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Caffeine Makes For Busy Bees, Not Productive Ones

A caffeinated bee is a busier bee. It’ll work harder to find food, and to communicate the location of said food to other bees. It will, however, misjudge the quality of the food it finds, and so make its colony less productive. The irony of writing about this as I sip an unwisely strong espresso at 10 pm is not lost on me.

The caffeine in coffee might give me a mental kick, but many plants rely on its bitter taste to deter plant-eating animals. Others, however, seem to bait themselves with caffeine, doping their nectar with low concentrations of the stuff. Why add a bitter deterrent to a liquid that’s meant to entice and attract pollinators?

Geraldine Wright from Newcastle University found one possible answer in 2013, when she showed that caffeine can improve a honeybee’s memory. Wright fed the insects with caffeine at concentrations that would affect their bodies, but that wouldn’t register as a bitter taste. She found that these bees were three times more likely to remember a floral scent. So, by providing caffeine, plants ensure that their pollinators are more likely to learn the link between their distinctive scents and the tasty nectar they provide.

What about the bees? Do they benefit from being drugged like this? One might think so, because they can more efficiently find the food they need. But Margaret Couvillon from the University of Sussex thinks otherwise.

She trained honeybees to forage from two feeders full of sugar water, one of which had been laced with a small amount of caffeine. She found that the caffeinated bees made more visits to the feeders. Once back in the hive, they were more likely to perform the distinctive waggle dance that tells other bees where to find food, and they performed the dance more frequently. And this means that a hive which exploits a caffeinated flower will send out about four times as many workers to that flower.

That wouldn’t be bad if this newly energised armada of workers was behaving more efficiently. But they’re not. Couvillon’s team showed that they’re more likely to persist with a caffeinated food source, even when that source no longer becomes useful. They also become faithful to their chosen feeder and become less likely to stray to a different host plant.

So, there’s the rub. Even though caffeine improves bee memory, it also causes them to overvalue caffeinated plants over decaffeinated ones that offer the same amount of energy. As the team writes, “The effects of caffeine in nectar are akin to drugging, where the pollinator’s perception of the forage quality is altered, which in turn changes its individual behaviours.”

By simulating these effects, Couvillon showed that if 40 percent of plants in the environment produce small amounts of caffeine—a realistic proportion—bee colonies would produce around 15 percent less honey every day.

They still need to test this prediction in real-world experiments. But if the results check out, it suggests that plants use caffeine as more than a deterrent against undesirable animals, but also as a way of manipulating desirable ones.

See amazing honeybees in “Hello, Honey! 10 Sweet Pictures of Bees.”

Tar Pits Bees Connect California’s Past to the Present

The La Brea asphalt seeps are practically synonymous with megafauna. Sculptures of American lions and scrapping Smilodon draw visitors into the on-site Page Museum, well-stocked with Ice Age celebrities that have been reconstituted from the mind-boggling number of bones found beneath Los Angeles. Even more bones are kept in rows upon rows of bins in the collections – perhaps the greatest fossil dataset in the world – but it would be a mistake to think that La Brea is all about sabercats and mammoths. The story of prehistoric California was like, and how the world has changed as the last Ice Age slipped away, is kept by a diversity of meeker creatures, including a pair of unborn leafcutter bees that may be the most intricate fossils ever to be pulled from La Brea.

In 1970, from a La Brea dig called Pit 91, excavators found a tiny little nub of plant material. Anywhere else this pill-shaped fossil might have been treated as an uninteresting bit of ancient scrap, but La Brea had made a policy to collect and catalog every scintilla of fossil material they found, down to beetle wings and plant pieces. The fossil was saved, curated, and was later found to be part of a prehistoric bee nest, but it was otherwise forgotten. The insects of La Brea haven’t received anywhere near the same scientific attention as the site’s large beasts.

That lack of interest from other researchers created an opportunity for entomologist Anna Holden, who wanted to know just what the Page Museum had in their insect stockpile. “I knew that I would find treasures going through the insect collections,” Holden says, and when she opened a small fossil labeled LACMRLP 388E, she immediately knew she had something special. “I got to this snap cap and said ‘Oh my god, these are leafcutters.'”

The fossil itself wasn’t an adult, petrified bee, but rather a leafcutter bee nest. The distinctive way these bees use plant material to make capsule-like enclosures for their young gave them away. No one had found evidence of these bees at La Brea before.

