In the 1950s, Brazilians tried to jumpstart their honey industry using European bees. However the European bees didn't adapt well to the Brazilian climate. African bees, much better adapted to the environmental extremes of many of the areas interested in commercial beekeeping, were imported in hope that they would become a commercially viable species. African bees tend to be 10% smaller than European bees. Additionally, they are 25% lighter, they reproduce earlier, and they have a shorter lifespan.
At the time, the prospective beekeepers were unaware of the fact that African bees tend to be much more fierce, dominant, and aggressive than the European bees. In addition, African bees tend to be nomadic, which meant that they readily left manmade hives, moved into the jungles and establishing their own colonies away from human habitation.
Behaviorally, African bees tend to be offensive, rather than defensive, when other organisms come into close proximity of their hives. In fact, the defensive response of a single bee causes a rapid response so that suddenly and severely that the organism may experience attack by hundreds of bees. Africanized bees may pursue invaders for hours after the organism under attack has left the immediate hive area. Though the venom is virtually identical to that of European bees, the intensity of the attack and the volume of venom that the invading organism experiences led to the popular press designating Africanized bees as "killer bees."
These aggressive bees rapidly took over European bee colonies with three years of their initial Brazilian introduction. In contrast to the European bees, Africanized bee honey harvest is unpleasant and may be dangerous, while the yield is unreliable.
Africanized bees expanded their range to Venezuela in1973, Mexico in 1986, and established some colonies in the U.S. by 1990. They now can be found in New Mexico, Arizona, Nevada, and California (Bishop, 2005).