GIANT honeybees may be genetically guided back to their old haunts. Two groups of researchers have found that migrating swarms of the bees return each year to the same trees to build their nests, even though all the old scouts that decided where to set up home have died in the intervening seasons.
“The results are wonderful. The academic community will be delighted,” says Justin Schmidt, a research entomologist at the Carl Hayden Bee Research Center in Tucson, Arizona. The findings are especially surprising because giant honeybees, Apis dorsata, migrate enormous distances in search of food. Studies in Sri Lanka have shown that the bee colonies follow the flowering seasons between the highlands and the lowlands, sometimes covering up to 200 kilometres. But no matter the distance, they still make their way back home.
Entomologist Peter Neumann of Rhodes University in Grahamstown, South Africa, and his colleagues analysed the genetic identities of five bee colonies nesting in Tenom, Malaysia, in 1995 and 1997. They found that one colony, headed by the same queen, nested at the same site in both years. At two other sites, daughter colonies returned in 1997 to nest at their maternal home of two years earlier.
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In another study, biologist Ben Oldroyd of the University of Sydney, Australia, and his team monitored 17 colonies at two sites in the Indian state of Assam. Four colonies headed by the same queens came back the following season, with one queen returning with her brood to the same location in subsequent years.
“Regular seasonal migrations are widespread in the animal kingdom, but active and directed migration is relatively rare in insects,” says Jürgen Paar, a member of Oldroyd’s team. He says that their findings provide the first proof that individual insects – in this case the queens – return to the same site.
But the job of scouting for nest sites falls to certain worker bees – and none of them would survive to the next migration season. “We assume migration is exhausting for the bees. It seems unlikely that any workers survive the whole time to return to the nest site,” says Paar. So how do the bees find their way home?
Neumann suggests a number of mechanisms to explain the phenomenon. Different colonies may be genetically programmed to begin their journeys at different times. Those arriving first may simply choose the most attractive sites, which are usually the same year after year, or select the remains of old combs, which bees prefer to new sites. Descendants of the old scouts may also be “genetically” attracted to the same locations in subsequent years. “All potential mechanisms must be genetic because the old workers have died,” says Neumann.
Entomologist Robert Page of the University of California, Davis, says that researchers will need to explore all possible explanations. “This is a biologically fantastic result,” he says.
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