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This Beetle is Ruining Your Coffee With the Help of Bacteria

I am writing a book about partnerships between animals and microbes. In the process, I have consumed a frankly obscene amount of coffee, to the extent that the dedication might just read “To coffee, with thanks”. So, it is with mixed emotions that I now write this post, about an animal that is ruining coffee with the help of bacteria.

The coffee berry borer is a small, black beetle, just a few millimetres long. The females bore holes into coffee berries and then lay their eggs in the seeds within—the bits that we know as “coffee beans”. The larvae devour the seeds when they hatch, destroying them. In Brazil alone, its antics lead to some 300 million dollars worth of losses, and it has spread to coffee-making nations all over the world. This tiny pest is the single greatest threat to your cup of blissful java.

Coffee berry borer beetle. Credit: L. Shyamal (CC BY-SA 3.0)
Coffee berry borer beetle. Credit: L. Shyamal (CC BY-SA 3.0)

The beetle is the only animal that can feed solely on coffee beans. Others might occasionally nibble the seeds or other parts of the coffee plant, but they don’t dedicate themselves to the task. There’s a reason for that: caffeine. This stimulant draws many of us to coffee, but it effectively deters plant-eating animals. Not only does it taste bitter, but at the doses found in coffee seeds, it can poison and paralyse any wayward insect. Any insect, that is, except for the coffee berry borer. As a larva, it’s practically bathed in caffeine, and yet it survives. Even the most caffeine-rich beans fail to deter it.

Javier Ceja-Navarro from the Lawrence Berkeley National Laboratory has discovered its secret: it has bacteria in its guts that can detoxify caffeine.

When he fed the beetles with coffee beans and analysed their faeces for traces of caffeine, he couldn’t find any. None. Something in their gut had completely destroyed the would-be poison. Bacteria seemed like the obvious candidates, so Ceja-Navarro fed the beetles with antibiotics. This time, when they ate coffee beans, their poo was laden with caffeine. And when they got a chance to breed, they utterly failed. Most of their eggs and larvae died outright, and none of the survivors made it to adulthood. Without their microbes, they couldn’t handle their caffeine.

Ceja-Navarro’s team, led by Eoin Brodie, found that the bacteria in the coffee berry borer’s gut vary from country to country, but some species turn up everywhere. At least a dozen of these can grow on caffeine and nothing else, and one—Pseudomonas fulva—was especially good at it. It’s was the only microbe with a gene called ndmA, which starts the process of metabolising caffeine.

When Ceja-Navarro fed P.fulva to the antibiotic-treated beetles, he restored their ability to metabolise caffeine. Then again, the insects still couldn’t reproduce, which suggests that other bacteria also affect its health, and perhaps its ability to withstand its toxic meals.

Whether this discovery will help coffee farmers is not clear. It would be a truly terrible idea to start spraying coffee plants with antibiotics, but perhaps there might be subtler ways of breaking the alliances between the beetles and their detoxifying microbes.

Detoxification is only one part of the coffee berry borer’s success. There’s also digestion. Coffee berries are 60 percent carbohydrates, and since the beetle larvae eat nothing else, they need some way of breaking down these large, tough molecules.

In 2012, Ricardo Acuña from Cenicafé, a Colombian coffee research centre, discovered its trick by analysing the genes that are switched on in its guts. One of them – HhMAN1 – stood out for two reasons. First, it creates a protein called mannanase that breaks down galactomannan, one of the major carbohydrates in coffee beans. Second, insects aren’t meant to have mannanases.

Acuña found that the beetle’s version of HhMAN1 is most closely related to genes from bacteria. He checked to make sure that he hadn’t sequenced some contaminating microbe, and indeed he hadn’t: HhMAN1 was surrounded by other typical insect genes and was clearly a bona fide part of the beetle genome.

So, at some point in their history, these beetles stole a gene from bacteria, perhaps the same ones that live in its gut. That gene now lives permanently in their genome and allows them to digest the signature carbohydrates found in coffee beans.

Bacteria, then, have helped the beetle in two ways—by donating a digestive gene at some point in the distant past, and by donating their detoxifying powers in the present. Boosted by microbial power, the beetle has become a worldwide pest, and a royal pain-in-the-espresso.

