Xeno cycle

Graphic showing the basic stages of the Xenomorph life cycle.

The life cycle of the species Xenomorph XX121 is a complex process involving several distinct stages and the use of a living host organism as a vessel inside which the infant Xenomorph gestates. The cycle, and in particular the use of hosts that invariably perish when the infant Chestburster forces its way through their ribcage, is often considered the species' signature aspect and is the characteristic for which they are most well known.

Note that this article is not a comprehensive list of all known Xenomorph castes, but merely lists the key stages in the creature's life cycle.


Xenomorph life cycle

The Xenomorph life cycle is comparable in many ways to certain parasitoidal insects found on Earth, such as the wasps of the Chalcidoidea and Ichneumonoidea families, which lay their eggs on live prey that are then consumed by the hatching larvae. However, the cycle is at the same time unique, particularly with regards to the manner in which the infant Chestburster stage develops — instead of simply being implanted as a fetus and growing within the host, the Chestburster is actually more akin to a cancerous growth that assembles itself using the host's own cells and biological material as building blocks.[1] The corresponding transfer of genetic material, referred to as the DNA reflex,[2] causes the physical attributes of the adult creature to vary.

The Xenomorph life cycle consists of five primary stages — the Ovomorph, the Facehugger, the Chestburster, the adult and finally the Queen. The adult stage can be further subdivided into a number of forms or castes, each with differing physical characteristics based on age, function or the genetic makeup of the host creature.

Early Life Cycle


Main article: Ovomorph (Egg)

The Ovomorph or Egg is typically considered to be the first stage of the Xenomorph's life cycle. Eggs are laid by a Queen and are large, ellipsoidal leathery objects between two to three feet high with a four-lobed opening at the top. As a potential host approaches, the Egg's lobes unfurl like flower petals, and the parasitic Facehugger within extracts itself from within and attaches itself to the potential host.


Main article: Facehugger
Alien-The Facehugger

A Facehugger attached to Thomas Kane.

A Facehugger is the second stage in the creature's life cycle. As its name suggests, it attaches to a victim's face, and its sole purpose is to impregnate them orally with the beginnings of a Xenomorph embryo. Upon making contact with a potential host, the Facehugger quickly renders them unconscious through the use of a cyanose-based paralytic chemical.[3] The Facehugger then inserts a proboscis down the host's throat, supplying it with suitable atmosphere[4] whilst simultaneously implanting the next stage of the creature's life cycle. Attempts to remove Facehuggers generally prove fatal,[5] as the parasitoid will respond by tightening its grip and suffocating the host, while the Facehugger's acidic blood prevents it from being safely cut away.[4] Once the Xenomorph embryo is safely in place, the Facehugger detaches, crawls away and dies.


Main article: Chestburster
Alien-The Chestburster

A Chestburster immediately after "birth".

Arguably the most biologically intriguing stage of the Xenomorph's life cycle, the Chestburster is not implanted into the host as an embryo but is in fact akin to a cancerous growth; it begins as a tumor that causes the host's body to literally construct the infant creature from its own biological material.[1] This process causes the developing embryo to take on some of the host's physical traits via a process known as the DNA reflex,[2] including bipedalism, quadrupedalism[6] or even possessing the mandibles of a Predator[7] and other body structure changes. Over the course of 1–24 hours, and sometimes up to several days in the case of some Queens, the tumor develops into a Chestburster, at which point the creature emerges, violently ripping open the chest of the host, killing it. Owing to its cancerous nature, Chestburster development is typically fatal for the host even if the growing organism itself is surgically removed.[8]

Growth and maturity

Brett and Alien molted skin

Samuel Brett holding the Alien's molted skin.

Immediately after the Chestburster erupts from the body of its host, it will typically flee and find a secure location in which to molt into its adult form — at this stage in its life, the Xenomorph is in fact quite vulnerable. Initially, the Chestburster is less than 1 foot (30 cm) tall. However, it soon undergoes a dramatic growth spurt, reaching adult size in a matter of hours; aboard the Nostromo, the infant Alien grew to be over 7 feet (2.2m) in height by the time the crew located it again.[4]

Adult Castes


Main article: Drone
Xenomorph drone caste

A Drone.

The Drone is the most basic and common form of Xenomorph found in the Hive; the Drone form acts much like worker bees or ants. The Drones' main function is to keep the Hive functioning properly and to gather new hosts for impregnation. They are almost identical to Warriors in appearance with the exception of their smooth, domed skull, and their tails, which end in a stinger-like barb as opposed to a large blade.


