Insights into natal origins of migratory Nearctic hover flies (Diptera: Syrphidae): New evidence from stable isotope (δ2H) assignment analyses

Hover flies (Diptera: Syrphidae) are an important group of insects that provide a multitude of key ecosystem services including pollination and biological control, yet many of their major life history traits are not understood. Some Palearctic hover fly species are known to migrate in response to changing seasonal conditions, yet this behavior is almost entirely unrecognized in Nearctic species. At least one species, Eupeodes americanus (Wiedemann 1830), is partially migratory during autumn while Allograpta obliqua may be non-migratory, but it is unknown where these insects originate and how far they may travel. We examined natal origins of two Nearctic hover fly species, Allograpta obliqua and Eupeodes americanus, using stable hydrogen isotope (δ2H) measurements of metabolically inactive tissues (wings and legs) to derive a hover fly δ2H isoscape. While Allograpta obliqua was mostly of local origin, several Eupeodes americanus were sourced from northern latitudes in the Midwestern Unit...