Insect phenology has shifted in recent decades under global change, with implications for trophic interactions, ecosystem services and pest management. Shifts towards earlier phenology are well documented for emergence, reproduction, and length of activity period. However, global change effects on the timing of insect seasonal migration are unknown, as are their drivers.
We use a dataset of more than 25 years across 14 species in 3 orders (Hemiptera, Lepidoptera, Odonata ) to evaluate variation in migration phenology. We examine migrant arrival in the US Midwest, Great Plains and Northeast, from data collected by agricultural practitioners, scientists and community members. We identify shifts in insect migration phenology in the past 20 years, and how variation in local temperature drives long-term trends in arrival phenology.
The timing of migrant arrival has advanced across species and states in the Eastern United States. We find that smaller bodied insects show greater shifts in migration phenology. Species vary in the change in migration phenology, with earlier arrival in most Lepidopteran pests (e.g. Helicoverpa zea, Spodoptera frugiperda), while some Hemipteran species advance in their phenology (e.g. Myzus persicae) and others arrive later. Preliminary results indicate that advances in arrival timing are not correlated with changes in temperature, suggesting that insect migration may be driven by resource availability or atmospheric conditions favorable to dispersal rather than by temperature. By compiling data from a range of sources and taxa, this study demonstrates the complexity of migratory species responses to global change.
