Honeybees use right antennae to tell friend from foe

To avoid a scuffle, a wayward honeybee might do best to stay on a stranger’s left. That’s because honeybees preferentially use their right antenna to distinguish between compadres and intruders, researchers report June 27 in Scientific Reports.

Scientists knew that the bees’ left and right antennae picked up different sensory cues, but the new work makes clear that this asymmetry extends into how bees navigate social situations.

The study also helps scientists understand a “big and interesting question: Why are our brains asymmetric?” says honeybee physiologist Julie Mustard of Arizona State University in Tempe. “The idea is that asymmetries allow the brain to have more area for processing complex information.”

Honeybee antennae are blanketed with a jungle of hairlike sensilla, microscopic protrusions housing neurons that transmit sensory information to the brain. Compared with the left antenna, the right contains more sensilla dedicated to smell, known to play a key role in honeybee communication.

To find out whether lopsidedness would influence behavior, researchers led by Giorgio Vallortigara of the University of Trento in Italy snipped bees’ right or left antennae and then paired off the clipped bees in petri dishes. When both members of the pair came from one hive, couples with intact right antennae responded quickly with a French kiss of sorts: They used their tongues to sample each other’s fluids. But leftie hive-mates held back the friendly overtures, sometimes exposing their jaws or pointing stingers at each other.

In pairs of bees from two different colonies, the right-antennaed bees wasted no time in becoming aggressive. The lefties, however, took longer to respond to the strangers and rarely bothered to get upset.

The right and left sides of the bees’ brains perform different functions, Vallortigara says, making their brains more like humans’ than scientists had expected. The open question is whether a common genetic recipe leads to brain asymmetry across species, Vallortigara says.

Every six years, Earth spins faster and then slower

The world turns slightly faster and slower on a regular 5.9-year cycle, a new study suggests. Researchers also found small speed changes that happen at the same time as sudden alterations in Earth’s magnetic field.

The world’s rotation speed can change slightly, by up to milliseconds per day, because of shifts in winds or the movement of fluid in Earth’s interior. Scientists can measure how fast the Earth spins by observing distant objects in space and timing how long they take to come back into view — that is one day length.

The new study, published in the July 11 Nature, found trends in day length after subtracting the effect of weather, allowing researchers to home in on the effect of Earth’s fluid core.

Scientists have previously found hints of six-year oscillations in day length, which occur at the same time as larger, slower changes. But the new analysis revealed that the cycle is remarkably regular, with the maximum change in day length occurring once every 5.9 years. Using decades’ worth of data, the researchers found that the oscillations maintained this precise timing and strength for half a century. “That’s got to be saying something important,” says geophysicist Bruce Buffett of the University of California, Berkeley, who was not involved in the study. It’s too early to say exactly what causes the oscillations, he adds.

This regularity undercuts one hypothesis for the cause of the cycles: fluctuations in the sun’s energy, which are more variable, says study author Richard Holme of the University of Liverpool in England. Instead, the cycle must be caused by something inside the Earth.

Holme’s team also detected sudden, tiny increases and decreases in the Earth’s rotation speed that coincided with abrupt changes in the behavior of Earth’s magnetic field, known as geomagnetic “jerks.” The new day-length data could help scientists understand what causes the mysterious jerks, Buffett says.

Along with hinting at what’s going on in Earth’s core, the research may help improve geomagnetic forecasts, which are crucial in mining exploration and drilling.