Migratory hoverflies orientate north during spring migration

Abstract

Migratory hoverflies are long-range migrants that, in the Northern Hemisphere, move seasonally to higher latitudes in the spring and lower latitudes in the autumn. The preferred migratory direction of hoverflies in the autumn has been the subject of radar and flight simulator studies, while spring migration has proved to be more difficult to characterize owing to a lack of ground observations. Consequently, the preferred migratory direction during spring has only been inferred from entomological radar studies and patterns of local abundance, and currently lacks ground confirmation. Here, during a springtime arrival of migratory insects onto the Isles of Scilly and mainland Cornwall, UK, we provide ground proof that spring hoverfly migrants have an innate northward preference. Captured migratory hoverflies displayed northward vanishing bearings when released under sunny conditions under both favourable wind and zero-wind conditions. In addition, and unlike autumn migrants, spring individuals were also able to orientate when the sun was obscured. Analysis of winds suggests an origin for insects arriving on the Isles of Scilly as being in western France. These findings of spring migration routes and preferred migration directions are likely to extend to the diverse set of insects found within the western European migratory assemblage.

Tens of thousands of migrating hoverflies found dead on a strandline in the South of France

“…Though, while it looks clear that there are cues that initiate flight of hoverflies in massive numbers, we cannot draw conclusions on the processes influencing flight direction and behaviour (but see Gao et al, 2020). Similarly, we can only postulate that they originated from the south and were moving northwards, as is usually the case in spring migration (Hawkes, Weston, et al, 2022) and considering the wind direction during the days before the findings (Appendix ).…”

The genome sequence of a hoverfly, Syrphus vitripennis (Meigen, 1822)

“…This species is highly migratory, moving seasonally to higher latitudes in the spring and lower latitudes in autumn. They have been observed in June on the Isles of Scilly and in mainland Cornwall migrating northwards into the rest of Britain ( Hawkes et al , 2022 ). This species is common and widely distributed in Britain and Ireland, occurring in wide range of lowland habitats including woodland, clearings, gardens, parks and hedgerows.…”

The genome sequence of the Vagrant Hoverfly, Eupeodes corollae (Fabricius, 1794)

“…The species is found across Europe, Asia, and North Africa and, as the common name suggests, is a long-distance migrant. During the springtime, the hoverfly has been documented flying at least 105 km across open ocean from the Middle East to Cyprus ( Hawkes et al , 2022 ), and has been recorded heading south in the autumn through the Alps and the Pyrenees ( Aubert et al, 1976 ; Williams et al , 1956 ). In addition, entomological radar studies above southern Britain have confirmed seasonally directed movements, revealed their huge abundance and investigated their responses to wind currents ( Gao et al , 2020 ; Wotton et al , 2019 ).…”