Anthills and termite mounds often have castes of "soldiers," whose only goal in life is to defend the nest. That distinguishes them from beehives and wasp nests, where each individual holds a variety of jobs — including guard duty — throughout its life.
But now, thanks to a new study by researchers in Brazil and the U.K., we have the first-known example of true soldier bees. The scientists studied a common species of Brazilian bee called Tetragonisca angustula, aka "Jatai" in its native country, and found a distinct "soldier caste" that seems born for the sole purpose of hive security.
"The discovery is significant in terms of the evolution of advanced insect societies," the researchers explain in a statement released this week by the University of Sussex. "Large-bodied soldier workers have long been known in ants and termites, but this is the first evidence of a soldier bee — a worker physically designed for active defense of the nest."
While honeybees typically spend just one day guarding the hive before moving on to other jobs, about 1 percent of all Jatai bees are born as soldiers, which are 30 percent heavier than other workers, with larger legs and smaller heads. They also skip the traditional worker-bee duties, instead spending up to three weeks either standing or hovering vigilantly outside the nest's entrance (see video below).
Jatai bees don't have stingers, perhaps one reason why they breed full-time soldiers. These guards' heavier bodies and larger legs make them adept at fighting one of the species' main enemies: the "robber bee" Lestrimelitta limao, which can kill off entire Jatai colonies — up to 10,000 bees — as it raids them for food.
The stingless soldiers are missing a quintessential bee weapon when they take on such attackers, but that doesn't deter them. Hive defense is a suicide mission, in which a soldier clamps its head onto the wings of a robber bee, preventing it from flying. The soldier eventually dies, but its body remains clamped onto the intruder like an anchor, rendering it unable to attack the hive (see video below).
"Stingless bees are not defenseless," says study co-author and University of Sussex researcher Francis Ratnieks. "Jatai is one of the most common bees found in Brazil, but its sophisticated defenses make it one of the most amazing."
The study, conducted by scientists from the University of Sussex and the University of São Paulo, was published in the Proceedings of the National Academy of Sciences.
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