Reference: Ceja-Navarro, Vega, Karaoz, Hao, Jenkins, Lim, Kosina, Infante, Northern & Brodie. 2015. Gut microbiota mediate caffeine detoxification in the primary insect pest of coffee. Nature Communications http://dx.doi.org/10.1038/ncomms8618


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Rhino Beetle Weapons Match Their Fighting Styles

When longswords first came into use in the 13th century, knights mainly used them to slash through an opponent’s chainmail. But once plate armour entered the battlefield, these slashes were useless. Now, sword-wielders had to thrust their weapons into gaps and weak points—a new kind of fighting that required a different kind of blade. Longswords evolved to be longer, narrower, and more pointed. The central groove (the fuller) that lightened and strengthened the old models was replaced by a ridge (the riser) that conferred rigidity. A cutting weapon became more of a stabbing one. Form followed function.

Erin McCullough from the University of Montana found a similar trend among smaller but no less impressively armed combatants—rhinoceros beetles. As their name suggests, the males of these large, powerful insects have elaborate horns on their heads. In many animals, females choose males on the size and shape of their ornate structures. But that’s not the case for the rhino beetles. Their horns are purely weapons. They’re for grabbing, throwing and shoving rival males off branches and tree trunks, in a bid to control access to females.

Hercules beetle. Credit Udo Schmidt.
Hercules beetle. Credit Udo Schmidt.

Each species of rhino beetle has its own distinctive headgear, and each fights in a different style.  The largest of them, the Hercules beetle (Dynastes hercules) has a huge horn curving down from its back and another curving up from its head. It looks like a disembodied pincer, and behaves like one too—males grab their opponents in a full-body hold, prise them off their perch, and toss them to the ground. (It can lift 850 times its own weight and, until recently, held the title of world’s strongest animal .)

The calliper beetle (Golofa porteri) has a much narrower horn with a serrated edge, which it uses to lift and shove its opponent—more of a fencer to the Hercules beetle’s wrestler. And the Japanese rhino beetle (Trypoxylus dichotomus), much beloved of cartoons and anime, has an upwardly curving horn that ends in a pitchfork. During fights, it tries to slide this tip under its opponent, to lift and twist it off its branch.

“Your Hercules Beetle style is no match for my Caliper Beetle Fist Technique.” Different fighting moves of the Japanese rhino beetle (top), Hercules beetle (middle) and caliper beetle (bottom).
"Your Hercules Beetle technique is no match for my Caliper Beetle form!" Different fighting styles of the Japanese rhino beetle (top), Hercules beetle (middle), and caliper beetle (bottom). Illustrations by David J. Tuss

McCullough has found that the shape and structure of these horns are beautifully adapted to each beetle’s individual fighting style. Each one resists the types of forces that its owners typically experience, but threatens to snap or buckle when used in a different way. As with the longswords, form and function are linked.

This study wouldn’t have been possible through direct experiments. You can’t just pack a rhino beetle off to a new dojo, train it in a different martial art, and see how it performs. But McCullough did something similar, using a technique called finite element analysis (FEA). It’s a digital crash-test. You scan an object to create a three-dimensional virtual model, and then subject that model to forces of your choice. Engineers use it to simulate collisions between vehicles and obstacles. Biologists have used it to simulate collisions between jaws and prey. And McCullough used it to simulate collisions between beetles. In her computer, she could watch what happens if one rhino beetle fought its rivals in the style of another.

And what happens is: the horns do badly. For example, if you apply twisting forces to a Japanese rhino beetle’s horn, it holds up well. The virtual models are coloured in cool blues and greens, indicating low levels of mechanical stress. But if you twist the horns of the other two beetles, they light up in fierce reds and whites. In real life, they’d probably snap. In all three cases, McCullough found that the horns were least likely to snap or bend, when used in the directions that the beetles actually use them.

Cross-sections of the horns of the three beetles. Credit: McCullough et al, 2014. PNAS.
Cross-sections of the horns of the three beetles. Credit: McCullough et al, 2014. PNAS.

Some studies have shown that horned mammals also fight in ways that suit their headgear. Curved-horn sheep ram each other, short-horned gazelles stab, and long-horned oryxes wrestle. But none of these studies checked if the horns actually work best in these conditions, and whether they’d suit other techniques  equally well. McCullough did that with her virtual crash-tests. “It’s intuitive but this is the first real direct evidence of that hypothesis,” she says. “It shows the possibility of using this new tool—finite element analysis—for understanding weapon diversity.”

She also correctly predicted the cross-sectional shapes of the three beetles’ horns, based on their fights. The Hercules beetle mostly uses its horn to grab and lift, so its ideal cross-section is an oval that’s vertically wide and horizontally narrow. The calliper beetle’s horn is used in more versatile ways and needs to resist forces in most directions—it should have a circular cross-section. And since the Japanese rhino beetle’s horn often twists, it would benefit from a U-shaped or a triangular cross-section resists bending and twisting. And that’s pretty much what the three horns are actually like. Based on function, you can predict form.

