Spotted Lantern Flies: A Biological Invasion

Ellie Davis and Ali Bauer

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You have probably seen Spotted Lanternflies flying all over Radnor. They are red and black bugs that don’t usually directly bother us. So what’s the big deal? We see many different types of bugs every day. Spotted Lanternflies, however, are an invasive species that do not belong in Southeastern Pennsylvania. Not only that, but they are also destroying our trees. That’s right, that harmless-looking bug that you saw this morning on your walk to school has been quickly intruding and devastating our local ecosystems. 

Spotted Lanternflies — or if you want to get specific, Lycorma Delicatula — are native to China, Bangladesh, and Vietnam.  How they got here, however, is a mystery. In 2014, the first Spotted Lanternfly was found in Pennsylvania, specifically Berks County. Their migration story is truly anybody’s guess, but it is suspected that a small group of Lanternflies in their early life-cycle nymph stage hitched a ride to Pennsylvania, hidden in the packaging of goods shipped from Southeast Asia. 

Because of the invasion, the southeastern region of PA has been quarantined. This effectively means that any businesses that are moving materials between quarantine zones are required to have a permit mandating that they will check for any unwanted hitchhikers before driving anywhere. Anyone traveling between quarantine zones is advised to do the same, and it is strictly forbidden, in accordance with Pennsylvania law, to move any firewood or yard debris to an area outside your county. So far, Spotted Lanternflies have only made it as far west as Dauphin County, but over the past few summer months, it is suspected that they have traveled much farther inland. In the past five years, they have also been spotted in New Jersey and as far south as Virginia. 

Like all invasive species, their population has experienced a dramatic increase due to their lack of natural predators in the United States. Similar native species, such as aphids or cicadas, are healthy additions to our ecosystem, because natural predators and limited food supplies put a cap on their population growth. But with no one higher up on the food chain and ample food supply, Spotted Lanternflies are free to lay as many eggs as they want, and they can lay a lot. No predators are likely to naturally develop, as we might hope. Behavioral studies have found that the Lanternflies are unpalatable to birds, and though insects such as spiders and wasps have eaten them once already dead, no insects actively hunt live ones. With no factors limiting their population growth, Spotted Lanterflies have been given free rein of the Pennsylvania woods, with no foreseeable barriers standing in their way. 

While Spotted Lanternflies aren’t directly harmful to humans, the impact that they have on the environment is severe; their primary victims are trees. As we know, trees give off much of the oxygen that we breathe. Trees also remove harmful carbon dioxide from the atmosphere that would otherwise contribute to climate change. The Lanternflies use their straw-like mouths to suck up sap from trees, causing them to wilt and die. As they extract sap, they produce a sugary substance known as honeydew, which isn’t uncommon for insects. An excess of honeydew, however, encourages the growth of black, sooty mold, which further damages plants. In some cases, residents report rain appearing to fall from their trees, due to the mass amounts of honeydew. Similarly, residents have reported decks and other structures being entirely covered in the black mold. Some insects, such as bees and yellow jackets, have taken advantage of the new supply of honeydew by using it as a food source. While this may seem harmless, any dramatic influence of a non-native species, even if it is helping certain species in our ecosystem, will lead to disturbance. 

Along with environmental consequences, Spotted Lanternflies also negatively affect the economy. In Pennsylvania alone, they are threatening a billion-dollar agriculture business, particularly the production of grapes, apple, hops, and hardwoods. 

We haven’t been able to assess the full extent of the damage yet since the trees have not had long enough exposure to the Spotted Lanternflies, but we can expect to soon experience the severity of the situation first hand. To make matters worse, Spotted Lanternflies lay egg masses in clusters of 30-50 eggs each, so their numbers are growing exponentially.

The Lanternflies hatch in the springtime as flightless nymphs. They hop around eating sap until they have gone through their fifth molting phase, after which they can spread their wings and fly. This usually happens between the third week of July, but Lanternflies can remain in the nymph stage until late October. Over the summer, especially on warm breezy days, they have the opportunity to spread to new territory. By now, who knows how far they have gotten. All their life-cycle stages are in preparation for the most important time of the year: mating season. Beginning as soon as the first Lanternflies reach adulthood, mating season occurs throughout the fall. Before winter, they will lay their eggs on any surface they can find: trees, cars, houses, or your patio. All the adult flies that have wreaked havoc this season, after laying their eggs — thirty to fifty for each — will die out as soon as the first winter frost comes. Their eggs, however, will live through winter and will hatch in spring to start the cycle all over again. 

Measuring only about one inch long as an adult, Spotted Lanternflies are larger than many other insects. On the outside, they showcase grey wings with black dots. When a fly spreads its wings (or when you squash it like the good environmentally conscious citizen that you are), its bright red underwings emerge —  a telltale sign that it is a Spotted Lanternfly. Their eggs, another important component to their identity and destructive capabilities, are laid in groups with a plaster-like coating, and can be found on virtually any structure available to them.

Because the invasion of Spotted Lanternflies is so recent, there has not been much time for the state to intervene. So far, the main goal is to research these intruders so that we might know more about them and how to stop them. The main obstacle is funding, as the Pennsylvania Department of Agriculture is not prepared to fight the ecological damage posed by a biological invasion of this scale. In regards to biological control, that is, bringing in a predator of the Lanternflies from Southeast Asia to fight the population, if it is decided that this drastic of an action is necessary, it will be more than a decade before the US Department of Agriculture would approve of it. Biological control might even lead to more problems, as it could either cause the Spotted Lanternfly population to become resistant to biological control, or it could allow yet another invasive species to thrive in the Pennsylvania woods. 

So far, the only biological control we have against them is us. So next time you see a Spotted Lanternfly, which will unfortunately probably be in the near future, fulfill your duty to the environment and smash it!