Honey bees have developed a way to turn pollen particles into a viscoelastic pellet, allowing them to transport pollen efficiently, quickly and reliably to their hive, according to a new study.
The study also suggests that insects remove pollen from their bodies at speeds 2-10 times slower than their typical grooming speeds.
“Removing a pollen pellet is like pulling off a bandage. “
To collect and transport pollen, bees mix pollen particles with regurgitated nectar and form it into a pellet that clings to each of their hind legs. The bees then place the granules in a cell in the hive, carefully scraping them with their other legs.
The study, from the lab of David Hu, a professor in the School of Mechanical Engineering at the Georgia Institute of Technology, aimed to gain a better understanding of the mechanics of this process that could inspire new ways of making and manipulating soft materials.
The paper appears in the Journal of the Royal Society Interface.
“We measured the properties of viscoelastic materials in a pollen pellet,” says Marguerite Matherne, a recent PhD graduate in Mechanical Engineering from Georgia Tech who now teaches at Northeastern University. “We have found that the lozenges have a very long relaxation time, which means that they mostly stay in solid form during the transport process. This is good because it prevents the pellet from melting or falling apart due to vibrations during flight.
Matherne and her colleagues also tried to replicate the way honey bees remove the pellets from their hind legs in the lab. They built a device that scraped off the pollen pellets stuck on the bees’ legs.
The invention produced two discoveries. The first was that the honey bees were much more efficient at removing the pellet than the scraping device they had built (the device left a lot more pollen residue on the paw). They also found that slower withdrawal rates reduce the force and labor required to remove pellets under shear stress.
“If you pull it out slowly, you can avoid applying the excessive force needed to pull it out quickly,” says Hu, former Georgia Tech advisor to Matherne. “Removing a pollen pellet is like pulling off a bandage. “
There are two key elements to the efficiency of the bees that carry these pellets, says Matherne. First, the pellets are slimy, which allows them to stick to the hind legs. But, she says, bees also have a special structure on their legs called a corbicula. It is fringed with long curved hairs and is embedded in the pellet, allowing adhesion.
Additionally, honey bees can collect pollen particles of different shapes and sizes, while developing a way to transport them. This is different from other bee species, which only collect and transport specific types of pollen of similar size. They also use different transport techniques.
“Honey bees harvest flowers from miles and miles away,” Hu explains. “Pollen can change size by a factor of 10. They have to collect all these individual particles and bring them back to one place. And they have to take a dozen foraging trips every day, while keeping their bodies clean. They solve all of this thanks to this special method they have created to exploit the properties of the soft material of the pellet.
The research team believes that further studies could lead to new developments in the applications of medical patches or fasteners for soft materials.
“It’s kind of like smart sticky Velcro for soft materials,” Hu explains. “It could be a tether and he knows when you’re trying to take it off so you don’t have to use excessive force.”
Matherne suggests that it is also important to understand the process of pollination since 35% of the world’s agricultural production depends on pollinators.
“Bees are really important pollinators,” explains Matherne. “If we’re going to create a world where we can keep our pollinators, I think it’s important to understand exactly what they’re doing.”
Source: Georgia Tech