Main article: Warrior
Warrior looks at Vasquez

A Warrior.

The Warrior (also called the Soldier or Hunter) is the primary assault caste of the Xenomorphs. They are fast, strong, reasonably tough, and savage combatants. Even in death the Warrior is dangerous, as its highly pressurised bloodstream will cause it to burst apart when killed and drench nearby enemies in acid. Warriors have ridged heads, as opposed to the smooth carapace of the Drone, but are otherwise virtually identical; because of this, Warriors are often said to simply be the mature life stage of the Drone.


Main article: Praetorian

A Praetorian.

Praetorians are considerably larger than most other adult Xenomorphs, typically around twice the size of a Warrior, but are smaller than Queens. They act as guards to the Queen within the Hive (their name taken from the Praetorian Guard, the loyal bodyguards who would protect the Emperor in Ancient Rome). They are easily distinguished by the large, flat crest, like a crown, that extends from the rear of their heads. It is thought Praetorians may be capable of molting into a Queen if no Queen is present. Praetorians possess much more concentrated acidic blood, and they have been seen to produce a deafening scream that will summon additional Warriors to their aid.[9]


Main article: Queen (caste)
Ripley finds Queen

Ellen Ripley encountering a Queen on Acheron (LV-426).

Xenomorph Queens are considered the apex of the species. They are significantly larger and stronger than basic Warriors and even Praetorians. They are approximately 20 feet tall when standing erect and 53 feet in length.[10] Their body structure differs also, having two pairs of arms, with a smaller secondary pair of limbs located on the chest. The Queen's head is larger than other adult Xenomorphs and is protected by a crest, similar to that on Praetorians but considerably larger. The exact shape of the crest can vary from Queen-to-Queen. Unlike other Xenomorphs, the Queen also has high heel protrusions from its feet.

Egg-laying Queens possess an immense ovipositor attached to their lower torso, similar to the enlarged abdomen of a queen termite. Unlike insect queens, there appears to be no need for drones to fertilize the Xenomorph Queen.[7][11] When attached to its ovipositor, the Queen is essentially immobile and her body is supported by a biomechanical "throne" that consists of a lattice of struts resembling massive insect legs.[9][12]


Main article: Jockey-Xenomorph

The Jockey-Xenomorph, also known as the Ultramorph,[13] is a Xenomorph born from an Engineer (its name being a reference to the colloquial name for the Engineers, "Space Jockeys"). The Jockey-Xenomorph is usually depicted as being huge in size, perhaps rivalling Queens in height. The Jockey-Xenomorph should not be confused with the Deacon, a creature born from a Trilobite impregnating an Engineer.


Main article: Predalien (caste)

A Predalien.

The Predalien is a Xenomorph spawned from a Yautja, or Predator. It is apparently rare and is regarded by the Yautja themselves as an abomination and an affront to their species.[9] Predaliens feature many traits in common with Yautja, such as dreadlock-like appendages on their heads, similar mandibles, and occasionally comparable skin color and vocalizations. They are large, bulky creatures, possessing greater physical strength than both Predators and human-spawned Xenomorphs. Predaliens also have thicker tails than regular Xenomorphs. At least one Predalien has been capable of bypassing the Ovomorph/Facehugger reproductive cycle altogether, being able to implant multiple embryos within a single host directly through its inner jaw. This trait apparently allows the creature to build an army of Drones or Warriors before it becomes a mature Queen and enters its sedentary condition with an ovipositor.

Predaliens notably take after their host to a greater extent than human-spawned Xenomorphs, possibly because the Predator's genetic code is significantly more potent. This could also explain why some Predaliens have been known to carry out ritualistic mutilation of their prey, perhaps as some form of instinctual throw-back to Yautja customs passed down genetically from the host.

Drukathi Xenomorph

Main article: Drukathi Xenomorph

A type of Xenomorph spawned from Drukathi. Much like Runners, these Xenomorphs are quadrupedal, but differed in their size and strength, which were far greater than either a Runner or a human-spawned Xenomorph. They have the ability to place themselves in a type of long-term hibernation, and in this stage, their complexions become statuesque. It is unknown if this ability is exclusive to this variation or the species at large, or if they were simply forced into this state by the Drukathi.[14]

Mutated Forms

Cloned Xenomorphs

Main article: Cloned Xenomorph

Cloned Xenomorph.

The Cloned Xenomorphs were a mutated Xenomorph strain bred aboard the USM Auriga by United Systems Military scientists in 2381.[15] They descended from the Queen extracted from the cloned Ellen Ripley, known as Ripley 8. Due to imperfections in the cloning process, the Queen and her offspring were not true Xenomorphs but subtly altered hybrids, mutated through the inclusion of human DNA in their genetic makeup.

