The whitefly is a major agricultural pest, and over the last six years Southwest of America has seen the near total infection of the species by a symbiotic bacteria, which makes them super-breeders. The bacterium Rickettsia bellii was originally spotted in just a few specimens in 2000, but by 2006 was in 97% of the bugs. How did it spread so widely, so fast? The bacterium supercharged the the infected insects, and those carrying the symbiont had more offspring, developed faster, and were more likely to survive than the uninfected. The symbiont is passed on through the mothers and tweaked the infected to have a higher percentage of female offspring.
This is one of the few times a symbiotic invasion of a host species has been observed. The research shows just how fast it can happen, and how much it can change both the biology and behavior of an organism.
And of course, it gives us ideas about what kind of genetically-modified bacteria mad scientists should be releasing into the water supply to create an army of sex slaves.