Adaptive strategies of high-flying migratory hoverflies in response to wind currents

Abstract

Large migrating insects, flying at high altitude, often exhibit complex behaviour. They frequently elect to fly on winds with directions quite different from the prevailing direction, and they show a degree of common orientation, both of which facilitate transport in seasonally beneficial directions. Much less is known about the migration behaviour of smaller (10–70 mg) insects. To address this issue, we used radar to examine the high-altitude flight of hoverflies (Diptera: Syrphidae), a group of day-active, medium-sized insects commonly migrating over the UK. We found that autumn migrants, which must move south, did indeed show migration timings and orientation responses that would take them in this direction, despite the unfavourability of the prevailing winds. Evidently, these hoverfly migrants must have a compass (probably a time-compensated solar mechanism), and a means of sensing the wind direction (which may be determined with sufficient accuracy at ground level, before take-off). By contrast, hoverflies arriving in the UK in spring showed weaker orientation tendencies, and did not correct for wind drift away from their seasonally adaptive direction (northwards). However, the spring migrants necessarily come from the south (on warm southerly winds), so we surmise that complex orientation behaviour may not be so crucial for the spring movements.

The long-distance flight behavior ofDrosophilasuggests a general model for wind-assisted dispersal in insects

“…The constant trajectory strategy has been observed in bumblebees, which actively compensate for wind drift during their nest-bound flights (19), and partial compensation has been observed in migratory noctuid moths (20). The constant heading hypothesis is consistent with radar observations of hoverflies' autumn migrations (21), and with laboratory experiments showing that tethered flies will maintain a fixed orientation relative to patterns of polarized light (22)(23)(24) or a small bright spot simulating the sun (25). Furthermore, these lab experiments indicate that each fly appears to choose an arbitrary heading from random that it then maintains over time, which could easily explain why the flies fanned out in different directions upon release.…”

Influence of weather on dragonfly migration and flight behaviour along the Baltic coast

“…There is a growing body of evidence for seasonally directed autumn migratory movements in large and medium-sized insects, including day-flying species (Srygley and Dudley 2008;Chapman et al 2015;Hu et al 2016;Knight et al 2019;Wotton et al 2019;Gao et al 2020). In dragonflies, directional autumn movements towards the south have been shown for long distance migrant species such as Anax junius (Wikelski et al 2006;Knight et al 2019).…”

“…Given the predominant southerly flight direction of A. mixta revealed in our orientation tests, this pattern might be indicative of the ability to select favourable tailwinds, which would facilitate migration. Many migratory insects such as dragonflies, moths and hoverflies, have been shown to select for favourable winds, possibly as an adaptation to maximize distance covered, optimize trajectories and reduce energy costs in their displacements (Anderson 2009;Alerstam et al, 2011;Becciu et al 2019;Knight et al 2019;Gao et al 2020). Across the study period, the prevailing winds from the SW and W -coming from the Baltic sea -were the strongest and most frequent, while the less common winds coming from the east were of lower speed.…”

“…Migration has evolved independently in a multitude of taxa within many of the major animal lineages (Alerstam et al 2003;Dingle and Drake 2007;Bauer and Hoye 2014;Dingle 2014). Insects are the most abundant and diverse group of terrestrial migrants (Holland et al 2006;Dingle and Drake 2007;Chapman et al 2015;Hu et al 2016;Satterfield et al 2020), yet migratory behaviour has only been well studied in relatively few insect taxa, often restricted to iconic species, such as the Monarch butterfly, Danaus plexippus (Flockhart et al 2013) or agricultural pests (Johnson 1969;Drake and Reynolds 2012;Chapman et al 2015;Jones et al 2019) and beneficial species (Wotton et al 2019;Gao et al 2020). Over the last 50 years, new tools have been developed to study insect migration at a higher resolution, for example using vertical-looking radars (Chapman et al 2003(Chapman et al , 2011aDrake and Reynolds 2012), and radio-telemetry (Wikelski et al 2006;Knight et al 2019).…”

Distribution of wild bee (Hymenoptera: Anthophila) and hoverfly (Diptera: Syrphidae) communities within farms undergoing ecological transition

“…The widespread distribution of syrphids in temperate landscapes and the availability of excellent taxonomic keys for European species identification are also characteristics that promote syrphids as bio-indicators. Syrphids are very interesting organisms for studying the effects of agriculture intensification on biodiversity because they are particularly mobile ( Gao et al 2020 ). Moreover, hoverfly communities are strongly affected by the standardisation in landscape structures and by intensive agricultural practices ( Dormann et al 2007 ).…”