McCullough says that the results show how “male–male competition can drive the diversification of animal weapons”. But I wondered if the beetles could instead be fighting in a way that makes best use of their horns? A human fighter wouldn’t try to pummel someone with a dagger or to stab someone with a mace. Maybe function follows form?

“I get asked that a lot,” she says. She thinks that behaviour is probably more flexible than horn structure, so it’s more likely that the former changed to fit the latter than the other way round. But the only way to be sure is to test a wider range of beetles and to see how both their weapons and their combat techniques changed as the group diversified. Her group, led by Doug Emlen, is now working on that.

For more on the rhino beetles and other weapons, you may want to check out Doug Emlen’s upcoming book Animal Weapons: The Evolution of Battle.

Reference: McCullough, Tobalske & Emlen. 2014. Structural adaptations to diverse fighting styles in sexually selected weapons. PNAS http://dx.doi.org/10.1073/pnas.1409585111



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Meet The Predator That Becomes Blind When It Runs After Prey

The tiger beetle can run so fast that it blinds itself.

There are 2,600 species of these long-legged predatory insects, and the fastest can sprint at up to 5 miles per hour, covering 120 of its body lengths in a single second. For comparison, Usain Bolt covers just 5 body lengths per second. To match the beetle, he’d have to run at 480 miles per hour.

Tiger beetles use this incredible speed to run down both prey and mates. But as they sprint, their environment becomes a blur because their eyes simply can’t gather enough light to form an image. They have extremely sharp vision for insects, but when they’re running, the world smears into a featureless smudge. To compensate, the beetle has to stop to spot its prey again, before resuming the chase.

It seems like a bad evolutionary joke: a hunter that loses sight of its prey whenever it runs.

But tiger beetles don’t mind because… well… they are really, really fast. They can afford to stop in the middle of a chase because they are so ridiculously quick when they’re in motion. It’s like the aforementioned Bolt pausing at the 50-metre mark for a drink, and still winning.

Hairy-necked tiger beetle. Credit: Daniel Zurek.
Hairy-necked tiger beetle. Credit: Daniel Zurek.

Cole Gilbert at Cornell University discovered the tiger beetles’ staccato hunting style in 1998. Now, together with Daniel Zurek, he has worked out how they cope with another problem: obstacles.

At high speed, it’s hard enough to avoid incoming obstacles. But try doing it when your eyes can’t make out anything, much less small pebbles or sticks. A running tiger beetle is permanently in “collision mode”, says Zurek. “It’s like when I’m driving a car really fast and not wearing my glasses. When something hops in the road, I can’t stop in time.”

He discovered how they cope by watching an American species—the hairy-necked tiger beetle, Cicindela hirticollis. When it runs, it always keeps its antennae in the same fixed position: straight ahead, angled at a V, and held slightly above the ground. The antennae can move, but they never do while the beetle’s in motion.

The antennae are obstacle-detectors. If they hit an obstacle, their flexible tips bend back before springing forwards again. The beetle moves too fast to change course, but it can tip its body slightly upwards so that it skitters over the obstacle rather than running headlong into it. It’s like a blind person holding two white canes (and wearing rocket skates).

“Because of their shape, the antennae can slip over the edge of an obstacle, which tells the beetles that there’s a top they can run over,” says Zurek. He saw how effective this is by filming tiger beetles running down a long track with a piece of wood in the middle. If their antennae were intact, they cleared the obstacle most of the time, even when Zurek painted over their eyes. But if he cut the antennae off, the beetles frequently face-planted into the wood.

This solution is not only effective, but cheap. The beetles could potentially deal with motion blur by evolving more sensitive eyes, but it takes a huge amount of energy to pay for an eye with good temporal resolution. They would also have to analyse that information, and their small brains probably don’t have the processing power. Fortunately, they don’t need anything that over-engineered.  Their antennae provide them with all the collision-detection they need.

Zurek thinks that human engineers should take note. One of the first autonomous robots—Shakey—found its way around with some “bump detectors”. If they hit an obstacle, they bent, and Shakey would back up.

But modern robots rely on cameras. NASA’s Curiosity rover, for example, is currently trundling over Mars with the help of eight hazard avoidance cameras, or Hazcams. “As humans, we tend to think first and foremost from a visual standpoint,” he says. “Many really sophisticated robots rely on an array of cameras that analyse on the fly, which is very computationally intensive.” The tiger beetle’s solution would be simpler, and might help robots to move much faster than Curiosity’s leisurely pace.

