A comprehensive review of long‐distance hover fly migration (Diptera: Syrphidae)

Abstract Hover flies (Diptera: Syrphidae) are a group of insects containing many migratory species that provide critical ecosystem services including pollination, decomposition and biological control. Their migratory behaviour remains largely overlooked and unacknowledged, but an influx of contemporary research is beginning to shift this. The goal of this review is to summarise and synthesise the past 150+ years of global hover fly migration research from over 50 papers in multiple languages. Here, we provide comprehensive evidence for hover fly migration through the lens of the methodologies used for studying these phenomena, the biological mechanisms for migration and the associated ecological and economic impacts. We also include an inventory of all recognised migratory species and discuss taxonomic patterns. In total, we compiled accounts of 46 species that are considered migratory, most of which were sourced from Europe. Recent reports, however, have also described hover fly migration in North America, Asia, the Middle East and Australia. Approximately 70% of these species are from the subfamily Syrphinae, which are important biological control agents. The migratory behaviour of hover flies has substantial impacts on ecosystem services and may be linked to long‐distance gene flow for many angiosperms via pollen transportation. These insects are also likely redistributing biological control services at a continental scale on an annual basis, which has major repercussions for the management of crop pests such as aphids. The sensitivity of hover fly migration to anthropogenic impacts is not well known, but shifting climatic conditions, pollution and increased habitat fragmentation are likely impactful and should be further explored. Despite recent advances and increased interest in the subject, hover fly migration remains understudied and many major knowledge gaps continue to persist.