The next stage, hibernating inside one of the eggs, is a parasite commonly refereed to as a face-hugger. Concealed by the egg for protection, the facehugger waits until the egg senses it is time to continue the life cycle. When a viable host is brought near a closed egg (either by curiosity, or being cocooned and held in place) it triggers the "contents" of the egg to come to life. The egg opens from the top to reveal the creature within it. At this point the cycle transfers from the egg to the next phase as the face-hugger awakens.
The facehugger is roughly one and a half meters in length (including its tail) with a long retractable tube-like organ that is thought to be its mouth. When a potential host is able to move around freely the facehugger will use its tail to launch itself out of the egg. If the facehugger fails to attach itself to the host it will use its six legs or fingers to move around in which it can move surprisingly fast. In such instances where a potential host is unable to move the facehugger will slowly crawl out of its egg and onto the host.
The face-hugger launches out at the organism and attaches itself by wrapping a long tail around its victim's neck and using long spider-like legs to firmly grip the organism's head. The legs become almost fused with the head of the soon-to-be host, making it extremely difficult to remove.
The facehugger can use various organisms as host. Being extremely versatile, it can adapt to various environmental conditions. The resin deployed by full-grown Xenomorphs to cocoon a host also serves as a guide to show the facehugger where its host is located. Once a facehugger attaches itself to a host it cannot be removed or else the host will go into a state of shock resulting in instantaneous death.
In order to ensure that the job can be completed with little outside interference, the face-hugger has concentrated acid for blood, serving as a possible self defense mechanism, and can strangle its host with its tail. This gives the facehugger a great advantage in which it can't be destroyed without destroying the host at the same time.
The facehugger, while attached, will alter its host's DNA so that the suppressant used to render the host immobile will not kill the host. The two sacs on the facehugger's body are how it breathes for a host while it is attached. A facehugger can stay alive while submerged in water and still breathe for the host because the two sacs act as filters, pulling in needed molecules and letting out by-product molecules. Due to the epidermis of the facehugger they can survive in extremely harsh conditions. During this process, however, the host is virtually helpless and completely dependent upon the facehugger.
The ability to alter a host's DNA plays a key role in embryo implantation, because the facehugger is able to alter the DNA of the host so it will begin to grow the embryo by itself. Once embryo implantation is complete, the weak facehugger will detach itself and crawl away until it dies. The acidic blood is neutralized upon death rendering the facehugger harmless. The host soon regains consciousness and has no recollection of its implantation. The life span of a facehugger after emerging from an egg is unknown.