Hoverflies use a time-compensated sun compass to orientate during autumn migration

Area of Science:

• Animal behavior
• Insect migration
• Sensory ecology

Background:

• Daytime migratory insects are thought to use a time-compensated sun compass for orientation.
• Navigational mechanisms in migratory hoverflies (Diptera: Syrphidae) remain largely unknown.
• Hoverflies are abundant diurnal migrants crucial for ecosystem services.

Purpose of the Study:

• To investigate the navigational strategies of migratory hoverflies, specifically *Scaeva pyrastri* and *Scaeva selenitica*.
• To determine if hoverflies utilize a time-compensated sun compass during their autumn migration.

Main Methods:

• A flight simulator was employed to assess hoverfly orientation responses to celestial cues.
• Orientation of *Scaeva pyrastri* and *Scaeva selenitica* was measured during simulated autumn migration.
• The effect of circadian clock advancement on orientation was examined.

Main Results:

• Hoverflies demonstrated southward orientation when the sun was visible.
• A 6-hour advance in circadian clocks caused a westward shift in orientation.
• These responses are consistent with the use of a time-compensated sun compass.

Conclusions:

• Hoverflies *Scaeva pyrastri* and *Scaeva selenitica* primarily use a time-compensated sun compass for migration.
• This navigational mechanism is crucial for directed seasonal movements of hoverflies.
• Findings align with field observations of hoverfly migration under sunny conditions.