I've been a fan of the "Alien" films for as long as I've been old enough to watch them -- probably a little longer to be honest. So it was a huge thrill to explore the xenomorphs in true HowStuffWorks fashion.
Elsewhere on the Net, you'll find any number of fan-generated articles on speculative alien biology, as well as some excellent resources about the making of the films. I tried to steer somewhere between the two and turned to real-world biology whenever possible, rather than the conflicting world of comics, novelizations, video games and "Predator" crossovers.
There's also quite a bit of fascinating film study on the "Alien" franchise out there, discussing everything from the sexual aspects of the creature itself to academic debate over Ripley's underwear. If you'd like to catch up on some of that, do check out the Stuff to Blow Your Mind episode "The Science of Prometheus."
I'd like to personally thank H.R. Giger, who was very generous in sharing information and artwork for this article. Be sure to visit the H.R. Giger Museum, in Gruyeres, Switzerland, where the artist's original "Alien" paintings can be viewed in person year-round. And if you want to dive into every possible detail regarding the making of "Alien," then check out the artist's own book, "Giger's Alien," Valaquen's blog Strange Shapes and Ian Nathan's book "Alien Vault: The Definitive Story of the Making of the Film."
- Blow Your Mind: The Science of "Prometheus"
- How Bees Work
- How Wasps Work
- How Aliens Work
- How Whales Work
- How Evolution Works
- How Human Reproduction Works
- How Frankenstein's Monster Works
- How Ghouls Work
- "Alien." 20th Century Fox. 1979.
- "Alien3." 20th Century Fox. 1992.
- "'Alien' Jaws Help Moray Eels Feed." Science Daily. Sept. 6, 2007. (Aug. 11, 2012) http://www.sciencedaily.com/releases/2007/09/070905134523.htm
- "Alien Resurrection." 20th Century Fox. 1997.
- "Aliens." 20th Century Fox. 1986.
- "Anatomy of the Zenomorph." Aliens vs. Predator: Requiem Extended Edition DVD. 20th Century Fox. 2007.
- Cornell University. "Both Arthropods And Vertebrates Have Evolved Hard, Jointed Skeletons." (Aug. 11, 2012) http://www.biog1105-1106.org/demos/105/unit10/10a.skeletons.html
- Dengler-Crish, Christine M. and Kenneth C. Catania. "Cessation of Reproduction-Related Spine Elongation After Multiple Breeding Cycles in Female Naked Mole-Rats." Anat Rec (Hoboken). January 2009. (Aug. 11, 2012) http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2864304/
- Giger, H.R. "Giger's Alien." Morpheus International. Oct. 4, 1994.
- Gill, Victoria. "Ants inhabit 'world without sex.'" BBC News. April 15, 2009. (Aug. 11, 2012) http://news.bbc.co.uk/2/hi/science/nature/7998931.stm
- Levy, Frederick Albert. "H.R. Giger Alien Design." Cinemafantastique. 1979.
- Lynch, Mike. "The Anchorpoint Essays." June 30, 2008. (Aug. 11, 2012) http://www.anchorpointessays.com
- McDarby, Michael. "An Online Introduction to the Biology of Animals and Plants." Fulton-Montgomery Community College. 2012. (Aug. 11, 2012) http://faculty.fmcc.suny.edu/mcdarby/animals&plantsbook/animals/07-Arthropods.htm
- Nathan, Ian. "Alien Vault: The Definitive Story of the Making of the Film." Voyageur Press. Sept. 17, 2011.
- National Wildlife Federation. "Blue Whale." 2012. (Aug. 11, 2012) http://www.nwf.org/Wildlife/Wildlife-Library/Mammals/Blue-Whale.aspx
- Nelson, Davia and Nikki Silva. "A Termite Queen and Her Ultimate Sacrifice." NPR. May 6, 2011. (Aug. 11, 2012) http://www.npr.org/2011/05/06/136028437/a-termite-queen-and-her-ultimate-sacrifice
- Salisbury, Mark. "Prometheus: The Art of the Film." Titan Books. June 12, 2012.
- Taylor, Christopher. "Eating Mum from the Inside Out." Catalogue of Organisms. Nov. 20, 2008. (Aug. 11, 2012) http://coo.fieldofscience.com/2008/11/eating-mum-from-inside-out.html