The earworm, Lombricus auris, is a parasitic species of worm that can infect a large number of mammals. Rather small in size, earworms are deadly in most cases, and responsible for a number of deaths each year. Although infections of humans have decreased significantly since the worm was first discovered in 1892 by Dr. Humphrey Earbog, the worm population seems to be thriving nonetheless, probably through a rise in infections of animal hosts.
Earworms mate only once, at the beginning of their life, and after that, they start searching for a host. The host can be almost any mammal. The worms lodge themselves in the ear of their victim (hence the name), and start manipulating the auditory signals received by their hosts. They have special appendages, called ceruchus (latin for string), which they vibrate to produce a sound that hypnotizes their victims. The host is put into a sort of trance that will cause him to wander aimlessly, which will usually result in his death through accident, either by falling down a cliff, or being attacked by a predator, etc. The worm then lays its eggs in the dead body, which will serve as nutrients for the offspring once they hatch. The young worms will feed of the cadaver, and, after mating, leave in search for their own host.
The effects of the earworm have been described by a number of historic populations around the world, from the celts of ancient britain to the Indians of South-America, and it is believed that the earworm is present all over the world.
Even though cases of death have become rare in humans, and, with the advent of modern medecin, the infection can be treated since the 1980s, there has been a recent resurgence of interest in the species, driven mainly by the intelligence community, who is trying to reproduce the hypnotic effects of the worm's “song” for their own ends. Recent leaks of classified documents lead us to believe that there have been several attempts in this direction, from Britney Spears to Justin Bieber, but most of them seem to have obtained mediocre results at best.