Urbanization and environmental variation drive phenological changes in the spotted lanternfly, <i>Lycorma delicatula</i> (Hemiptera: Fulgoridae)

Abstract The spotted lanternfly (Lycorma delicatula) invaded the USA in 2014. The population has grown into the millions and spread across multiple states, primarily in the north-east but extending into the midwest. We analysed nearly 20 000 records of spotted lanternflies from the citizen-science platform iNaturalist across all reported locations in the USA to explore spatiotemporal patterns of activity and abundance as the invasion progresses. Observations on iNaturalist are consistent with reports of rapid exponential growth in the early years of the invasion. However, in the oldest parts of the invasive range, abundance exhibits logarithmic growth suggestive of reaching carrying capacity in these regions. Since 2015, observed activity has shifted earlier each year and life-cycle stages have lengthened concurrent with a general northern expansion. Activity patterns were correlated with urbanization generally, and earlier activity was associated with higher temperatures in both urban and non-urban locations. Together, these findings suggest that urbanization, and the urban heat island in particular, could facilitate invasion into colder climates and beyond predictions based on current occupancy. Understanding how life-cycle timing is shifting as the invasion progresses, in addition to the environmental factors shaping these changes, underscores the importance of integrating evolutionary ecology into invasion forecasts.