Leafcutter bees aren’t as well known as their honey- and bumble- relatives, but they’re still around. “They’re everywhere and people just don’t know about them,” Holden says. They’re nonsocial pollinators than zip around dusting their bodies with pollen, which the La Brea leafcutters undoubtedly did as mammoths, sloths, and camels trod around southern California around 40,000 to 35,000 years ago.

But the fossil is more than just a shell. Holden took an X-ray of the prehistoric nest to see if anything might be in side. I can’t repeat her exclamation upon seeing the X-ray here – a joyously-delivered expletive common to scientific discovery – but she was elated to see little blobs indicating that there were leafcutter pupae entombed inside their fragile nest. The next step, with the help of paleontologist Justin Hall, was to CT-scan and visualize the Ice Age bees.

A comparison of a modern leafcutter bee pupa with one of the Ice Age pupae from La Brea. From Holden et al., 2014.
A comparison of a modern leafcutter bee pupa with one of the Ice Age pupae from La Brea. From Holden et al., 2014.

“When I saw the CT reconstructions, I would just play them over and over again,” Holden says. “I just couldn’t believe how well-preserved these pupae were.” The two developing bees were so intricately fossilized, in fact, that Holden and her colleagues were able to identify them as Megachile gentilis – a leafcutter bee that still lives in the American northwest and southwestern Canada.

How could something so delicate become preserved in a place that had totally disarticulated and dissembled countless mammal skeletons? Holden pored over diagrams and field notes to retrace where exactly the nest had been found. The possibility that the bee nest had somehow been washed to its location from somewhere else had to be ruled out. The finely-detailed data collecting standard at La Brea became essential. “I’m very grateful that people were very responsible in taking all that information,” Holden says.

The upshot of all those collection details is that leafcutters really did live at La Brea. Rather than tumbling into a tar pit, Holden says, this nest was made in the ground – just as with living leafcutters – and oil seeped into the cells to effectively embalm the nest and pupae inside. And while such a nest might seem fragile, the fact that leafcutters are ground-nesters means that the bees have to make strong surroundings for their offspring. “I have an understanding now that these nests are much sturdier than they appear,” Holden says. That solid construction and a matter of circumstance saved these bees for the fossil record. “If it wasn’t for this fossilization circumstance, Holden says, “we wouldn’t have these specimens.”

Now, with those specimens in hand, Holden and other Ice Age ecologists can get a finer understanding of what the end-Pleistocene world was like. From what’s known of living Megachile gentilis, Holden says, the presence of this leafcutter species at La Brea indicates that Ice Age Los Angeles was a moister environment with woody habitat near streams. The Pacific Northwest habitats where the bee lives now are a rough proxy for Los Angeles 23,000 years ago, giving us another line of evidence for how changing climate has dramatically altered ecology.

And the pupae may yield even more information about the lost world of the Ice Age. As CT scans get better, paleontologists can see and study small fossils in ever-greater detail. Holden and colleagues might be able to scan the nest again to look for pollen that the nesting bee placed in each cell with the pupae. “Bees are often very specific about the kind of pollen they use,” Holden says, so Ice Age pollen would add even more flourishes to the ecological picture these bees are helping to create.

This fossil is “the gift that keeps on giving,” Holden says. “The yield of paleoecological information is so rich. We learn from the leaves, the bees themselves, even where the nest was found, on the ground at Pit 91.” Some people may still prefer mastodons or short-faced bears, but, given the simple beauty of the bee’s nest and all it can teach us, Holden says “This fossil is my favorite one.”


Holden, A., Koch, J., Griswold, T., Erwin, D., Hall, J. 2014. Leafcutter bee nests and pupae from the Rancho La Brea Tar Pits of Southern California: Implications for understanding the paleoenvironment of the Late Pleistocene. PLoS ONE. 9,4: e94724. doi:10.1371/journal.pone.0094724

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The Worst Places To Get Stung By A Bee: Nostril, Lip, Penis

It started when a honeybee flew up Michael Smith’s shorts and stung him in the testicles.

Smith is a graduate student at Cornell University, who studies the behaviour and evolution of honeybees. In this line of work, stings are a common and inevitable hazard. “If you’re wearing shorts and doing bee work, a bee can get up there easily,” he says. “But I was really surprised that it didn’t hurt as much as I thought it would.”

