COVER PHOTO: Hover flies (Diptera: Syrphidae) provide a multitude of ecosystem services including pollination and biological control. In their paper in this issue, Clem et al. (Article e1542; doi:10.1002/ecm.1542) examine for evidence and mechanisms of long-distance migration in Nearctic hover flies. Using stable hydrogen isotopes (δ²H) combined with abundance, morphological, and cold-tolerance data, they found that North American species like Eupeodes americanus (pictured here in central Illinois, USA) migrate south during autumn in response to encroaching winter conditions. Hover fly migration likely has major implications for ecosystems including pollen and nutrient transfer, and provision of sustainable pest management. Photo credit: C. Scott Clem.

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封面照片：悬停苍蝇（双翅目：食蚜蝇科）提供多种生态系统服务，包括授粉和生物控制。在本期的论文中，Clem 等人。（文章 e1542；doi:10.1002/ecm.1542）检查近北极悬停苍蝇长距离迁移的证据和机制。使用稳定的氢同位素 (δ ² H) 结合丰度、形态和耐寒性数据，他们发现北美物种，如美洲桉（图为美国伊利诺伊州中部）在秋季向南迁移，以应对冬季的侵袭。悬停飞行迁移可能对生态系统产生重大影响，包括花粉和养分转移，以及提供可持续的害虫管理。图片来源：C. Scott Clem。