PS: How does one catch an insect that moves so quickly? With great difficulty at first, but Zurek says, “It’s pretty fun once you get the hang of it,” he says. “You have to fool them by coming up behind them really slowly and then lowering yourself. I get them around 60 percent of the time.”

Reference: Zurek & Gilbert. 2014. Static antennae act as locomotory guides that compensate for visual motion blur in a diurnal, keen-eyed predator. Proceedings of the Royal Society B http://dx.doi.org/10.1098/rspb.2013.3072

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Dung Beetles Watch the Galaxy (That’s How They Roll)

From all across the galaxy, the light of billions of stars finds its way to Earth, passes through our atmosphere, and enters the eyes of a small South African beetle rolling a ball of dung. The beetle’s eyes are not sensitive enough to pick out individual stars but it can see the Milky Way as a fuzzy stripe, streaking across the night sky. With two of its four eyes, it gazes into the guts of our galaxy, and uses starlight to find its way home.

Dung beetles eat the droppings of other animals. They congregate upon piles of fresh dung, gather it into tasty balls and roll it home. Competition at a dung pile is intense and the path home can be long, dangerous and tiring. So, it pays the beetle to keep the straightest possible course.

Like many insects, dung beetles that roll in the day can detect the way that sunlight changes as it enters the Earth. Light behaves like a wave that normally vibrates in every possible direction. When it hits particles in the atmosphere, it becomes polarised, so it only vibrates in one direction depending on where the sun is in the sky. Many insects can see these patterns of polarised light, which are invisible to us, and use them to orient themselves.

Keeping a straight line is even harder at night, and even humans veer off in a curve if we can’t see anything. “For beetles with poor-resolution compound eyes, it pays to grab a hold of any visual cues in the night sky to help them steer straight,” says Ken Cheng from Macquarie University. Some use the moon, which also produces patterns of polarised light, albeit a million times dimmer than those from the sun. In 2003, Eric Warrant from Lund University found that some dung beetles, which come out at night can use these patterns to keep their paths straight.

But one beetle, known as Scarabaeus satyrus, was doing something else. Warrant and his colleague Maria Dacke noticed that even on clear, moonless nights, this species could keep a reasonably straight course. “We thought this was odd,” he says. Perhaps the beetles were navigating by starlight? Humans, birds and seals can certainly use the constellations to find their way around, but we all share similar eyes. Could an insect’s eyes use the same cues?

Dacke and Warrant found out by capturing dung beetles and placing them in a circular open-topped arena, surrounded by black walls to obscure the sight of any landmarks. The beetles were raised into the middle of the arena with their faecal cargo. They rolled off and once they hit the edge, they fell through a small gap and made an audible thump. Since each beetle rolls at a constant speed, Dacke and Warrant could measure how far they had travelled by marking the time between their entrance into the arena and the sound of their exit.

Under a full moon, they took 21 seconds. Under a moonless, starry night, their paths wavered more and they took 40 seconds. On a cloudy night, or if Dacke and Warrant covered their heads with a black cap (this isn’t the first time they’ve dressed up dung beetles for science), the beetles took around 120 seconds to reach the edge.

Dung beetle rolling a dung ball with a cap taped to its head. (This one is transparent, so the beetle can still see through it.) Credit: Eric Warrant

Dung beetles roll their balls backwards, walking face-down and pushing with their hind legs. That seems like the wrong position for stargazing, but they have two pairs of eyes, one pointing up and one pointing down. It’s the upwards pair that sees the stars.

But to work out what they are actually seeing, Dacke and Warrant couldn’t just cover the beetle’s eyes. They had to somehow manipulate the night sky itself. So they took their beetles and arenas to the planetarium at the University of the Witwatersrand in Johannesburg.

If they projected the bright stripe of the Milky Way onto the building’s 18-metre domed ceiling, the beetles could find their way out of the arena reasonably quickly. It didn’t matter whether the team added another 4,000 stars—it was the Milky Way that mattered. If they left out this galactic stripe, or only added the 18 brightest stars, the beetles took much longer to find their way out.

“I really like the simplicity of their experiments. They’re delicious and simple like sushi,” says Lars Chittka, an insect expert at Queen Mary University of London. “It shows that even in the post-genomic world, the best science is still often driven by ideas rather than expensive equipment.”