That got him thinking: Where’s the worst place on the body to get stung?

Everyone who works with stinging insects has their own answers, but Smith couldn’t find any hard data. Even Justin Schmidt was no help. Schmidt is the famous creator of the Schmidt Sting Pain Index—a scale that measures the painfulness of insect stings using wonderful synaesthetic descriptions that almost read like wine-tasting notes. Wine-tasting notes of agony.

According to Schmidt’s index, the sweat bee sting (1 on a scale of 0 to 4) feels like “a tiny spark has singed a single hair on your arm”. The yellowjacket sting (2) is “hot and smoky, almost irreverent; imagine W. C. Fields extinguishing a cigar on your tongue.” And the daddy of stinging insects—the bullet ant (4+)—produces “pure, intense, brilliant pain, like fire-walking over flaming charcoal with a 3-inch rusty nail grinding into your heel.”

Schmidt recognised that “pain levels from particular stings do, of course, vary and depend on such features as where the sting occurred (…)”, but he didn’t say how these levels vary by body part.

So, Smith decided to find out. His experimental subject: himself.

As he writes in his new paper (which, incidentally, is deadpan gold): “Cornell University’s Human Research Protection Program does not have a policy regarding researcher self-experimentation, so this research was not subject to review from their offices. The methods do not conflict with the Helsinki Declaration of 1975, revised in 1983. The author was the only person stung, was aware of all associated risks therein, gave his consent, and is aware that these results will be made public.”

Smith was methodical. He collected bees by grabbing their wings “haphazardly with forceps” and pressing them against the body part of choice. He left the stinger there for a full minute before removing it, and then rated his pain on a scale of 1 to 10.  Pain is very hard to measure, but psychological studies have found that numerical scales do a decent job of putting numbers on an inherently subjective experience.

He administered five stings a day, always between 9 and 10am, and always starting and ending with “test stings” on his forearm to calibrate the ratings. He kept this up for 38 days, stinging himself three times each on 25 different body parts. “Some locations required the use of a mirror and an erect posture during stinging (e.g., buttocks),” he wrote. If you are chuckling at the image of a man twisting around in front of a mirror to apply an agitated bee to his butt, I assure you that you are not alone.

Smith's pain map. Scales are from 1 to 10.
Smith’s pain map. The scale is from 1 to 10.

“All the stings induced pain in the author,” Smith writes. The least painful locations were the skull, upper arm, and tip of the middle toe (all averaging 2.3). “Getting stung on the top of the skull was like having an egg smashed on your head. The pain is there, but then it goes away.”

The most painful sites were the penis shaft (7.3), upper lip (8.7) and nostril (9.0). “It’s electric and pulsating,” he Smith. “Especially the nose. Your body really reacts. You’re sneezing and wheezing and snot is just dribbling out. Getting stung in the nose is a whole-body experience.”

“Erm, but the penis?” I venture.

“It’s painful, and there’s definitely no crossing of wires of pleasure and pain down there,” he says. “But if you’re stung in the nose and penis, you’re going to want more stings to the penis over the nose, if you’re forced to choose.”

Was there any point in the experiment when he thought: Hey, maybe I shouldn’t sting myself in the nose and/or penis?

“By the time I got round to the third round, I thought: I really don’t want to do my nose again,” he says. “I had originally had the eye on the list, but when I talked to [my advisor Tom Seeley], he was concerned that I might go blind. I wanted to keep my eyes.”

There are some interesting nuggets here. We might expect that the most painful places to get stung are the sites that have the thinnest skin or that are served by the most sensory neurons. But neither factor cleanly explains the results. For example, palm with its thick skin hurt much more than the thin-skinned arm or skull. And the upper lip hurt much more than the middle finger, even though both are served by similar numbers of neurons. A pain map of the body would probably look very different to a purely sensory one.

Now, clearly, these data are very subjective, and they all come from one person. Smith is clear that his anatomy of pain can’t be generalised to everyone else. “If someone else did this, they’d probably have different locations that they felt were worst”, he says, although from talking to his colleagues, he feels that the rough shape of the map would be similar.

“I didn’t see a lot of merit in repeating this with more subjects,” he says.

Any takers?

