Parasites by Katrin Alvarez. Oil on canvas, 2011

Parasites appear frequently in biology-inspired fiction from ancient times onwards, with a flowering in the nineteenth century.[1] These include intentionally disgusting[2] alien monsters in science fiction films, often with analogues in nature. Authors and scriptwriters have, to some extent, exploited parasite biology: lifestyles including parasitoid, behaviour-altering parasite, brood parasite, parasitic castrator, and many forms of vampire are found in books and films.[2][3][4][5] Some fictional parasites, like Count Dracula and Alien's Xenomorphs, have become well known in their own right.


Parasitism in nature is a biological relationship in which one species lives on or in another, causing it harm.

Further information: Parasite

In evolutionary biology, parasitism is a relationship between species, where one organism, the parasite, lives on or in another organism, the host, causing it some harm, and is adapted structurally to this way of life.[6] The entomologist E. O. Wilson has characterised parasites as "predators that eat prey in units of less than one".[7] According to the immunologist John Playfair, the term 'parasite' is distinctly derogatory in common usage, where a parasite is "a sponger, a lazy profiteer, a drain on society".[8] The idea is however much older. In ancient Rome, the parasitus was an accepted role in Roman society, in which a person could live off the hospitality of others, in return for "flattery, simple services, and a willingness to endure humiliation".[9][10]


Nineteenth century novels

Bela Lugosi as the vampire Count Dracula, 1931

Parasitism featured repeatedly as a literary motif in the nineteenth century, though the mechanisms, biological or otherwise, are not always described in detail.[11] For example, the eponymous Beetle in The Beetle by Richard Marsh, 1897, is parasitic and symbolically castrates the human protagonist.[11] Bram Stoker's 1897 Dracula starts out as an apparently human host, welcoming guests to his home, before revealing his parasitic vampire nature. Conan Doyle's Parasite, in his 1894 book The Parasite, makes use of a form of mind control similar to the mesmerism of the Victorian era; it works on some hosts but not others.[12]

Science fiction

Parasites, represented as extraterrestrial aliens or unnatural[13] beings, are seen in science fiction as distasteful,[13] in contrast to (mutualistic) symbiosis, and sometimes horrible.[13] Practical uses can be made of them, but humans who do so may be destroyed by them.[13] For example, Mira Grant's 2013 novel Parasite envisages a world where people's immune systems are maintained by genetically engineered tapeworms.[14] They form readily understood[13] characters, since, as Gary Westfahl explains, parasites need to exploit their hosts to survive and reproduce.[13]

The social anthropologist Marika Moisseeff argues that Hollywood science fiction favours insects as villain characters because of their parasitism and their swarming behaviour. Such films, she continues, depict the war of culture and nature as "an unending combat between humanity and insect-like extraterrestrial species that tend to parasitize human beings in order to reproduce."[4]


Among the many types of fictional parasite are the mitochondria of Parasite Eve; these are energy-generating organelles in animal cells, imagined as parasitic.

The range of accounts of fictional parasites and the media used to describe them have greatly increased since the nineteenth century, spanning among other things literary novels, science fiction novels and films, horror films, and video games.[11][3][5][15] The table illustrates the variety of themes and approaches that have become possible.

Examples of the range of accounts of fictional parasites and their biological counterparts
Author Work Medium Date Parasite Effect Biological counterpart
David Cronenberg Shivers Science fiction body horror film 1975 Genetically engineered Useful in organ transplants; sexually transmitted and aphrodisiac when modified by a deranged scientist Genetic engineering and its ethical implications[16]
Metroid Video game 1986 X Parasite Deadly infection; confers useful energy and powers to vaccinated people Pathogens such as bacteria, viruses; vaccines[15][17]
Hideaki Sena (pharmacologist) Parasite Eve Science fiction horror novel 1995 Mitochondria cut free from mutualism in human cells Deadly parasitism Mitochondria, power-generating organelles, formerly free-living prokaryotic organisms, became mutualistic by symbiogenesis c. 2 billion years ago[18][19][20]
Irvine Welsh Filth Novel 1998 Talking tapeworm Sinister, comic;[21] "the most attractive character in the novel"; becomes the sociopathic policeman's alter ego and better self.[22] Tapeworms, intestinal parasites[22]

