Tracking a Deadly Rise, Historic Fall of Insect Populations

An estimated 10 quintillion insects are alive on the planet, a staggering number that is at the center of a data crisis for entomologists. Researchers are struggling to understand historic shifts taking place among insect populations amid climate change and other environmental threats, from deforestation to pesticide use.

Nearly 40% of all insect species are declining globally while a third of them are now considered endangered. And yet, some deadly populations are on the rise.

Associate Professor of Physics Benjamin Thomas is developing new laser-based instruments to better study what is occurring among the world’s most diverse animal population, which accounts for roughly half of Earth’s animal biomass today.

“Because of their size and great diversity, it’s been difficult to collect data on insect populations to the point that entomologists talk about a data crisis in their field,” said Thomas. “Population trends we do have show great variance between insect families or groups and regions. For example, terrestrial insects seem to be more at risk of joining this insect decline than freshwater insects, which are increasing in some cases as climate conditions grow warmer and wetter.

“We are developing optical sensors to monitor our environment and provide better data to understand the situation. The goal is a diagnostic tool that can be widely deployed for surveying insect populations autonomously.”

With funding from the National Institutes of Health, Thomas has been establishing such a tool to track Earth’s most dangerous animal, responsible for over a half a million human deaths each year — mosquitoes.

For nearly five years, Thomas has been collaborating with the Hudson Regional Health Commission’s mosquito control program in Secaucus, NJ, where he is deploying his sensors.

His approach employs a scanning technology found in newer smartphones, LiDAR, which involves a laser wavelength in the near-infrared spectral range that is invisible to insects.

“We are sending a laser beam across open fields more than 50 meters, about 2 inches in diameter and about a foot above the ground. … When insects fly through the beam, our optical receiver measures the backscattered light,” explained Thomas. “By studying those optical signals, we retrieve a lot of information on any insect entering the beam, such as its wingbeat frequency, wing and body size, unique wing movements and more.”

Thomas says his instruments have registered more than a million insect observations last mosquito season, from April to October.

These observations could help Hudson County health officials track the abundance of deadly populations such as the mosquito species Culex, for example, which brought West Nile Virus to Queens, NY nearly 20 years ago and is growing in the New York City-Metropolitan region today.

Specifically, Thomas is tracking unique light signatures produced by females, which unlike males, can transmit disease using mouthparts capable of puncturing human skin.

“Females average 350 wing beats per second, compared to males at 500 a second,” said Thomas. “The instrument has a temporal resolution down to the minute so not only can we track population density over the season and potentially over years, but we can look at the behavior and peak of activities of groups each day.”

“While still being developed, I believe this technology will offer several advantages over traditional methods of adult mosquito surveillance,” said Gregory Williams, Superintendent of Mosquito Control at Hudson Regional Health Commission. “It will reduce the turnaround time for gathering data from the field, allow us to track the impact of our insecticides on non-target species and eliminate the sampling biases inherent in our current mosquito traps. … Even now, the current systems could be an excellent early-detection tool for invasive species or for monitoring specific disease vector species.”

Beyond tracking mosquito populations, Thomas says his research may give scientists much-needed data insights into insects in rapid decline, such as bees and other pollinators.

“What we do with mosquitoes can be done with pollinators, though it’ll take more instruments and continuous effort,” said Thomas. “We can identify them using a machine learning classifier we’ve been refining since we began working with mosquitoes … we first collect species data in the lab to train our models, allowing us to then identify and track activity of these insects in the wild.”

The work could be of significance to preserving vital agricultural landscapes — roughly 35% of the world’s food crops depend on pollinators to reproduce, according to the Food and Agriculture Organization of the United Nations.

Thomas plans to study pollinators locally in Secaucus and Newark, eventually scaling up to cover regions of rich wildlife such as New Jersey’s wetlands, to track how pollinator populations evolve over years.

“We started making measurements on species of wild bees in the lab already so we can more accurately identify them in the field,” said Thomas. “We think our observations can offer important new data on their peak of activity and behavior as it relates to weather and temperature, and hopefully, we can eventually begin to study things such as the impact of pesticide on pollinators, which may inform new strategies for protecting them.”