With some home security software and a bit of ingenuity, researchers have developed an inexpensive device that will allow them to study insect behavior and activity in areas of the world where they are most diverse.
Insects are by far the largest group of organisms on the planet, and with species inhabiting every continent, including Antarctica, they are also ubiquitous. Yet compared to birds and mammals, scientists know very little about when most insects are awake and active, which is especially true of nocturnal species that fly beneath the shadowy veil of darkness.
“Most of what we know about insect behavior comes from daytime active species,” said Akito Kawahara, curator of the McGuire Center for Lepidoptera and Biodiversity at the Florida Museum of Natural History and co-author of a new study describing the device. “We study butterflies, bees and ants because we can see them, but there are hundreds of thousands of nocturnal insects, all of which have been nearly impossible to track so far.”
Knowing when organisms are most active is the basis for understanding their behaviors and circadian rhythms – patterns that determine when they forage for food, reproduce, pollinate flowers and more. Without this basic information about insects, it is more difficult to predict or determine how changes in the environment, such as increased light pollution, might affect them.
But the smaller the animal, the harder it is to track. Insects are generally too small to carry tracking devices that would tell biologists their movements. Instead, researchers must lure them with bait or lights, which paint only a partial picture of their activity.
“You might think a moth is nocturnal because it has only been seen at night, but that doesn’t mean it hasn’t come out during the day. just hasn’t been seen,” said lead author Yash Sondhi, who holds a Ph.D. student at Florida International University co-supervised by Kawahara. “We wanted to look beyond the standard nighttime or daytime categories which might be an oversimplification.”
For years, Kawahara tried to find a portable device that would allow him to track insects while working in the field with his collaborator Jesse Barber at Boise State University, sometimes even trying to outsource the work to companies in the hope that they could build it for him. But equipment sensitive enough to measure the delicate movements of the smallest moths while being durable enough to withstand harsh environments and remote locations without electricity or the internet has proven difficult to design.
So when Sondhi offered to try creating it himself, Kawahara was thrilled. “We had put the project aside, but Yash was able to come in and build the device we had always imagined,” he said.
Sondhi has put together a microcomputer, open-source motion tracking software, sensors, a camera, and all-important infrared lights that won’t disturb or confuse insects. He housed all of this in a wire cage that looks like a laundry basket, and the wearable locomotion activity monitor, called pLAM, was born.
It can be built for less than $100, a tiny fraction of lab technology that costs between $1,000 and $4,000.
After using pLAM to monitor insect activity in the lab to make sure the equipment was working properly, Sondhi and Kawahara tested it on a research trip to Costa Rica. They collected 15 species, placing between four and eight moths of each in the activity monitors.
Sondhi says one of the most interesting examples was a species of tiger moth. It is assumed that these poisonous, brightly colored butterflies come out exclusively during the day, since predators avoid them, and they can move about without fear of being eaten. However, data from activity monitors revealed that they are also active at dusk. After all, they have to escape other predators that come out after dark, like bats.
“It was so cool to see the different business models,” Sondhi said. “Not everything is as black and white as we think. Now we can predict and better understand what motivates insects to fly. The goal is to quantify when they are active and then associate them with their traits – for example, if a moth is a dull, tan color, does that mean it is strictly nocturnal?”
Kawahara is optimistic that the new device will help inform efforts to stave off the recent global trend of insect decline and extinction. “The basic data we need to understand the activity of small insects and other organisms is so limited,” he said. “We talk about the impact of light pollution, noise pollution and climate change on insects, but we don’t know anything about their impact on their activity because we have not been able to monitor insect activity. most species of insects. This device will allow us to collect this information.”
This year, Sondhi will use this new tool to continue her National Geographic-funded research into how butterflies respond to light pollution. He collected data on different light levels at several field sites in India. Now he can examine how light pollution could perturb moths, interfere with their natural circadian patterns and impact their activity.
The research has been published in Methods in ecology and evolution.
Funding for the study was provided by the Florida International University Graduate School, the National Science Foundation, a Tropical Conservation Grant from the Susan Levine Foundation, a Lewis Clark Exploration Grant from the American Philosophical Society, a National Geographic Explorer and the Centers for Disease Control, Southeast Center of Excellence on Vector-Borne Diseases.