Fiction and reality

Emerald cockroach wasp (left) "walking" a paralyzed cockroach to its burrow

Kyle Munkittrick, on the Discover magazine website, writes that the great majority of aliens, far from being as strange as possible, are humanoid.[23] Ben Guarino, in The Washington Post, observes that despite all the "cinematic aliens' gravid grotesquerie",[2] earthly parasites have more horrible[2] ways of life. Guarino cites parasitic wasps that lay their eggs inside living caterpillars, inspiring A. E. Van Vogt's 1939 story "Discord in Scarlet", Robert Heinlein's 1951 novel The Puppet Masters, and Ridley Scott's 1979 film Alien.[2] The eponymous Alien has a "dramatic"[2] life-cycle. Giant eggs hatch into face-huggers that grasp the host's mouth, forcing him to swallow an embryo. It rapidly grows in his intestines, soon afterwards erupting from his chest and growing into a gigantic predatory animal resembling an insect. Guarino cites the parasitologist Michael J. Smout as saying that the "massive changes"[2] are feasible, giving the example of flatworms that transform from an egg to a tadpole-like form to an infective worm.[2] The biologist Claude dePamphilis agrees, too, that parasites can acquire genes from their hosts, giving as example a broomrape plant that had taken up genes from its host on 52 occasions, having thoroughly overcome the host plant's defences. They suggest further themes for future science fiction films, including emerald jewel wasps that turn cockroaches into subservient puppets, able to crawl but unable to act independently; or the barnacle-like crustaceans that castrate their crab hosts, or grow into their brains, altering their behaviour to care for the young barnacles.[2] All the same, a 2013 poll of scientists and engineers by Popular Mechanics magazine revealed that the parasite-based science fiction films The War of the Worlds (Byron Haskin, 1953) and Alien were among their top ten favourites.[24]

Types of parasite

Robert A. Heinlein's behaviour-altering The Puppet Masters on the cover of the September 1951 issue of Galaxy Science Fiction

Further information: Parasitism § Major strategies

Several types of parasite, corresponding more or less accurately to some of those known in biology, are found in literature.[25] These include haematophagic parasites (fictional vampires), parasitoids, behaviour-altering parasites, brood parasites, parasitic castrators, and trophically transmitted parasites, as detailed below.

Haematophagic parasite

Further information: Vampire

In ancient times, myths of blood-drinking demons were widespread, including Lilith who feasted on the blood of babies.[26]

Fictional vampireshaematophagic parasites—began in the modern era with Count Dracula, the title character of Bram Stoker's 1897 gothic horror novel Dracula, and have since appeared in many books and films ranging from horror to science fiction. Along with the shift in genres went a diversification of life-forms and life-cycles, including blood-drinking plants like the "strange orchid" in The Thing from Another World, aliens like H. G. Wells's Martians in The War of the Worlds, "cyber-vamps" like "The Stainless Steel Leech" and "Marid and the Trail of Blood", and psychic bloodsuckers, as in Arthur Conan Doyle's The Parasite and Robert Wiene's 1920 film The Cabinet of Dr. Caligari.[12][27]


Further information: Parasitoid

A 1990s gargoyle at Paisley Abbey resembling a Xenomorph[28] parasitoid from Alien[29]

The Xenomorph in Alien is a parasitoid, inevitably fatal to its human host. It has a life-cycle stage that grows inside the person's body; when mature, the predatory adult Xenomorph bursts out, killing the host. This behaviour was inspired by parasitoid wasps which have just such a life-cycle.[25][30][31]

The molecular biologist Alex Sercel compares Xenomorph biology to that of parasitoid wasps and nematomorph worms, arguing that there is a close match.[30] Sercel notes that the way the Xenomorph grasps a human's face to implant its embryo is comparable to the way a parasitoid wasp lays its eggs in a living host. He compares the Xenomorph life cycle to that of the nematomorph Paragordius tricuspidatus, which grows to fill its host's body cavity before bursting out and killing it.[30]

The marine biologist Alistair Dove writes that there are multiple parallels between Xenomorphs and parasitoids, though there are in his view more disturbing life cycles in real biology.[32] He identifies parallels include the placing of an embryo in the host; its growth in the host; the resulting death of the host; and alternating generations, as in the Digenea (trematodes).[32]

Behaviour-altering parasite

Further information: Behaviour-altering parasite and Human possession in science fiction

Mind-controlling parasites feature in twentieth century science fiction. In Robert A. Heinlein's 1951 The Puppet Masters, slug-like parasites from outer space arrive on Earth, fasten to people's backs and seize control of their nervous systems, making their hosts the eponymous puppets.[1] In Star Trek II: The Wrath of Khan, the Ceti eel tunnels into the ear of its human host until it reaches the brain. This is a behaviour-altering parasite analogous to Toxoplasma gondii, which causes infected mice to become unafraid of cats. This makes them easier to catch and consume and, once an infected mouse has been eaten, the parasite will then infect the cat, its definitive host, in which it can reproduce sexually.[25] The Goa'uld in Stargate SG-1 enters through the host's neck and coils around the host's spine, assuming control.[25][33] The Slug/Squid alien in The Hidden similarly enters via the host's mouth before taking over its body.[33]

Brood parasite

Brood parasites lay their eggs in other birds' nests for them to raise, inspiring the science fiction novel The Midwich Cuckoos.