While the Cloned Xenomorphs generally resembled normal human-spawned Xenomorphs, they possessed several notable differences that made them unique. Their necks were fleshier in appearance compared to the biomechanical look of other Xenomorphs, and they displayed some quadrupedal traits akin to the the Runner caste, as opposed to adopting the primarily bipedal stance of other human-spawned Xenomorphs. There were also slight differences in the shape of the head, which was narrower, with a longer muzzle and more prominent chin. Additionally, both the Cloned Queen and her Drones were green-brown in color, with a shimmering, insect-like quality to their mesoskeletons.


Main article: Newborn
Newborn 1

The Newborn.

The Newborn was a mutant human/Xenomorph hybrid creature created when the Queen aboard the USM Auriga developed a second reproductive cycle, a perversion of the human uterus (and related organs). The Newborn was considerably larger than a regular Xenomorph and notably does not possess the faceless, highly elongated skull typical of the species. Instead, it had a far more human-like face, including eyes, a nose, and a fleshy tongue in place of the Xenomorph's signature inner jaw, and a far more humanoid skull that showed only minor elongation at the rear. The creature also lacked the distinctive dark, biomechanical mesoskeleton common to the species, instead being covered in soft, flesh-colored skin. The Newborn possessed immense strength, able to jump huge distances or crush a man's skull with its bare hands. It shared little association with its Xenomorph brethren, going so far as to kill the Queen that bore it, and apparently viewed Ripley 8 as its true "mother".

Luiz-Xenomorph Hybrid

The Luiz-Xenomorph Hybrid was a horrific fusion between a Xenomorph and Luiz, a Hadley's Hope colonist who had fled to LV-223 to escape the Xenomorph infestion on Acheron aboard the Onager. LV-223 possessed a vast ecosystem accelerated by Chemical A0-3959X.91 – 15; said chemical polluted a lake at which Luiz was attacked by a Xenomorph and both were submerged in the water. The accelerant in the water promptly merged the two together into a single, chimera-like beast which attacked both humans and Xenomorphs alike. The creature killed many other Acheron colonists before it was finally killed.

Behind the Scenes

Eggmorphing: The original life cycle

Main article: Eggmorphing

In the initial cut of Alien, the Alien possessed a complete reproductive life cycle that did not require a Queen to lay more Eggs. Rather, the creature would cocoon its victims, dead or alive, in its Hive and subsequently convert them by unknown means into a new Egg containing a Facehugger, a process dubbed "Eggmorphing".[16]

This process allowed even a solitary Drone to continue the creature's existence. However, the scene showing this final stage was cut from Alien for reasons of pacing, leaving the ultimate origin of the Eggs in the film obscure. This in turn allowed Aliens director James Cameron to introduce a concept he had initially conceived for a spec script called Mother,[17] whereby a massive mother Xenomorph laid the Eggs and formed the basis for the creature's life cycle. Cameron conceived the Queen as a monstrous analogue to Ripley's own maternal role in the film.[17] In that vein, some critics have compared the Queen to Grendel's mother.[18][19]

Despite its deletion from the theatrical cut of Alien, the original life cycle was included in the novelization of the film,[20] while the movie footage was subsequently reintegrated in the Director's Cut from 2003.

The two methods of reproduction have never been reconciled in the films. However, the novelization of Alien3 suggests that both methods are typical of the species, and that the Eggmorphing seen in the Director's Cut of Alien is simply an alternate means for a Xenomorph to reproduce when a Queen is not present, or possibly even the means by which a Royal Facehugger is created.[21]


  1. 1.0 1.1 Dave Hughes, Lee Brimmicombe-Wood. Aliens, Vol. 2 #17, p. 43 (1993), Dark Horse International.
  2. 2.0 2.1 Sandy Schofield. Aliens: Rogue, p. 63 (1996), Bantam Spectra.
  3. S. D. Perry. Alien: The Weyland-Yutani Report, p. 14 (2014), Insight Editions.
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  14. Tim Lebbon. Alien: Out of the Shadows (2014), Titan Books.
  15. S. D. Perry. Alien: The Weyland-Yutani Report, p. 9 (2014), Insight Editions.
  16. Dan O'Bannon, Ronald Shusett (writers), Ridley Scott (director). Alien Director's Cut (2003), 20th Century Fox [DVD].
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  20. Alan Dean Foster. Alien, p. 210 (2014), Titan Books.
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