As in the question.

It is possible that there may be two species which are so interdependent that one is necessary for the other to breed. (Zombie ants come to mind, but this would be on a different scale). I am interested in whether the relationship between facehuggers and the full xenomorph is a case of "facehugger is a part of the life-cycle of a xenomorph" or a case of "two inter-dependent species".

(By the nature of symbiosis, it is also possible that these two started as independent species and have combined into one super-organism.)


Almost certainly. The different stages' reproduction produces each other (facehuggers come from eggs, the other stages come from facehugger "infestation") so I think by any meaningful definition they'd have to be the same species.

The reason it doesn't look like it at first is that the facehugger dies rather than transforming into the next stage. This isn't just a normal larva to adult metamorphosis. (The chestburster to "alien" transition would be a metamorphosis though.)

What seems to be going on is alternation of generations (which is a real thing, but mostly a plant thing on Earth - https://www.britannica.com/science/alternation-of-generations). Form A's reproduction produces a radically different Form B, which then produces Form A again.

  • +1 for the link. Btw, metagenesis sounds a lot cooler...
    – flq
    Sep 4 '16 at 21:51

Xenomorph starts life as an egg-like creature (first stage) which, when detecting the presence of a potential host, opens up to release the second stage: a small quasi-arachnoid life form (facehugger) which launches itself onto the host's face and impregnates it with an endoparasitoid larva, which later consumes the host from within and exits the body as a vaguely worm-like organism, which then grows very quickly, developing into the adult Xenomorph.

Wikia-Facehugger / Wikia-Xenomorph


I would argue that is highly impropable that the different stages are different species living in symbiosis (By the way your example isn't - as the ant has no benefit from being infected by the fungus). If they were different species every stage would have to carry the genome of every other stage which would be highly complicated to achive. I can't say it would be impossible though.

  • I know such mutually beneficial relationships exist in nature (especially in the cellular world), but not being a biologist I have difficulty thinking of one. The ant/fungus example may be a weaker one, but it was the first one I could think of which is relevant. Sep 4 '16 at 2:59

In the game Alien: Isolation, facehuggers end up all over the spaceship. They end up impregnating a member of the crew.


Throughout all this, there remains only one xenomorph on the ship. The xenomorph probably lays the facehuggers as eggs- as seen by the cluster of eggs at the start of Alien.

alien egg


Then, the face hugger creature impregnates a host, and a baby xenomorph is born.

  • 1
    That answer describes the already known reproduction cycle (and skips the Queen part), but doesn't even remotely answers the original question
    – Yasskier
    Sep 4 '16 at 20:27

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