Further information: Brood parasite

Brood parasitism is not a common theme in fiction. An early example was John Wyndham's 1957 novel The Midwich Cuckoos, which sees the women of an English village give birth to and then bring up a group of alien children. The aliens are telepathic, and intend to take over the world. In nature, brood parasitism occurs in birds such as the European cuckoo, which lay their eggs in the nests of their hosts. The young cuckoos hatch quickly and eject the host's eggs or chicks; the host parents then feed the young cuckoos as if they were their own offspring, until they fledge. As a plot device, this allows aliens and humans to interact closely.[13][34][35] A somewhat similar approach is taken in Octavia E. Butler's 1987–1989 Lilith's Brood, but the offspring born to the human mother there is an alien-human hybrid rather than simply an alien.[36][37]

Parasitic castrator

Sacculina, a parasitic castrator (highlighted), inspired Philip Fracassi's novella of that name.

Further information: Parasitic castrator

Parasitic castration is found in nature in greatly reduced parasites that feed on the gonads of their crab hosts, making use of the energy that would have gone into reproduction. It is seen in fiction in Philip Fracassi's 2017 horror novella Sacculina, named for a genus of barnacle-like crustaceans with this lifestyle.[38][39] It tells the tale of a chartered fishing boat, far from home, that is overrun by parasites from the deep.[40]

Trophically-transmitted parasite

Pork tapeworm, an intestinal parasite transmitted via human faeces to pigs, and back to humans via inadequately-cooked meat

Further information: Tapeworm, Parasite (Grant novel), and Filth (novel) § The Tapeworm

The genetically engineered tapeworm in Mira Grant's novel Parasite, and the talking tapeworm in Irvine Welsh's novel Filth, are fictional versions of conventional intestinal parasites.[14][22] Tapeworms have complex life-cycles, often involving two or more hosts of different species, and are transmitted as the eggs are passed in faeces and eaten by another host, only for the host to be eaten, passing the parasite on to the predator.[41] The unattractive lifecycle allows the novelists to exploit their readers' emotional reactions to the parasites. The parasite in Welsh's novel has been described as a "kind of sinister but strangely comic element".[21]

See also


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  2. ^ a b c d e f g h i Guarino, Ben (19 May 2017). "Disgusting 'Alien' movie monster not as horrible as real things in nature". The Washington Post.
  3. ^ a b Glassy, Mark C. (2005). The Biology of Science Fiction Cinema. McFarland. pp. 186 ff. ISBN 978-1-4766-0822-8.
  4. ^ a b Moisseeff, Marika (23 January 2014). "Aliens as an Invasive Reproductive Power in Science Fiction". HAL Archives-Ouvertes: 239.
  5. ^ a b Williams, Robyn; Field, Scott (27 September 1997). "Behaviour, Evolutionary Games and .... Aliens". Australian Broadcasting Corporation. Retrieved 30 November 2017.
  6. ^ Poulin, Robert (2007). Evolutionary Ecology of Parasites. Princeton University Press. pp. 4–5. ISBN 978-0-691-12085-0.
  7. ^ Wilson, Edward O. (2014). The Meaning of Human Existence. W. W. Norton & Company. p. 112. ISBN 978-0-87140-480-0. Parasites, in a phrase, are predators that eat prey in units of less than one. Tolerable parasites are those that have evolved to ensure their own survival and reproduction but at the same time with minimum pain and cost to the host.
  8. ^ Playfair, John (2007). Living with Germs: In health and disease. Oxford University Press. p. 19. ISBN 978-0-19-157934-9. Playfair is comparing the popular usage to a biologist's view of parasitism, which he calls (heading the same page) "an ancient and respectable view of life".
  9. ^ Matyszak, Philip (2017). 24 Hours in Ancient Rome: A Day in the Life of the People Who Lived There. Michael O'Mara. p. 252. ISBN 978-1-78243-857-1.
  10. ^ Damon, Cynthia (1997). "5". The Mask of the Parasite: A Pathology of Roman Patronage. University of Michigan Press. p. 148. ISBN 978-0-472-10760-5. A satirist seeking to portray client misery naturally focuses on the relationship with the greatest dependency, that in which a client gets his food from his patron, and for this the prefabricated persona of the parasite proved itself extremely useful.
  11. ^ a b c Jajszczok, Justyna (2017). The Parasite and Parasitism in Victorian Science and Literature (PDF). University of Silesia (dissertation). Retrieved 10 June 2018.
  12. ^ a b Hutchison, Sharla; Brown, Rebecca A. (2015). Monsters and Monstrosity from the Fin de Siècle to the Millennium: New Essays. McFarland. pp. 2–12. ISBN 978-1-4766-2271-2.
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  34. ^ Adams, Stephen (4 January 2009). "Cuckoo chicks dupe foster parents from the moment they hatch". The Daily Telegraph. Archived from the original on February 13, 2009. Retrieved 17 June 2018.
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