The history of Parasite is a long and complicated affair, and so this page gives you a choice between the short answer and the longer answers to questions people normally ask...
But first, the basics:

Parasite were formed in 1998 by Adam Scanlon and Deok-jin Joo, two schoolchildren living in Guildford, England. They were joined almost immediately after by Rupert Handley. After many years and lineup changes including Deok-jin moving back to his home country of South Korea, Rupert leaving and a stint when Adam was the only remaining band member the band settled on being a duo of Adam Scanlon and Iain Ballantine in late 2001 with Scanlon handling the keyboard, drummachine and vocal duties and Ballantine taking care of the bass and guitar. Some experiments were made in recording including the the completion of several self-produced singles, EPs and an album called The Infection which were sold to friends. Rupert Handley returned on guitar in 2003 and Ballantine left in 2004. Will Saunders joined Parasite on bass in September 2004 and by January the band were back down to a duo. The Scanlon/Saunders has proved the most stable lineup thus far after lasting three years. The duo recorded two more albums to sell to friends and their small but growing fanbase, The Ancient Modern and The Spring Collection both in 2005. Also in 2005 Parasite started gigging properly, and in 2006 work began with producer Ben Turk on new material. In 2007, with the old recordings now merely classed as demos, Parasite began releasing their music to the general public starting with the download-only single  Master Yoga. The follow-up single You Wouldn't Believe Me... If It Wasn't True was released in October 2007 on the bands own Parasite Stuff Recordings label. On the 9th January 2008 Will Saunders decided to leave the band over creative differences. Amid unsuccessful attempts to find a stable enough lineup a further single, Infrared, was released in February and finally in May the eventual release of the parent album Out With The New. In November 2008 during the recording of the forthcoming Second Sight album, performed and produced almost entirely by Adam, an evidently undeterred Scanlon met one Bob Williams who soon joined Parasite on guitar and currently graces the stage with his presence, and features on one track on the new album for one beautiful chord....