Reference: Smith. 2014. Honey bee sting pain index by body location. PeerJ. http://dx.doi.org/10.7717/peerj.338

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Honeybees can move each other with electric fields

A honeybee returns to its hive after a productive visit to a nearby field of flowers, rich in pollen and nectar. It starts to dance. By waggling its body and strutting in a figure-of-eight, it conveys the duration and direction of the food source to its hive-mates. It was Karl von Frisch, an Austrian scientist, who first deciphered the waggle dance back in 1923. Now, 90 years after his pioneering work, we’re still learning amazing things about the messages that are exchanged within the hive.

When bees fly through the air outside the hive, they collide with charged particles, from dust to small molecules. These impacts tear electrons away from their cuticle—their outer shell—and the bee ends up with a positive charge. When they return to the hive and walk or dance about, they give off electric fields. And Uwe Greggers from the Free University of Berlin has shown that they can detect these fields with the tips of their antennae. Despite our long history with the honeybee, there could still be a secret world of electric communication within the hive that we know nothing about.

We’ve known that insect cuticle builds up electric charge since 1929, almost as long as we’ve known about the waggle dance code. “Many colleagues thought that the bees have a charge but it doesn’t matter. It’s too small,” says Greggers. But when he actually took measurements of living bees, he found that they can produce voltages of up to 450 volts! The insects’ waxy cuticles are responsible—they’re so electrically resistant that a substantial charge can build up and stay there.

Since the 1960s, scientists have speculated that these charges could be useful during pollination. Flowers, after all, tend to have a negative charge on clear days. When bees approach, pollen can actually fly through the air to their bodies. And just last month, Daniel Robert from the University of Bristol showed that bumblebees can detect the electric fields of flowers, and use them to tell the difference between recently visited blooms and fresh ones.

But what about social communication? Can the bees themselves detect each other’s electric fields? Can they extract useful information from them?

To find out, Greggers created Pavlov’s bees. He exposed them to artificial electric fields that mimic those found in the hive, before giving them a rewarding sip of nectar. Soon, he found that the field alone was enough to make them extend their tongues in anticipation of a tasty treat, just like Pavlov’s dogs salivating at the sound of a bell.

Greggers found that the bees detect these fields with their flagella—the very tips of their antennae. Picture a bee, dancing away in a tightly packed hive with many neighbours in close proximity. As it waggles, it also vibrates its wings. As the dancer’s positively-charged wing get closer to a neighbour’s positively-charged antenna, it produces a force that physically repels the antenna. As the dancer’s wing swings back to its original position, the neighbour’s antenna bounces back too. With their electric fields, the bees can move each other’s body parts without ever making contact. (Sure, the beating wing also pushes air past a neighbour’s antenna, but Greggers found that the force produced by the incoming electric field is ten times stronger.)

The bee detects these forces with small touch-sensitive fibres in the joints of their antennae, which send electrical signals towards the insect’s brain. If Greggers immobilised the joints by covering the antennal joints with wax, the bees couldn’t learn to associate electric fields with nectar rewards.

These signals from the fibres are intercepted and processed by a structure called Johnston’s organ within the antennae. By recording the activity of neurons in this organ, Greggers showed that it does indeed fire when an electrically charged object—like a Styrofoam ball—is brought close to the flagellum.

“This is a remarkable discovery,” says Robert. “After all these years of studies on bees, one comes to realise yet another secret aspect to their language. The exact function of such electric sense is not entirely clear but the evidence is strong that electric communication can take place between bees in the hive.

Indeed, now that Greggers has shown that honeybees can detect each others’ electric fields, the big question is: Do they? Is their electric sense an actual part of their everyday lives? To find out, Greggers now wants to study the electric fields of waggle-dancing bees. If he can interfere with the audience’s ability to detect those fields, will that disrupt their ability to interpret the dance?

PS: When I wrote about Roberts’s discovery about bees sensing the electric fields of flowers, the most common comment was something like: “Aren’t our own man-made electromagnetic fields screwing the bees over? The short answer is: No. The fields produced by our technology are actually much lower in energy than those produced by the bees themselves. “They should be naturally protected,” says Greggers. “Unless a bee-keeper puts their hive directly under a high-voltage electric wire outside, the effects should be limited.”

