Brain protein fragments spur honey bees to be more aggressive.

Solvin Zankl/Minden Pictures

What turns bees into killer bees?

By Elizabeth Pennisi

Biochemists have tracked down the brain chemicals that make so-called killer bees such ferocious fighters. The compounds, which seem to be present in higher levels in the much-feared Africanized honey bee, can make less aggressive bees turn fierce, according to a new study. The compounds may also play a role in aggression in other animals—indeed, they’ve already been shown to do so in fruit flies and mice.

“This is another example of how behavior evolves in different species by using common molecular mechanisms,” says Gene Robinson, an entomologist and director of the University of Illinois’s Carl R. Woese Institute for Genomic Biology in Urbana, who was not involved in the work…