The spotted lanternfly (Lycorma delicatula) is an invasive planthopper native to parts of China, Taiwan, and Vietnam. It was first detected in the United States in Berks County, Pennsylvania, in 2014 and has since spread rapidly across several eastern states. This insect poses a significant threat to agriculture and natural ecosystems.
Spotted lanternflies feed on the sap of over 70 different plant species, including economically important crops like grapevines, fruit trees, and various hardwoods. Their feeding weakens plants and can reduce crop yields. As they feed, they excrete a sugary liquid called honeydew, which promotes the growth of black sooty mold on plants and surfaces. This mold can hinder photosynthesis, further damaging plants, and also creates a sticky nuisance in affected areas.
The Diverse Diet of Bats
Bats exhibit a wide range of feeding habits, with many species being insectivorous, meaning they primarily consume insects. These nocturnal mammals are highly adapted for hunting in darkness. They utilize echolocation, a biological sonar system, to navigate and locate prey.
Bats emit high-frequency sounds and then interpret the echoes that return, allowing them to construct a detailed acoustic map of their surroundings. This system provides information about an insect’s size, shape, and movement, even in complete darkness. Many insectivorous bats capture their prey directly in mid-air using their wings or tail membranes. A single bat can consume thousands of small insects in one night due to their high energy demands from flying.
Investigating Bat Predation on Spotted Lanternflies
Recent scientific investigations have begun to explore whether bats prey on spotted lanternflies. Researchers have analyzed bat guano, or droppings, for the presence of insect DNA to identify what bats are eating. This method allows for the detection of specific prey items without directly observing feeding events.
Studies, including one from Rutgers University, have successfully detected spotted lanternfly DNA in the guano of native bat species, specifically big brown bats and eastern red bats. This finding confirms that these bats are indeed consuming spotted lanternflies. The detection rates of spotted lanternfly DNA in bat guano have shown an increase over time, correlating with the expansion and increasing abundance of the invasive insect.
While this research confirms bats prey on spotted lanternflies, it does not yet quantify the extent or impact on lanternfly populations. DNA presence indicates consumption, but not how many lanternflies a bat eats or how frequently. These findings suggest bats may opportunistically incorporate spotted lanternflies into their diet as the insects become more prevalent.
Factors Influencing Bat-Spotted Lanternfly Interactions
Several biological and ecological factors can influence the degree to which bats prey on spotted lanternflies. One consideration is the potential for chemical defenses in the lanternflies. Spotted lanternflies can sequester compounds from their host plants, which might make them unpalatable or toxic to some predators. However, the documented consumption by bats suggests that either these defenses are not universally effective against bats, or bats are consuming them despite such defenses.
Habitat overlap between bats and spotted lanternflies is another influencing factor. Bats often forage along forest edges, roadsides, and near water bodies, which are areas where spotted lanternflies tend to congregate. The activity times of both species also play a role; spotted lanternflies are primarily active during the day, while bats are nocturnal. However, adult spotted lanternflies are present during the fall, which overlaps with the active foraging periods of big brown bats and eastern red bats as they prepare for hibernation or migration.
Differences in foraging behavior among bat species can also affect their likelihood of consuming spotted lanternflies. Most insectivorous bats are aerial hawkers, catching flying insects in mid-air. While adult spotted lanternflies can fly, their primary mode of movement is often hopping or short-distance flight. Some bat species also engage in gleaning, which involves picking stationary prey from surfaces, potentially allowing them to target resting lanternflies. The larger size of adult spotted lanternflies compared to many other insects might also make them a more noticeable or energetically rewarding prey item for certain bat species.