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The queen lays soft, leathery eggs, inside which a parasitic larval form called a "facehugger" develops. The laid egg can remain in diapause for a long time under unfavorable conditions. The egg hatches, releasing the facehugger, when it "detects" the presence of a viable potential host nearby [11]. The facehugger is a mobile arachnid-like creature with eight long, multi-jointed limbs and a long, muscular tail, which is used for movement, capturing the future host, and holding the parasite's body to it. The facehugger's sole purpose is to find a potential host, capture it, and implant "black goo" (as confirmed in the official book "Aliens: Cold Forge"), from which the next creature grows. When the facehugger finds a future host, it leaps onto the victim's face and secures its position using its limbs, also wrapping its tail around the victim's neck. After this, it induces the host into a coma and implants the "black goo." Some time after the substance is implanted, the facehugger leaves the "host" and soon dies, and the host's vital processes return to normal—it regains consciousness and begins to feel intense hunger, as the developing organism requires a large amount of nutrients.

Due to horizontal gene transfer during maturation, the xenomorph inherits a number of key physiological characteristics from its host, which help it adapt to the conditions of the host's usual environment (for example, a special form—the runner—develops in four-legged hosts). Cases of infection of humans, terrestrial animals[12], Predators[13], and Space Cowboys[11] by xenomorphs have been shown. The development of a typical embryo lasts from several hours to a day and a half.

Chestbreaker
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A fully developed embryo is called a "chestburster" because it emerges from the host's body (in humans and other vertebrates).