Africanized honey bees, known colloquially as "killer bees", are some hybrid varieties
of the Western honey bee species, (Apis mellifera), produced originally by cross-breeding
of the African honey bee with various European honey bees such as the Italian bee.
The hybrid bees are far more aggressive than any of the various European subspecies.
Small swarms of Africanized bees are capable of taking over European honey bee hives
by invading the hive and establishing their own queen after killing the European
The Africanized honey bees in the Western Hemisphere are of mixed descent from 26
Tanzanian queen bees of A. m. scutellata, accidentally released by a replacement
bee-keeper in 1957 near Rio Claro, São Paulo, in the southeast of Brazil, from hives
operated by biologist Warwick E. Kerr, who had interbred honey bees from Europe and
southern Africa. Hives containing these particular queens were noted to be especially
defensive. Kerr was attempting to breed a strain of bees that would produce more
honey and be better adapted to tropical conditions (i.e., more productive) than the
European subspecies of honey bee used in South America and southern North America.
The hives the bees were released from had special excluder grates to prevent the
larger queen bees and drones from getting out and mating with local queens and drones
of European descent. However, following the accidental release, the African queens
and drones mated with domesticated local non-African queens and drones, and their
descendants have since spread throughout the Americas. *