Reference: Greggers, Koch, Schmidt, Durr, Floriou-Servou, Piepenbrock, Gopfert & Menzel. 2013. Reception and learning of electric fields in bees. Proc Roy Soc B http://dx.doi.org/10.1098/rspb.2013.0528

More on bees:

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Bees Can Sense the Electric Fields of Flowers

A bumblebee visits a flower, drawn in by the bright colours, the patterns on the petals, and the aromatic promise of sweet nectar. But there’s more to pollination than sight and smell. There is also electricity in the air.

Dominic Clarke and Heather Whitney from the University of Bristol have shown that bumblebees can sense the electric field that surrounds a flower. They can even learn to distinguish between fields produced by different floral shapes, or use them to work out whether a flower has been recently visited by other bees. Flowers aren’t just visual spectacles and smelly beacons. They’re also electric billboards.

“This is a big finding,” says Daniel Robert, who led the study. “Nobody had postulated the idea that bees could be sensitive to the electric field of a flower.”

Scientists have, however, known about the electric side of pollination since the 1960s, although it is rarely discussed. As bees fly through the air, they bump into charged particles from dust to small molecules. The friction of these microscopic collisions strips electrons from the bee’s surface, and they typically end up with a positive charge.

Flowers, on the other hand, tend to have a negative charge, at least on clear days. The flowers themselves are electrically earthed, but the air around them carries a voltage of around 100 volts for every metre above the ground. The positive charge that accumulates around the flower induces a negative charge in its petals.

When the positively charged bee arrives at the negatively charged flower, sparks don’t fly but pollen does. “We found some videos showing that pollen literally jumps from the flower to the bee, as the bee approaches… even before it has landed,” says Robert. The bee may fly over to the flower but at close quarters, the flower also flies over to the bee.

This is old news. As far back as the 1970s, botanists suggested that electric forces enhance the attraction between pollen and pollinators. Some even showed that if you sprinkle pollen over an immobilised bee, some of the falling grains will veer off course and stick to the insect.

But Robert is no botanist. He’s a sensory biologist. He studies how animals perceive the world around them. When he came across the electric world of bees and flowers, the first question that sprang to mind was: “Does the bee know anything about this process?” Amazingly, no one had asked the question, much less answered it. “We read all of the papers,” says Robert. “We even had one translated from Russian, but no one had made that intellectual leap.”

To answer the question, Robert teamed up with Clarke (a physicist) and Whitney (a botanist), and created e-flowers—artificial purple-topped blooms with designer electric fields. When bumblebees could choose between charged flowers that carried a sugary liquid, or charge-less flowers that yielded a bitter one, they soon learned to visit the charged ones with 81 percent accuracy. If none of the flowers were charged, the bees lost the ability to pinpoint the sugary rewards.

But the bees can do more than just tell if an electric field is there or not. They can also discriminate between fields of different shapes, which in turn depend on the shape of a flower’s petals and how easily they conduct electricity. Clarke and Whitney visualised these patterns by spraying flowers with positively charged and brightly coloured particles. You can see the results below. Each flower has been sprayed on its right half, and the rectangular boxes show the colours of the particles.


Coloured particles reveal the electric fields of flowers. From Clarke et al, 2013
Coloured particles reveal the electric fields of flowers. From Clarke et al, 2013

The bees can sense these patterns. They can learn to tell the difference between an e-flower with an evenly spread voltage and one with a field like a bullseye with 70 percent accuracy.

Bees can also use this electric information to bolster what their other senses are telling them. The team trained bees to discriminate between two e-flowers that came in very slightly different shades of green. They managed it, but it took them 35 visits to reach an accuracy of 80 percent. If the team added differing electric fields to the flowers, the bees hit the same benchmark within just 24 visits.

How does the bee actually register electric fields? No one knows, but Robert suspects that the fields produce small forces that move some of the bee’s body parts, perhaps the hairs on its body. In the same way that a rubbed balloon makes you hair stand on end, perhaps a charged flower provides a bee with detectable tugs and shoves.

The bees, in turn, change the charge of whatever flower they land upon. Robert’s team showed that the electrical potential in the stem of a petunia goes up by around 25 millivolts when a bee lands upon it. This change starts just before the bee lands, which shows that it’s nothing to do with the insect physically disturbing the flower. And it lasts for just under two minutes, which is longer than the bee typically spends on its visit.

