Xenian Lifeforms

Headcrabs are the main 'Xenian Lifeform', normally called 'Headcrabs' By normal people, 'Parasitics' by Combine Soilders.

Headcrabs are fairly small creatures, but despite there size they can turn a person into a zombie.

INFECTION

Headcrabs infect a host by latching onto the victims head, they break through the victims skull and proceed to take over the hosts motor functions through some unknown bio-logical way. Then they will use the hosts arms to tear open there chest to feed. The hosts hands will become more elongated and skinless. Please note that the subject is conscious through the whole process. Now the poison headcrabs has the same process as the normal headcrab but the poison headcrab bloats the body and the reason is to store the neurotoxin inside the body.