Parasites in fiction

Parasites appear frequently in biology-inspired fiction from ancient times onwards, with a flowering in the nineteenth century. These include intentionally disgusting 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. Some fictional parasites, like Count Dracula and Aliens Xenomorphs, have become well known in their own right. 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. The entomologist E. O. Wilson has characterised parasites as "predators that eat prey in units of less than one". 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". 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". Parasitism featured repeatedly as a literary motif in the nineteenth century, though the mechanisms, biological or otherwise, are not always described in detail. For example, the eponymous Beetle in The Beetle by Richard Marsh, 1897, is parasitic and symbolically castrates the human protagonist. 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. Parasites, represented as extraterrestrial aliens or unnatural beings, are seen in science fiction as distasteful, in contrast to (mutualistic) symbiosis, and sometimes horrible.