This changing field can tell a bee whether a flower has been recently visited, and might be short of nectar. It’s like a sign that says “Closed for business. Be right back.” It’s also a much more dynamic signal than more familiar ones like colour, patterns or smells. All of these are fairly static. Flowers can change them, but it takes minutes or hours to do so. Electric fields, however, change instantaneously whenever a bees lands. They not only provide useful information, but they do it immediately.

Robert thinks that these signals could either be honest or dishonest, depending on the flower. Those that carpet a field and require multiple visits from pollinators will evolve to be truthful, because they cannot afford to deceive their pollinators.  Bees are good learners and if they repeatedly visit an empty flower, they will quickly avoid an entire patch. Worse still, they’ll communicate with their hive-mates, and the entire colony will seek fresh pastures. “If the flower can signal that it is momentarily empty, then the bee will benefit and the flower will communicate honestly its mitigated attraction,” says Robert.

But some flowers, like tulips or poppies, only need one or two visits to pollinate themselves.  “These could afford to lie,” says Robert. He expects that they will do everything possible to keep their electric charge constant, even if a bee lands upon them. They should always have their signs flipped to “Open”. Robert’s students will be testing this idea in the summer.

Many animals can sense electric fields, including sharks and rays, electric fish, at least one species of dolphin, and the platypus. But this is the first time that anyone has discovered this sense in an insect. And in the humble bumblebee, no less! Bees and flowers have been studied intensely for decades, maybe centuries, and it turns out that they’ve been exchanging secret messages all this time.

Now, Robert’s team is going to take their experiments from the lab into the field, to see just how electrically sensitive wild bees can be, and how their senses change according to the weather. “We are probably only seeing the tip of the electrical iceberg here,” he says.

Reference: Clarke, Whitney, Sutton & Robert. Detection and Learning of Floral Electric Fields by Bumblebees. Science http:/dx.doi.org/10.1126/science.1230883

Thanks to Liz Neeley for a chat about dishonest signalling, which inspired part of this piece.

More on electric senses:

More on bees and pollination from National Geographic:


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Reversible gene marks linked to reversible careers in bees

A different version of this story appears at The Scientist.

Honeybee workers spend their whole lives toiling for their hives, never ascending to the royal status of queens. But they can change careers. At first, they’re nurses, which stay in the hive and tend to their larval sisters. Later on, they transform into foragers, which venture into the outside world in search of flowers and food.

This isn’t just a case of flipping between tasks. Nurses and foragers are very distinct sub-castes that differ in their bodies, mental abilities, and behaviour – foragers, for example, are the ones that use the famous waggle dance. “[They’re] as different as being a scientist or journalist,” explains Gro Amdam, who studies bee behaviour. “It’s really amazing that they can sculpt themselves into those two roles that require very specialist skills.” The transformation between nurse and forager is significant, but it’s also reversible. If nurses go missing, foragers can revert back to their former selves to fill the employment gap.

Amdam likens them to the classic optical illusion (shown on the right) which depicts both a young debutante and an old crone. “The bee genome is like this drawing,” she says. “It has both ladies in it. How is the genome able to make one of them stand out and then the other?

The answer lies in ‘epigenetic’ changes that alter how some of the bees’ genes are used, without changing the underlying DNA. Amdam and her colleague Andrew Feinberg found that the shift from nurse to forager involves a set of chemical marks, added to the DNA of few dozen genes. These marks, known as methyl groups, are like Post-It notes that dictate how a piece of text should be read, without altering the actual words. And if the foragers change back into nurses, the methylation marks also revert.

Together, they form a toolkit for flexibility, a way of seeing both the crone and the debutante in the same picture, a way of eking out two very different and reversible skill-sets from the same genome.


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Parasitic fly spotted in honeybees, causes workers to abandon colonies

Throughout North America, honeybees are abandoning their hives. The workers are often found dead, some distance away. Meanwhile, the hives are like honeycombed Marie Celestes, with honey and pollen left uneaten, and larvae still trapped in their chambers.

There are many possible causes of this “colony collapse disorder” (CCD). These include various viruses, a single-celled parasite called Nosema apis, a dramatically named mite called Varroa destructor, exposure to pesticides, or a combination of all of the above. Any or all of these factors could explain why the bees die, but why do the workers abandon the hive?

