Spotted lanternflies—these invasive insects that first appeared in the United States a decade ago—are starting to come out earlier and remain active later in the year. This observation comes from a study analyzing citizen-science data by researchers from New York University. The extended lifespan and changes in their activity patterns may be partly influenced by the warmer climates found in urban areas.
Natively from certain regions in Asia, spotted lanternflies were first discovered in the US in 2014 in eastern Pennsylvania. Since then, their population has expanded throughout the Northeast, moving into the Midwest and Southeast, raising alarms about their potential damage to local flora and agriculture.
These colorful yet damaging pests became common in New York City starting in 2020—a fact not surprising to Kristin Winchell, an assistant professor of biology at NYU, who researches urban ecology and evolution. Cities frequently harbor invasive species for various reasons, including climate conditions, trade activities, and competition among species.
“Urban areas usually experience milder winters, which create ideal environments for species that typically thrive in warmer, tropical climates,” Winchell noted. “Moreover, cities serve as hubs for trade, allowing organisms to hitch rides on shipments transported via planes or boats between urban centers.”
“Lastly, urban environments often disadvantage many native species, resulting in a deteriorated ecological community that opens doors for new invasive species,” added Winchell.
After joining NYU in 2022—when spotted lanternflies were prevalent in New York City—Winchell and her colleagues became intrigued by how these insects were spreading across the US and whether urbanization played a significant role in their invasion.
Utilizing Citizen Science
Spotted lanternflies can be easily spotted due to their unique markings, which led to the public quickly learning to identify and report sightings to state authorities and citizen science platforms. One platform, iNaturalist, became a valuable resource for Winchell’s research team, particularly for Hannah Owen, an undergraduate who led this study after working in Winchell’s lab in New York City.
Owen examined nearly 20,000 photos of spotted lanternflies captured by citizen scientists in the northeastern US on iNaturalist from 2014 to 2022. She documented the insects’ locations and life stages to analyze population trends and activity patterns. The data collected on iNaturalist reflected a significant increase in lanternfly populations in northeastern states during the early stages of their invasion.
Along with Winchell and Fallon Meng, a PhD student studying spotted lanternflies, Owen found that both nymphs and adults were appearing earlier each year and remaining active for longer periods. This change in their lifecycle and activity timeline coincided with their northward expansion.
“This is crucial because a lengthened active period each year allows them more chances to reproduce and disperse,” Winchell explained.
By analyzing regional temperatures and various urban metrics—such as proximity to city centers, tree canopy coverage, and the extent of impervious surfaces—the researchers discovered a connection between increased temperatures and urbanization with the earlier emergence of lanternflies. This indicates that the warmer urban climates, often referred to as the urban heat island effect, may be aiding the creatures’ invasion into traditionally cooler areas.
The research team hopes their findings—published in the Biological Journal of the Linnean Society—will contribute to monitoring and controlling efforts for spotted lanternflies and other invasive species, especially in urban settings.
“If cities heighten their awareness, these major population hubs can take effective actions to manage invasive species,” Owen stated.
“As spotted lanternflies begin to appear earlier each year, cities could evolve into primary detection zones,” Meng added. “By focusing routine surveys on urban areas, we could provide early alerts to new territories and enable faster responses to curb their spread.”
Have New York City’s Spotted Lanternflies Reached Their Peak?
In regions where lanternfly invasions began earlier, like Pennsylvania and New Jersey, populations skyrocketed at first but have shown declines after four or five years, according to citizen-science data. While lanternflies can still be spotted in these states, they are no longer as numerous as they were in prior years.
“This kind of growth pattern is common with invasive species as they integrate into the ecosystem,” Winchell remarked. “It stands to reason that ecological limitations start to diminish the population—native species such as spiders, wasps, and birds are adapting to prey on lanternflies.”
The iNaturalist data indicated New York had the highest lanternfly population in 2022. Based on trends observed in states that had earlier invasions, the researchers anticipated that New York’s population would also peak and then start to decline in subsequent years—a prediction that has borne out this year, with significantly fewer sightings.
Given these patterns across states, Winchell suspects that the observed changes in population dynamics are more likely due to natural ecological processes rather than our individual control efforts. With smaller but stable populations in areas that peaked earlier, it suggests that these insects are here to stay.
“Will they swarm like they did a few years back? Probably not,” she concluded. “But are they disappearing? Not at all.”
