A simple rubbing technique borrowed from grade-school art class offers a quick and effective way for scientists to measure damage to trees caused by bark beetles—and an accessible tool for engaging the public in forest entomology. First, a log of an affected tree is debarked (A), wrapped in rice paper (B), and rubbed with a graphite pencil (C). Then the paper with the rubbing is unwrapped so it can be viewed flat. Researchers can then scan the rubbing into image-processing software to calculate total area of the tunnels, or “galleries,” created by bark beetle larva as they feed on the tree. They can also use the software to measure the length of individual or combined gallery segments and the locations of egg niches and nuptial chambers. (Image originally published in Palmer and Hartshorn 2025, Journal of Insect Science)

By Fabiana Fragoso, Ph.D.

Fabiana Fragoso, Ph.D.

From North America’s pine forests to Europe’s spruce stands, bark beetles (Curculionidae: Scolytinae) have been leaving their mark—quite literally—across vast landscapes. As they tunnel beneath the bark to feed and reproduce, these destructive borers carve intricate galleries that can kill whole trees and reshape entire forests. As some of the most destructive insect pests in the world, bark beetles have caused devastating timber losses, altered ecosystems, and heightened wildfire risk.

That’s why, for scientists and forest managers, finding better ways to measure bark beetle damage and predict outbreaks is essential. Traditional methods are often slow, labor-intensive, and prone to inconsistencies. Their cryptic life cycle makes monitoring difficult, and trap catches don’t always reflect the actual tree damage or mortality. Now, a study published in October in the Journal of Insect Science introduces a simple yet innovative method that makes the process faster and cheaper—and, intriguingly, more artistic.

A Sketch Beneath the Bark

Jess Hartshorn, Ph.D.

Bark beetle larvae develop hidden beneath the bark, where their galleries record their growth and feeding patterns. Quantifying those galleries is key to estimating population size and predicting outbreaks, but existing methods are few and painstakingly slow. When Jess Hartshorn, Ph.D., and her then lab manager J. Forest Palmer at Clemson University (Hartshorn is now an associate research professor of forestry at Central State University) were working on a U.S. Forest Service-funded project that required quantifying bark beetle development, they quickly realized it was no small task. “We started going through logs and using standard tools like rulers to measure gallery length, and we both just thought there had to be a quicker and easier way to do that,” Hartshorn says. “So we just sat down together and came up with a few options that we started running through. I guess the problem was my impatience,” she jokes, crediting her neurodivergent tendency to seek more efficient solutions for sparking the idea.

A simple rubbing technique borrowed from grade-school art class offers a quick and effective way for scientists to measure damage to trees caused by bark beetles—and an accessible tool for engaging the public in forest entomology. Here, a log wrapped in rice paper has been rubbed with graphite pencil, revealing the pattern of the bark-beetle galleries on the surface of the debarked wood. (Photo courtesy of Jess Hartshorn, Ph.D.)

Before settling on their rice-paper rubbing method, Hartshorn and Palmer experimented with a few alternative ideas. Hartshorn was excited with the possibility of coating logs with liquid latex to create a three-dimensional mold of the beetle galleries. “I was pretty sad when that didn’t work,” Hartshorn says. “The logistics were just too much. We would have had to build a mold for each log or a few logs, and the molds would only work for a handful of logs before they’d quit being effective, so we’d need to make a new one each time. Or we would need to do many coats of latex, waiting for it to cure between coats. Either way, it would have been too much to be efficient for what we needed.”

After several rounds of trial and error, the pair discovered the right mix of efficiency and precision. Their method involves placing a sheet of rice paper on the exposed beetle galleries, rubbing graphite gently over the surface, and then photographing the resulting image. The digital rubbings are analyzed in ImageJ, a freely available software, to calculate total gallery area, turning what had been a time-consuming process into a quick and inexpensive task. Beyond measuring gallery area, the researchers note that ImageJ plugins allow scientists to extract even more details, such as the length of individual or combined gallery segments and the locations of egg niches and nuptial chambers. The method offers new ways to study bark beetle behavior and development.

A simple rubbing technique borrowed from grade-school art class offers a quick and effective way for scientists to measure damage to trees caused by bark beetles—and an accessible tool for engaging the public in forest entomology. After creating a rubbing by wrapping a debarked log with rice paper and rubbing it with graphite pencil, the paper is laid flat, and reseachers then placed a transparency sheet over it, onto which they traced the gallery patterns in different colors according to the genus of beetle that created them. Here, green indicates Ips and red indicates Monochamus. (Photo courtesy of Jess Hartshorn, Ph.D.)

From Forest Health to Citizen Science

Beyond the novelty of the method itself, Hartshorn envisions practical benefits for both researchers and forest managers. “My hope is that, since we used readily available and inexpensive tools, managers could quickly fell a few trees, debark them, and use this method to look at development of bark beetles and their predators,” Hartshorn says. “Traditional trapping is not always indicative of actual populations and also involves specialized traps and lures, which are expensive and require specific storage. And then the insects need to be sorted and counted as well.”

By contrast, the rubbing method offers a low-cost, field-friendly alternative that could complement monitoring programs and perhaps even engage the public. “I think the application to citizen science could be fun, too,” she says. “People could even use this as a way to commemorate a loved tree that was taken out by beetles. It could definitely be used as an educational tool that also results in something fun that folks could keep for themselves afterwards.”

Where Art and Science Align

What makes this study stand out is not just its practicality but its creativity. Each rubbing captures the winding path of beetle galleries, producing images that for some might be as visually compelling as they are scientifically useful. “Silviculture is defined as the ‘art and science of controlling the growth, structure, and quality of trees and forests,’ so we already see the inherent value in art within forest science,” Hartshorn says. “Every scientist has had to rely on a bit of artistic creativity to develop methods, interpret data, et cetera. In the same way, artists know the ins and outs of their materials, how they interact together to create something different, and use scientific inquiry to come up with new ways of creating. I think science and art are two sides of the same coin, so I absolutely will keep exploring those connections throughout my career.”

Fabiana Fragoso, Ph.D., is an entomologist, biologist, translator, and interpreter native to Brazil and soon to be based in Italy. She most recently served as a postdoctoral researcher with the U.S. Department of Agriculture’s Agricultural Research Service in Madison, Wisconsin, USA. Email: [email protected].