Umbrella began using their newly-developed t-Virus strains on animals soon after their founding. However, they were met with problems with their practicality, such as a lack of intelligence or insufficient strength increases which eliminated the Web Spinner as a reliable weapon. In its place, the Chimera project was started, which intended to graft insect DNA into human zygotes. Homeless women were abducted by Umbrella agents and forcibly impregnated with the modified zygotes. Out of various insect-human hybrids that were envisioned as bioweapons, it was a fly-human hybrid that was chosen for continued study. It was subsequently cloned to produce identical bioweapons.[excerpt 1]
Due to their many flaws, further research into more advanced forms was never conducted, and the Chimera's basic form was never refined to the lengths of the Hunter or the Tyrant.
Several Chimeras were encountered by the S.T.A.R.S. members during the Mansion Incident. In addition, Albert Wesker, shortly after regaining consciousness after the Tyrant "killed" him, encountered a Chimera while attempting to escape, only to effortlessly kill it with a single kick due to his newfound superhuman abilities.
Still, Umbrella continued at least a limited production of Chimeras in other facilities for a number of years, as several were discovered during Chris and Jill's raid on their Caucasus Laboratory, as well as during Wesker's own raid on the facility.