behind the scenes - Is the Xenomorph life cycle based on the life cycle of a real world species?

The Xenomorph life cycle is quite complex. It basically boils down to this¹:

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  Queen Xenomorph lays eggs.

  
  


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  Eggs hatch into facehuggers.

  
  
  


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  Facehuggers implant eggs in a host organism's throat.

  
  


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  Implanted eggs hatch into chest-bursters.

  
  


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  Chest-bursters grow into adult Xenomorphs. Their primary function appears to be serving the queen, protecting her eggs, and gathering host organisms and trapping them in the hive, where they can be easily implanted with facehugger eggs.

  
  

Although there are some parallels to real life social insect colonies, like ants, for example, this life cycle seems somewhat unique in that there are at least two different forms of life involved in the process: Facehuggers and Xenomorphs. If queens are distinct from other xenomorphs, that makes three different forms of life.

The most striking feature of the Xenomorph life cycle (and the part I am most interested in) is the facehugger: whereas most organisms go from being eggs to being babies/larvae to being adults, xenomorphs have a totally distinct sub-species, which is clearly not a Xenomorph itself, but is absolutely vital to the propagation of the species. That is to say, Facehuggers don't grow up, they don't turn into xenomorphs, and xenomorphs don't turn into Facehuggers, but you can't get a Xenomorph without first having a facehugger.

By way of comparison, a parasitoid wasp is always a wasp. The adult lays eggs in a host organism, the eggs hatch into larvae, the larvae metamorphosize into adult wasps, and so on. But xenomorph queens lay facehugger eggs, and Facehuggers lay Xenomorph eggs. Facehuggers don't resemble xenomorphs in any way, and vice versa. Xenomorph queens can't lay Xenomorph eggs. Only Facehuggers can do that. Facehuggers can't lay facehugger eggs. Only Xenomorph queens can do that.

Did Ridley Scott model the Xenomorph life cycle after a real world species, or did he just make the whole thing up himself?

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¹ _{I know that the director's cut of the first Alien movie shows people being turned into eggs, but I decided not to mention it because it would only muddy the waters without substantially changing the thrust of the question.}

Answer

TL;DR: Not entirely. The Xenomorph lifecycle appears to be a mash-up of several actual lifecycles - mostly insects & parasites, yet isn't 100% identical to any particular one.

Writer Dan O'Bannon's original lifecycle was based on a variety of different insects, and was also very similar to parasites like M. ancylivorus.

1. Adult lays the egg on a host


2. Egg hatches the parasitic larva, which burrows into the host


3. Larva uses host to gestate & form cocoon


4. Juvenile version of adult insect hatches from cocoon

This is nearly identical to O'Bannon's original Xenomorph lifecycle:

1. Adult creates the egg


2. Egg hatches the face-hugger, which finds a host & implants embryo



3. Embryo uses host to gestate & grow


4. Juvenile version of adult Xenomorph hatches from host

In fact, O'Bannon has said that parasitic insects were his primary inspiration:

When Dan O’Bannon started conceptualising his alien creature he turned to two key influences: the creatures depicted in the comic books he devoured as a child, and the insect world. “Works of fiction weren’t my only sources,” he explained in his essay Something Perfectly Disgusting. “I also patterned the Alien’s life cycle on real-life parasites … Parasitic wasps treat caterpillars in an altogether revolting manner, the study of which I commend to anyone who is tired of having good dreams.”...

and director Ridley Scott has also quoted insects as the inspiration behind the creature:

In the 1999 DVD commentary, Ridley Scott explains: “The whole notion of this [creature] was taken off a certain kind of insect that will find a host, lay its eggs, and then in that host it will bury its eggs, and then of course the eggs will grow and consume the host. So that’s the logic of it all. Probably what makes a lot of nature go around.”

Note that the extra "phase" of the Alien Queen was introduced in the sequel, with which O'Bannon had no involvement. James Cameron felt that Ripley needed an "equal" to face in the film's climax, and subsequently designed the giant Queen to fit that need. The Queen concept does, however, stick with the same insect motif.