Spotted lanternflies — invasive insects that first landed in the United States a decade ago — are emerging earlier and staying active later each year, according to an analysis of citizen-science data by researchers at New York University. This longer life cycle and shift in activity may be driven in part by cities and their warmer climates.
The spotted lanternfly, native to parts of Asia, was first found in the US in 2014 in eastern Pennsylvania. Since then, the population has spread across the Northeast and into the Midwest and Southeast, sparking concerns about its impact on local plants and agriculture.
The colorful but harmful insects became a common sight in New York City in 2020 — which wasn’t surprising to Kristin Winchell, an assistant professor of biology at NYU who studies ecology and evolution in urban environments. Cities are often home to invasive species for a number of reasons, including climate, commerce, and competition.
“Cities tend to have milder winters, creating favorable conditions for species that otherwise would only be able to live in hot, tropical climates,” explained Winchell. “Cities are also highly connected places where trade happens, and organisms may end up on shipments in planes or boats traveling between cities.”
“Finally, urban environments aren’t very friendly to a lot of native species, so you have a degraded ecological community that creates opportunities for new species to come in,” said Winchell.
Upon joining NYU in 2022 — a time when spotted lanternflies were abundant in New York City — Winchell and her team grew curious about the spread of lanternflies in the US and whether urbanization was playing a role in the invasion.
Harnessing the power of citizen science
Because spotted lanternflies are easy to identify, thanks to distinctive markings on their bodies and wings, the public quickly learned to recognize and report them to state governments and citizen science platforms. One such platform, iNaturalist, provided a rich source of data for Winchell’s research team, including Hannah Owen, who led this study as undergraduate at NYU Shanghai after spending a semester in Winchell’s lab in New York City.
Owen analyzed nearly 20,000 photos of spotted lanternflies in the northeastern US that citizen scientists uploaded to iNaturalist between 2014 and 2022, noting the locations and life stages of the insects to explore population patterns and activity. The patterns of lanternflies documented in iNaturalist were consistent with their rapid growth in northeastern states in the early years of the invasion.
Together with Winchell and Fallon Meng, a PhD student in Winchell’s lab studying spotted lanternflies, Owen noticed that lanternflies — both nymphs and adults — were showing up earlier each year and remaining active later. This shift in the timing of their activity and extended life cycle coincided with the insects spreading farther north.
“This is important because a lengthening of the active period every year means they have more time to reproduce and spread,” said Winchell.
Looking at regional temperature and several measures related to urban areas — distance to a city center, tree canopy cover, and paved surfaces and roofs — the researchers found that both higher temperatures and urbanization were linked to the lanternflies emerging earlier. This suggests that cities and their warmer temperatures — known as the urban heat island effect — may be facilitating the spread of spotted lanternflies further north into colder regions, including areas previously thought to be too cold for the insects to thrive.
The researchers hope that their findings — published in the Biological Journal of the Linnean Society — might inform monitoring and mitigation efforts for spotted lanternflies and other invasive species, particularly in cities.
“If cities are more aware, then these large population centers can do more to contain invasive species,” said Owen.
“With spotted lanternflies showing up earlier each year, cities could become early-detection zones,” said Meng. “If people focus on urban areas for routine surveys, this could provide early warnings to new regions and faster response times to potentially limit the spread.”
Have New York City’s spotted lanternflies peaked?
In areas where lanternfly invasions started earlier, such as Pennsylvania and New Jersey, the populations initially grew exponentially, but the citizen-science data showed them peaking and declining after four or five years. While spotted lanternflies are still found in these states, they are far less prevalent than they were several years ago.
“This is a classic growth pattern that we see in invasive species as they become part of the ecological community,” said Winchell. “It makes sense that ecological pressures start to knock down the population — for instance, native species like spiders, wasps, and birds are learning to prey on the lanternflies.”
The iNaturalist data showed New York having the largest lanternfly population in 2022, and based on patterns in states with earlier invasions, the researchers predicted that the population would peak and decline in the years that followed — a prediction that played out this year, with far less frequent sightings of the insects.
Because of these patterns across states, Winchell thinks it’s more likely to be a natural ecological process playing out — not our individual efforts to stomp on bugs — changing the population’s trajectory. And based on the smaller but sustained populations of spotted lanternflies in places that peaked earlier, it’s likely that these insects are here to stay.
“Will they swarm again like they did a couple of years ago. Probably not,” she said. “But are they going away? No.”