This isn’t the first time that scientists have brought animals to planetariums to test their navigation. They’ve used these artificial domes to show that indigo buntings, flying south for the winter, navigate by flying away from the North Star. The dung beetles, however, clearly aren’t focusing on a single bright star. Instead, they’re using the collective light of billions of them.

“Have the beetles specifically evolved the ability to navigate by using the Milky Way, or are they just opportunistically using any landmark that stays in place for the duration of their path?” Chittka wonders. “The Milky Way might not have a special salience for the beetles, but just be one of a class of cues that can be used to maintain a constant direction, such as a tree, a mountain, the sun, or the moon.”

Reference: Dacke, Baird, Byrne, Scholtz & Warrant. 2013. Dung Beetles Use the Milky Way for Orientation. Current Biology http://dx.doi.org/10.1016/j.cub.2012.12.034

More on dung beetles:


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Wormholes in old books preserve a history of insects

Absence can speak volumes. The lack of sediment in a flat piece of ground—a track—can testify to the footstep of a dinosaur that once walked on it. The lack of minerals in a solid shell—a hole—can reveal the presence of parasite that was once trapped in it. The world’s museums are full of such “trace fossils”, but so are many of the world’s art galleries.

The image above is taken from a woodcut currently residing in Amsterdam’s Rijksmuseum. It was made by etching a pattern into a block of wood, so that the remaining raised edges could be dipped in ink and used to print an image. These woodcuts were the main way of illustrating European books between the 15th and 19th centuries, and were used for at least 7 million different titles.

But as you can see, the print is littered with tiny white holes. These are called wormholes, and inaccurately so—they’re actually the work of beetles. The adults laid their eggs in crevices within the trunks of trees. The grubs slowly bored their way through the wood, eventually transformed into adults, and burrowed their way out of their shelters. The artists who transformed the tree trunks into printing blocks also inherited the exit-holes of the adult beetles, which left small circles of empty whiteness when pressed onto pages.

The beetles only emerged a year or so after the blocks were carved. The holes they left must have been frustrating, but remaking them would have been expensive. So the blocks were kept and reused despite their defects, unless the beetles had really gone to town. The holes they left behind preserve a record of wood-boring beetles, across four centuries of European literature. These holes are trace fossils. They’re evidence of beetle behaviour that’s been printed into old pages, just as dinosaur tracks were printed into the earth.

Now, Blair Hedges from Pennsylvania State University has used these fossils to study the history of the beetles that made them.


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To find out why this beetle has a spiky penis, scientists shaved it with lasers

The thing in the photo above, I’m sad to say, is a penis. It belongs to the male seed beetle. And just in case you’re holding out hope that appearances are deceiving, I can assure you they are not. Those spikes are hard and sharp, and they inflict heavy injuries upon the female beetles during sex. Why would such a hellish organ evolve?

This isn’t just about beetles. The animal kingdom is full of bafflingly-shaped penises adorned with spines, spikes, and convoluted twists and turns. In some animal groups, like certain flies, penis shape is the only clue that allows scientists to distinguish between closely related species.

For a male, sex isn’t just about penetration. After he ejaculates inside a female, his sperm still have to make their way to her eggs to fertilise them and pass on his genes. If she mates with many suitors, her body becomes a battleground where the sperm of different males duke it out. Females can influence this competition by being choosy over mates, storing sperm in special pouches, or evolving their own convoluted genital passages. Males, meanwhile, have evolved their own tricks, including: guarding behaviour; self-castration; barbed sperm; chemical weapons in their sperm; mating plugs; ‘traumatic insemination’; and having lots of sperm.

And spiky penises. That too.


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This dung beetle’s air-conditioning unit is crap. No, really

Here’s a dung beetle, sitting on a ball of poo that it made earlier, wearing a pair of adorable insulating mitts. We’ll get to the mitts later…

The dung beetle, Scarabaeus nigroaeneus, as its name suggests, eats the faeces of large grazing mammals. When it finds a fresh pat, it fashions the dung into a ball and rolls it home, head down and walking backwards. That’s hard work. The balls can be 50 times heavier than the beetle, whose body heats up as it pushes around its weighty cargo.

Heating up is something that an insect can’t afford to do in the South African desert, where the ground can reach a scorching 60 degrees Celsius in the middle of the day. But the beetle’s dung-rolling antics provide it with a constantly accessible way of beating the heat. By filming dung beetles with a heat-sensitive camera, Jochen Smolka from Lund University has found that their dung balls aren’t just take-away meals—they’re also portable coolers.


