When sweet little bees go to war

Tiny bees that couldn’t sting if their hives depended on it have revealed a new side of apian violence.

Little Tetragonula bees belong to the same family as honeybees but don’t have stingers. “They’re about the size of large ants — but much cuter,” says Paul Cunningham of Queensland University of Technology in Brisbane. In that region of Australia, two stingless bee species, T. hockingsi and T. carbonaria, thrive in backyard hives.

Hobbyists keep the two native pollinator species as pets — they’re good with children — and for their honey. It’s “very tangy and citrusy,” Cunningham says. Yet he and his colleagues now report that their endearing little neighbors are the first bees known to stage massive, days-long, high-casualty battles taking over nests of another bee species.

Battles between the two species are “spectacular,” the researchers say in the December American Naturalist. A cloud of attacking bees collides in midair with defenders that boil out of the nest. Combatants bite each other and drop to the ground. “An attacking bee grabs a defender, and they hold on until they die,” Cunningham says. “Underneath the hive you get this carpet of bees.”

While females wrestle to the death, male drones gather nonviolently, sometimes with drones from the opposing side. “They’re like ‘Yeah, yeah, come on — let’s all just hang out on this branch,’ ” Cunningham says.

The generally calm T. carbonaria bees were already known to attack another colony of their own kind now and then. That’s what Cunningham first thought he was seeing as he monitored a hive that withstood two swarming attacks lasting for days at a time, only to crumble in the third invasion.

But genetics revealed the attackers to be almost all T. hockingsi, says coauthor James Hereward of the University of Queensland in Brisbane. A closer look at dozens of other hives revealed that both species do takeover raids.

Because each bee grappling with an opponent usually brings death to them both, stingless wars mean massive casualties. Perhaps the benefit that outweighs the carnage comes from invaders’ ability to spread genes of one of their own young queens, who moves into an already provisioned hive. What drives battles, in bees as in another warlike species, may be the prize of thrones.