Regional stability and pest increase in high-flying insectmigrants over nine decades

Reports of serious and widespread insect declines have been a source ofconcern for years, but long-term changes in migratory insect communities—which areimportant components of large-scale ecosystem functioning—are still little understood.Most migratory insects fly at high altitudes, making quantitative investigation problem-atic. Aerial trapping is the oldest sampling method, and generally still the only one thatcan provide information on species identity and adequately sample the smaller species.However, aerial sampling is laborious, and thus sampling periods are usually not continu-ous and sampling sites are sparsely scattered worldwide. To address these issues, we inte-grated existing data obtained by sampling from aerial platforms (and some high-mountainnetting in East Asia) in a comprehensive analysis. We found that, between 1926 and 2017,the aerial density of high-flying migratory insects from samples taken about 200 m aboveEurope (eastern United Kingdom), North America (southern and central United States),and Asia (east-central China, India, and the Philippines), remained relatively stable over-all. Additionally, some key migratory agricultural pests have significantly increased overthis period, indicating that the non-pest portion of the aerial migrant community may havedeclined. Changes in the community structure of high-altitude migratory insects will beclosely associated with large-scale ecosystem changes. Thus, apart from continued long-term monitoring of agricultural insect pests and the development of diversified preventionand control methods, there is a need to protect the diversity of non-pest and beneficialmigratory insects.