising the Bar
 * Half-Life 2: Lost Coast
 * Half-Life 2: Episode One
 * Half-Life 2: Episode Two