Scientists feeding alcohol to fruit flies in an experimental “flypub” have demonstrated that, once intoxicated, the sexual inhibitions of male fruit flies are loosened and the flies begin to demonstrate a willingness to copulate with the same sex. They even have orgies.
The temperature-triggered release of the brain chemical dopamine was identified as the key element behind the change in behavior.
Check out the videos here.
More on that six beer theory here (warning NSFW).
Randy flies reveal how booze affects inhibitions [new scientist]