Andrew Core from San Francisco State University has a possible answer, and a new suspect for CCD. He has shown that a parasitic fly, usually known for attacking bumblebees, also targets honeybees. The fly, Apocephalus borealis, lays up to a dozen eggs in bee workers. Its grubs eventually eat the bees from the inside-out. And the infected workers, for whatever reason, abandon their hives to die.


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How headbutts and dances give bees a hive mind

When we make decisions, our brains are abuzz with agreements and vetoes. Groups of neurons represent different choices, and interact with one another until one rises to the fore. The neurons excite some of their neighbours into firing in tandem, while suppressing others into silence. From this noisy cross-talk, a choice emerges.

The same thing happens in a bee hive. The entire colony, consisting of tens thousands of individuals, works like a single human nervous system, with each bee behaving like a neuron. When they make a decision, such as choosing where to build a nest, individual bees opt for different choices and they support and veto each other until they reach a consensus. They have, quite literally, a hive mind.


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Faecal diet gives bumblebees defensive bacteria that protect them from parasites

Bumblebees begin their adult lives by eating their sisters’ faeces. After many months as helpless, hungry larvae, they spin a silken cocoon and transform their bodies. When they emerge, ready to face the world, they get mouthfuls of poo.  It may not sound like an auspicious start, but it’s essential. The faeces contain special bacteria that act as part of the bee’s immune system, protecting it from an incredibly dangerous parasite.

Gut bacteria are important partners for many animals. We humans have up to 100 trillion microbes in our bowels, and this “microbiota” outnumbers our own cells by ten to one. They act like a hidden, writhing organ. They break down our food. They influence our behaviour. And they safeguard our health by crowding out other bacteria that could cause disease. It seems that gut bacteria play a similar role in bumblebees.


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Eight-year-old children publish bee study in Royal Society journal


“We also discovered that science is cool and fun because you get to do stuff that no one has ever done before.”

This is the conclusion of a new paper published in Biology Letters, a high-powered journal from the UK’s prestigious Royal Society. If its tone seems unusual, that’s because its authors are children from Blackawton Primary School in Devon, England. Aged between 8 and 10, the 25 children have just become the youngest scientists to ever be published in a Royal Society journal.

Their paper, based on fieldwork carried out in a local churchyard, describes how bumblebees can learn which flowers to forage from with more flexibility than anyone had thought. It’s the culmination of a project called ‘i, scientist’, designed to get students to actually carry out scientific research themselves. The kids received some support from Beau Lotto, a neuroscientist at UCL, and David Strudwick, Blackawton’s head teacher. But the work is all their own.

The class (including Lotto’s son, Misha) came up with their own questions, devised hypotheses, designed experiments, and analysed data.  They wrote the paper themselves (except for the abstract), and they drew all the figures with colouring pencils.

It’s a refreshing approach to science education, in that it actually involves doing science. The practical sessions in modern classrooms are a poor substitute; they might allow students to get their hands dirty, but they are a long way from true experiments. Their answers are already known and they do nothing to simulate the process of curiosity and discovery that lie at the heart of science. That’s not the case here. As the children write, “This experiment is important, because no one in history (including adults) has done this experiment before.” (more…)

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Sperm war – the sperm of ants and bees do battle inside the queens

One night of passion and you’re filled with a lifetime full of sperm with no need to ever mate again. As sex lives go, it doesn’t sound very appealing, but it’s what many ants, bees, wasps and termites experience. The queens of these social insects mate in a single “nuptial flight” that lasts for a few hours or days. They store the sperm from their suitors and use it to slowly fertilise their eggs over the rest of their lives. Males have this one and only shot at joining the Mile High Club and they compete fiercely for their chance to inseminate the queen. But even for the victors, the war isn’t over. Inside the queen’s body, their sperm continue the battle.

If the queen mates with several males during her maiden flight, the sperm of each individual find themselves swimming among competitors, and that can’t be tolerated. Susanne den Boer from the University of Copenhagen has found that these insects have evolved seminal fluids that can incapacitate the sperm of rivals while leaving their own guys unharmed. And in some species, like leafcutter ants, the queen steps into the fray herself, secreting chemicals that pacify the warring sperm and ease their competition.

