Step one: Gently suck up the bumblebees with a special vacuum. Step two: Place them in the fridge to chill until they’re immobilized. Step three: Remove bees and superglue a sort of tiny, simplified QR code on their backs.
Superglue what, you say? Yes, QR codes—a pretty significant upgrade for entomologists. Researchers used to stand over colonies, laboriously tracking the behavior of individual bees. But with this system, called BEEtag, cameras can automatically monitor hundreds of bees all day and night, exposing their personalities and interactions. That is, after the bees warm up from their chilly nap.
In a study published Tuesday in the journal Nature Communications, a group from several universities looked at how worker bees—responsible for everything from feeding larvae to ventilating a hive—know when to switch jobs. Specifically, they wanted to know how a worker knows to jump in and collect food when a designated forager dies. But the technique can help understand lots of bee behaviors—including the abnormal kind that can result as populations are threatened by pesticide use.
Bombus impatiens bumblebees may look like automatons, but machine vision tracking those codes reveals that they’re actually chock-full of personality. “We found an enormous amount of individual variation in behavior,” says Harvard biologist James Crall, lead author of the paper. “So not just there being foragers and nurses per se, but even among foragers, certain foragers were foraging all the time and sort of continuously going on lots and lots of bouts throughout the day.”
Some individuals move around more in the nest. Some interact more with their nestmates. Some are just generally more active.
The question is: With no one giving explicit orders, which bumblebees get the dubious honor of volunteering their lives as foragers in the big bad world? “Insects societies are decentralized, they are the classic complex systems. The lights are on but nobody's home,” says Gene E. Robinson, director of the Carl R. Woese Institute for Genomic Biology, who was not involved in the study. “So no one is telling the workers what to do. There's no hierarchy, there's no chain of command.” So when a forager dies—or gets nabbed by a meddling researcher, in this case—something else must be determining which individuals take their place.
The researchers here looked at bee movement patterns around the colony, including the food storage area, where foragers deposit grub in “honey pots." (Adult bumbles eat nectar, by the way, while they feed their larvae pollen.) They found that different workers hang out in different parts of the nest, and every day they would revisit those same spots.
“Only where bees were seemed to predict who switches,” says Crall. “The bees that are interacting most with the food storage regions of the nest are the ones that get the best and the fastest information on, 'OK, it's time to go out and forage and take up that slack.'” Think of it like being the one who drinks the last bit of milk from the fridge—it’s your responsibility to go get more.
If the BEEtag system can help decode the complex goings-on of a bumblebee colony under siege by forager-snatching predators, it can also quantify what happens to a bumblebee colony under siege by humans. “Now what we're doing is exposing bees to known neuroactive pesticides and seeing if behavior within the nest is disrupted,” says Crall. Typically, researchers test a chemical’s effects by measuring LD50, or the dose that kills 50 percent of your sample. But that doesn’t take into consideration the complex social structure of the colony.
“It's really important to look at the social side,” says University of Bristol biologist Sam Duckerin, who uses the BEEtag system for his own work. “When you consider bumblebees, maybe the lethal dose is the same as in honeybees, but actually the colony is much more likely to be strongly affected when individual bees are being lost.” While honeybees can maintain populations in the tens of thousands, Bombus impatiens hives usually number around 200—so any loss is significant.
For the moment, the process of chilling bees and tagging them remains a bit tedious. But maybe soon pesticides will have to go through testing with BEEtag before regulatory approval. “That would be the hope,” says Duckerin, “that one day this sort of thing would be relatively easy to implement across big samples to actually be able to use these tests for all sorts of different chemicals.”
So how about that: QR codes have finally made themselves useful beyond selling you stuff.
-Bees are in trouble, but not the ones you're thinking.
-One scientist's crazy bet to save the bees by … joining Monsanto.
-Amid all the doom and gloom, let's take a moment to appreciate the relentless beauty of bees.
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