How moths and butterflies balance during flight and while hovering to collect nectar has long puzzled researchers. According to a U.S. team, the secret may be in their antennae
Credit: Armin Hinterwirth/University of Washington
SYDNEY: By severing moths' antennae then supergluing them back together, U.S. scientists may have cracked the mystery of how these insects balance during flight.
Over millions of years of evolution, some flying insects like flies, bees and wasps have lost one of the two sets of wings possessed by dragonflies, beetles, and butterflies, among others. The remaining vestigal stumps of these wings have evolved into balance organs called halteres that keep the insects steady during flight.
How moths and their relatives who retain four wings manage to balance without halteres has long puzzled researchers - especially their ability to hover when collecting nectar from flowers.
Published today in the U.S. journal Science, a study by a team of researchers from the University of Washington, Seattle, suggests that moths use their antennae like gyroscopes to balance without the halteres.
According to lead author Sanjay Sane, previous research on the antennae had focused more on their role in receiving olfactory, or smell, inputs. Studies aimed at understanding how moths maintain balance during flight, he said, had not focussed on the antennae in the same way his research did.
"We had a notion this would work, but everything before this had been anecdotal … I think these are the first data for this [mechanism]," said Sane.
Sane's team tested their ideas on hawk moths, a group of about 1,200 species of moths in order Lepidoptera - the same order as butterflies.
Their research showed that during flight, the moths' antennae moved in response to forces created by acceleration or side to side movements. Clusters of bristly hairs called Johnston's organs around the base of the antennae sensed these movements and passed them along to a specific, but enigmatic, area in the brain.
"We know that [the signal] goes into the brain, and that part of the brain is connected to the motor sensor - to the wing muscles, but what it exactly does, we do not know," said Sane.
To confirm that the Johnston's organs controlled balance by sensing the movements of the antennae, the team removed the ends of antennae from some moths. These moths lost all sense of balance and direction, flying randomly around the test room, sometimes crashing into the walls or the ground.
When the antennae were re-attached with superglue, the moths regained the majority of their in-flight agility. Sane thinks this research may open up a whole new angle in the study of antennae.
"From an evolutionary perspective this is a very interesting idea that somebody had a long time ago - that antenna are not all for olfactory reasons," he said. "Antennae are used to smell but the reason there are different shapes and forms may not be just for olfactory reasons."
