Courtesy of Cornell University

May 3, 2023

Cornell Researcher Discovers Artificial Light Enhances Caterpillar Predation

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Using clay caterpillar replicas as bait for predators, Cornell graduate John Deitsch ’22 found that increased artificial light enhances caterpillar predation. 

Deitsch graduated from Cornell in 2022 with a double major in biological sciences and entomology, though his interest in the interaction between insects and artificial light extends back to high school. As a budding entomologist, he enjoyed watching moths interact with a lightbulb, and when considering a topic for his honors thesis, turned to his long-term interest in artificial light. 

To observe the relationship between artificial light and enhanced predation on insects, Deitsch and his team of researchers created over 550 caterpillar replicas out of soft modeling clay. These mimics were placed in eight separate pairs of plots — one that was experimentally illuminated and one that was naturally illuminated.

By examining the imprints made on the soft clay caterpillars by local predators, the Cornell researchers were able to observe the differing predation rates between the paired plots.

While the experimental design is an accepted method of studying predation, there are several limitations, according to Deitsch. 

“Some predators — and most parasitoids — simply don’t target artificial prey models and marks left by predators cannot be reliably identified at a fine taxonomic scale,” Deitsch wrote in a statement to The Sun. “Nevertheless, we found clay caterpillars a happier alternative to the struggle of mass-rearing and live-tethering genuine caterpillars.”

The research team found that predation on the clay caterpillars and abundance of arthropod predators and parasitoids were higher on the plots that were exposed to artificial light. The impact of artificial light on predator-prey relationships is an active area of research, according to Deitsch. However, these findings seem to point toward a trend in how arthropod communities react to artificial light exposure poses a potential ecological threat to caterpillar populations, as artificial lighting at night from homes and other buildings becomes more ubiquitous.

“One nice aspect of light pollution is that the negative impacts largely disappear when lights are turned off,” Deitsch said. “It doesn’t linger for days or decades or generations like plastics and chemicals. Turning off unnecessary nighttime lighting is an easy step to help reduce the impact of artificial light on insects and other organisms.”

Since conducting his honors thesis research, Deitsch has worked for the Georgia Department of Natural Resources and as a field technician through the University of Georgia. He will be starting graduate school at the University of Texas at El Paso in August where he plans to continue his research on light pollution and insects. 

“There’s just so many questions left to answer about artificial light and arthropods,” Deitsch said. “Insects and other arthropods already face so many other threats like habitat loss, widespread pesticide use and climate change. It’s important to know where light pollution fits into this puzzle.”

Anna Labiner is a staff writer. She can be reached at [email protected].