Several hundred bees in rural Pennsylvania and rural New York are sporting tiny QR codes on their backs.
More than the latest in apiarian fashion, the little tags serve a scientific purpose: tracking when bees go in and out of their hives to understand better how long honeybees spend foraging for food outside of their hives.
The work, a collaboration among entomologists and electrical engineers at Penn State, is the first step in solving a long-standing mystery of how far bees travel from their hives to collect pollen and nectar.
So far, the researchers have learned that while most trips outside the hive last mere minutes, a small minority of bees can spend more than two hours away. The team said they expect to learn much more, thanks to the system they developed to track honeybees’ time out of the hive.
"This technology is opening up opportunities for biologists to study systems in ways that weren't previously possible, especially about organic beekeeping," said Margarita López-Uribe, the Lorenzo L. Langstroth Early Career Professor, Associate Professor of entomology and author of the paper published in HardwareX.
"In field biology, we usually just look at things with our eyes, but the number of observations we can make as humans will never scale up to what a machine can do."
Like workers at a high-security building, the bees "buzz" their way in and out of the hive, flashing the pass on their back. They have free access, but they are digitally tracked via an automated imaging system the team developed to monitor when bees leave the hive and return via a customised entrance
with a camera sensor.
The QR codes glued to bees' backs are known as fiduciary tags, which carry the smallest amount of identification information and can be quickly detected and logged via the imaging system, even in low-resolution conditions.
The system is a break with conventional entomology fieldwork in which researchers visually observe bees for limited periods, enabling far more comprehensive and expanded observations, the researchers said.
Barriers to organic beekeeping
In general, organic beekeeping means that hives are kept free of chemical pesticides, herbicides and synthetic chemical treatments, and are situated away from polluted areas.
While the US Department of Agriculture's National Organic Standards Board recommended specific standards for certifying honey and other bee products as "organic" in 2010, they were never passed.
Honeybees are capable of flying long distances when they need to – estimated to be able to fly up to 10km from their hive – but the team hypothesised that such distance is uncommon and bees generally fly much shorter distances, perhaps less than 1km, according to López-Uribe.
As such, the forage and surveillance zone requirements recommended for organic beekeeping in 2010 may be unnecessarily large.
That could change with a better, more precise understanding of bee foraging range, the researchers said. Honeybees communicate where the food sources are to other bees in the colony with a physical behaviour called the "waggle dance".
López-Uribe said researchers spend significant time observing and attempting to decode the waggle dance to determine how far bees travel from their colonies – a process that could be aided by accurately tracking how long individual bees spend foraging.
"The waggle dance is
the best source of information that we have about bee foraging, but that's based on human observations, with maybe an hour of observations made once a day over two weeks.
“So, we approached the electrical engineering team to see if there might be technology that could better make these observations," López-Uribe said.
"The goal is to understand if that 10KM estimation is biologically accurate. Can we determine exactly how far honeybees travel from their hives?"
Buddying up for the bees
The entomologists turned to Julio Urbina, professor of electrical engineering and co-corresponding author on the study, who tapped Diego Penaloza-Aponte, a doctoral student in electrical engineering and co-corresponding author on the study.
"There wasn't anything available like this before," Urbina said. "This paper is the first step moving forward in the right direction, with opportunities to do more – in large part because of the growing synergy across our teams."
The researchers emphasised that this was not a collaboration of silos, where biologists and engineers pieced together separate contributions. Rather, the experts spent time as novices in each other's disciplines to better understand the specific needs and limitations.
The electrical engineers worked in the field, learning first-hand how to handle and monitor bees, while the entomologists visited the lab to learn what considerations go into designing and building automated technology.
"Systems built in the past to monitor bees were developed to run in or near controlled laboratory environments," Penaloza-Aponte said. "
Our goal was to develop something that could run in a rural environment, away from the lab, on solar power and to make everything open source. Anyone can use
this system and modify it."
According to Penaloza-Aponte, access was also of concern. All of the equipment used is commercially available and cost less than $1,500 in total per apiary, which includes six colonies.
Buzzing with new knowledge
The researchers used AprilTags, a QR code smaller than a person's pinky nail that could be glued to the worker bee without impeding her movement or causing harm.
Every two weeks throughout the active spring and summer season, the team tagged 600 young bees that had just emerged from their cells across six colonies. In total, they tagged over 32,000 bees across six apiaries.
"We targeted young bees so we could track their age more accurately, especially when they start to fly and when they stop," said Robyn Underwood, Penn State Extension educator in apiculture and co-author on the paper. She explained that young bees are also softer and don't sting yet, so they're easier to handle.
"Once the bee was old enough to fly, it would leave the colony and be seen under the camera. In real time, our sensor would read the QR code and capture the bee ID, date, time, direction of movement – leaving or entering the hive – and the temperature.
“Throughout the season, we could track individual bees. When did she leave? When did she come back? What was she up to?"
The researchers found that most trips typically lasted one to four minutes, which could be to check the weather prior to foraging or to defecate outside of the hive.
Longer trips typically lasted less than 20 minutes, but 34 percent of the tagged bees
spent more than two hours away from the hive. This could reflect an unusually long foraging trip, a bee who never returned to the hive or a missed detection if the bee entered the hive upside down, the researchers said.
During some weeks, with fewer flowers available, more bees spent more time foraging, likely because they had to travel farther to find adequate food.
"We also found that bees are foraging for a lot longer over their lifetimes than initially thought," said Underwood, explaining that honeybees are believed to live for about 28 days.
"We're seeing bees foraging for six weeks, and they don't start foraging until they are already about two weeks old, so they live a lot longer than we thought."
The cameras at each hive, running 24 hours a day and seven days a week, were each connected to a microcomputer, and the researchers uploaded the data to their laptops at weekly visits.
The researchers encountered an expected issue early in the monitoring – bees loitering in the hive entrance. The camera would detect their individual QR codes upwards of hundreds of times in a day.
"Turns out, some bees just like hanging out in the entrance, and the camera will read them every time they walk by," Diego said.
"That's why the programming is so handy. It can cut that outlier data and help make sure we're tracking what's actually meaningful."
Waggling into the future
The researchers are now collaborating with a team at Virginia Tech to assess how foraging duration times match decoded waggle dances.
Next, the researchers said they hope to tag and track other bee species, as well as other types of honeybees, such as drone bees or queen bees to learn more about those aspects of the colony.
They also plan to host workshops for scientists and beekeepers to learn how to build and use their own monitoring systems.