Flies on vacation: evidence for the migration of Australian Syrphidae (Diptera)

Abstract

1. Hover flies (Syrphidae: Diptera) are a cosmopolitan group of insects that provide important ecosystem services including pollination and pest control. The seasonal migration of hover flies is probably best known in Europe, but it remains unstudied in many other parts of the world.2. Australia is believed to be home to around 160 hover fly species, some of which are common in urban and agricultural environments. The current evidence for hover fly migration in Australia is scarce and anecdotal, yet migration may be critical to the success of pollination and the biological control of aphids.3. In this study, species occurrence records from an online biodiversity database (Atlas of Living Australia) were used to look for evidence of migratory behaviours in all Australian hover flies with more than 200 occurrence records.4. Four of the 10 species displayed seasonal changes in their distribution consistent with migration, including Australia's two most abundant species: Melangyna viridiceps and Simosyrphus grandicornis. This work is an important first step in understanding the prevalence of migration in Australian hover flies. However, confirmation of our findings requires additional evidence to rule out other plausible explanations for the observed patterns.5. Based on changes in summer and winter latitudinal distribution, it is estimated that some Australian hover flies may make annual migrations of 400–1800 km.6. This work suggests that the management of beneficial insects requires consideration of factors at both local and continental scales, as landscape use changes may have an impact on ecosystem services delivered hundreds of kilometres away.