Hoverflies use the sun and their body clock to help them navigate when they fly south for the winter, new research shows.
In the mornings the insects keep the sun on their left, and then gradually adjust to maintain a southward route as the day goes on.
In summer, pied and yellow-clubbed hoverflies – which are important pollinators – can be found in locations such as the UK and Scandinavia.
In the autumn they fly to the Mediterranean and north Africa.
While the migrations are known to happen on sunny days, researchers say the new study is the first proof of a time-compensated sun compass in the hoverflies.
Lead author Richard Massy, of the Centre for Ecology and Conservation on Exeter’s Penryn Campus in Cornwall, said: “Simply flying towards the sun would lead them south, but this would create a winding, inefficient route.
“Our study shows that hoverflies account for the sun’s movement using their circadian rhythm.
“Other animals, including certain birds and butterflies, are known to have this ability. Our work suggests that it has independently evolved across multiple insects.”
The insects were caught at a mountain pass in the Pyrenees, and placed into a flight simulator, which held them in place but allowed them to swivel freely.
They could see the sun, but not the ground, meaning they could not navigate using landmarks.
Researchers found that the creatures headed south by adjusting their course based on the sun’s position and the time of day.
Some hoverflies were placed in an artificial lighting environment for several days to shift their body clocks, and then their navigation was tested.
With their circadian rhythm disrupted, the direction of flight shifted westward – supporting the conclusion that they navigate using a time-compensated sun compass.
Dr Karl Wotton, of the University of Exeter, said: “Understanding how these insects navigate can help us predict their movements.
“This could be useful for conservation measures, such as limiting the use of pesticides at key migration times.
“Hoverflies are also important predators of crop pests such as aphids, so understanding their migrations could help us use them as natural pest controllers.”
The research, published in the journal Proceedings of the Royal Society B, was conducted by the University of Bristol, and funded by the Royal Society and the Natural Environment Research Council’s GW4 Doctoral Training Programme.