The amazing thing about this chemical warfare is that it has evolved independently several times. Social insects evolved from ancestors that observed strictly monogamous relationships. Even now, the queens from many species mate with just one male during their entire lives. With just one set of sperm in their bodies, they have no problem with sperm conflict. The trouble starts when species start mating with several males during their nuptial flights, as honeybees, social wasps, leafcutter ants, army ants, and others do today. 


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Bee-ware – bees use warning buzz to refute the waggle dance

Bees can communicate with each other using the famous “waggle dance”. With special figure-of-eight gyrations, they can accurately tell other hive-mates about the location of nectar sources. Karl von Frisch translated the waggle dance decades ago but it’s just a small part of bee communication. As well as signals that tell their sisters where to find food, bees have a stop signal that silences dancers who are advertising dangerous locations. 

The signal is a brief vibration at a frequency of 380 Hz (roughly middle G), that lasts just 150 milliseconds. It’s not delivered very gracefully. Occasionally, the signalling bee will use a honeycomb to carry her good vibrations, but more often than not, she’ll climb on top of another bee first or use a friendly headbutt. The signal is made when bees have just travelled back from a food source where they were attacked by rivals or ambush predators. And they always aim their buzzes at waggle dancers. The meaning is clear; it says, “Don’t go there.”

These signals were identified decades ago, but scientists originally interpreted them as a begging call, intended to cadge some food of another worker.  It seems like a strange conclusion, when you consider that the signals never actually prompt workers to exchange food. Their true nature became clearer when scientists showed that playing them through speakers could stop dancers from waggling.


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Mathematical support for insect colonies as superorganisms

The mighty insect colonies of ants, termites and bees have been described as superorganisms. Through the concerted action of many bodies working towards a common goal, they can achieve great feats of architecture, agriculture and warfare that individual insects cannot.

That’s more than just an evocative metaphor. Chen Hou from Arizona State University has found that the same mathematical principles govern the lives of insect colonies and individual animals. You could predict how quickly an individual insect grows or burn food, how much effort it puts into reproduction and how long it lives by plugging its body weight into a simple formula.  That same formula works for insect colonies too, if you treat their members as a collective whole.

Life is fundamentally about the use of energy, about effectively harvesting it from food and channelling it into existence and offspring. As animals get bigger, their changing use of energy ripples across all aspects of their lives. Because of economies of scale, larger and more complex animals need less energy for each individual cell. They grow and reproduce more slowly and they live longer.

The astounding thing is that this variety can be captured by a deceptively simple equation. An animal’s metabolic rate is proportional to its mass to the power of three-quarters (0.75). So a cat that is 100 times heavier than a mouse would have a metabolic rate that was around 32 times greater, and a human that is 10 times heavier than a cat would have a metabolic rate around 6 times greater. This beautiful three-quarters “power law” links all animals from mice to elephants.

Hou showed that it applies to insect colonies. He gathered data on over 168 species of social insects and noted the total mass of all their members. They ranged from species of fire ants whose colonies weigh little more than 2 milligrams, to African termite colonies that tip the scales at around 4kg.


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Buzzing bees scare elephants away

This article is reposted from the old WordPress incarnation of Not Exactly Rocket Science. The blog is on holiday until the start of October, when I’ll return with fresh material.

It’s a myth that elephants are afraid of mice, but new research shows that they’re not too keen on bees. Even though they fearlessly stand up to lions, the mere buzzing of bees is enough to send a herd of elephants running off. Armed with this knowledge, African farmers may soon be able to use strategically placed hives or recordings to minimise conflicts with elephants.

Elephants turn tail at the sound of beesIain Douglas-Hamilton and Fritz Vollrath from Kenyan conservation charity Save the Elephants first suspected this elephantine phobia in 2002, when they noticed that elephants were less likely to damage acacia trees that contained beehives.

Animals as powerful as the African elephant can go largely untroubled by predators. Their bulk alone protects them from all but the most ambitious of lion prides.

But these defences do nothing against the African bees, which can sting them in their eyes, behind their ears and inside their trunks. Against these aggressive insects, the elephants are well justified in their caution and local people have reported swarms of bees chasing elephants for long distances.

Lucy King, a graduate student from the University of Oxford confirmed this theory by using camouflaged wireless speakers to play recordings of angry buzzing bees to herds of elephants resting under trees.