A pied hoverfly. Credit: Will Hawkes
New research has shown that hoverflies use the sun and their bodies clocks to navigate south during the winter.
In the morning, the insects keep the sun to their left. As the day progresses, they gradually shift to a southerly route.
The hoverflies, which are important pollinators, spend their summers in the UK and Scandinavia. In autumn they fly to North Africa and the Mediterranean.
These migrations occur on sunny days. However, the University of Exeter's new study is the first to prove that hoverflies have a time-compensated sun compass.
Richard Massy, lead author of the Centre for Ecology and Conservation at Exeter's Penryn Campus in Cornwall, stated that simply flying toward the sun would take them south but would make for a winding and inefficient route.
"Our study shows hoverflies are responsible for the sun's movement by using their circadian rhythm.
This ability is also known in certain birds and butterflies. It appears to have evolved independently across multiple insects, as our research suggests.
Researchers captured migrating hoverflies at an alpine pass in the Pyrenees.
Researchers Rich Massy, Karl Wotton are in the field. Credit to Will Hawkes
The insects were placed inside a "flight simulator", which kept them in place, but allowed them to move freely.
The hoverflies were able to see the sun, but not the ground. They could not navigate with landmarks and their results indicated that they went south.
The hoverflies were then placed in artificial lighting for several days to change their body clocks. This allowed them to test their navigation.
Their circadian rhythm was disrupted and their flight direction changed to the west. This supports the conclusion that they use a sun-compensated time compass to navigate.
Dr. Karl Wotton from the University of Exeter said that understanding how insects navigate can help predict their movements.
"This could be useful in conservation measures such as limiting pesticide use at key migration times.
"Hoverflies are important predators of crop pests like aphids. Understanding their migration patterns could help us to use them as natural pest control agents."
The University of Bristol was part of the research team. Funding came from the Natural Environment Research Council's GW4 Doctoral Training Programme and the Royal Society.
The paper was published in Proceedings of the Royal Society B. It is entitled "Hoverflies use an time-compensated solar compass to orientate themselves during autumn migration."
Learn more Migratory hoverflies are 'key' to as many insect declines.
More information: Hoverflies use a time-compensated sun compass to orientate during autumn migration, Proceedings of the Royal Society B, rspb.royalsocietypublishing.or .1098/rspb.2021.1805 Journal information: Proceedings of the Royal Society B Hoverflies use a time-compensated sun compass to orientate during autumn migration,