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Beetle walks and sticks underwater by creating dryness with every footstep

Sticking to surfaces and walking up walls are so commonplace among insects that they risk becoming boring. But the green dock beetle has a fresh twist on this tired trick: it can stick to surfaces underwater. The secret to its aquatic stride is a set of small bubbles trapped beneath its feet. This insect can plod along underwater by literally walking on air.

The green dock beetle (Gastrophysa viridula) is a gorgeous European resident with a metallic green shell, occasionally streaked with rainbow hues. It can walk on flat surfaces thanks to thousands of hairs on the claws of their feet, which fit into the microscopic nooks and crannies of whatever’s underfoot. Most beetles have the same ability, and some boost the adhesive power of their hairs by secreting a sticky oil onto them.

These adaptations work well enough in dry conditions, but they ought to fail on wet surfaces. Water molecules should interfere with the hairs’ close contact, and disrupt the adhesive power of the oil. “People believed that beetles have no ability to walk under water,” says Naoe Hosoda from the National Institute for Material Science in Tuskuba, Japan.

They were clearly wrong. Together with Stanislav Gorb from the Zoological Institute at the University of Kiel, Germany, she clearly showed that the green dock beetle has no problems walking underwater. The duo captured 29 wild beetles, and allowed them to walk off a stick onto the bottom of a water bath. Once there, they kept on walking. (more…)

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Fire-chasing beetles sense infrared radiation from fires hundreds of kilometres away

In the 1940s, visitors watching football games at Berkeley’s Californian Memorial Stadium would often be plagued by beetles. The insects swarmed their clothes and bit them on the necks and hands. The cause: cigarettes. The crowds smoked so heavily that a cloud of smoke hung over the stadium. And where there’s smoke, there’s fire. And where there’s fire, there are fire-chaser beetles.

While most animals flee from fires, fire-chaser beetles (Melanophila) head towards a blaze. They can only lay their eggs in freshly burnt trees, whose defences have been scorched away. Fire is such an essential part of the beetles’ life cycle that they’ll travel over 60 kilometres to find it. They’re not fussy about the source, either. Forest fires will obviously do, but so will industrial plants, kilns, burning oil barrels, vats of hot sugar syrup, and even cigarette-puffing sports fans.

The beetles find fire with a pair of pits below their middle pair of legs. Each is only as wide as a few human hairs, and consists of 70 dome-shaped sensors. They look a bit like insect eyes. In the 1960s, scientists showed that the sensors detect the infrared radiation given off by hot objects. Each one is filled with liquid, which expands when it absorbs infrared radiation. This motion stimulates sensory cells and tells the beetle that there’s heat afoot.


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Beetle pest destroys coffee plants with a gene stolen from bacteria

For fans of a velvety latte or a jolting espresso, meet your greatest enemy: the coffee berry borer beetle. This tiny pest, just a few millimetres long, can ruin entire coffee harvests. It affects more than 20 million farming families, and causes losses to the tune of half a billion US dollars every year- losses that are set to increase as the world warms.

But the beetle isn’t acting alone. It has a secret weapon, stolen from an unwitting accomplice.

Ricardo Acuña has found that the beetle’s ancestors pilfered a gene from bacteria, most likely the ones that live in its gut. This gene, now on permanent loan, allows the insect to digest the complex carbohydrates found in coffee berries. It may well have been the key to the beetle’s global success.


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Burgling beetle targets plants with the heaviest security

Heavy locks, imposing gates and motion-sensing lights can help to fortify your home and safeguard your belongings against thieves. On the other hand, they can also advertise the fact that you have stuff worth stealing. Extra security can be a double-edged sword.

This is as true for plants defending their tissues as it is for humans defending their homes. Maize plants, like many others, protect themselves with poisons. They pump their roots with highly toxic insecticides called BXDs, which deters hungry mandibles. But these toxins don’t come free. The plant needs energy to act as its own pharmacist, so it distributes the poison to the areas that deserve the greatest fortification – its crown roots.


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Beetle larva lures and kills frogs, while the adult hunts and paralyses them

During its lifetime, a frog will snap up thousands of insects with its sticky, extendable tongue. But if it tries to eat an Epomis beetle, it’s more likely to become a meal than to get one. These Middle Eastern beetles include two species – Epomis circumscriptus and Epomis dejeani – that specialise at killing frogs, salamanders, and other amphibians.

Their larvae eat nothing else, and they have an almost 100 percent success rate. They lure their prey, encouraging them to approach and strike. When the sticky tongue lashes out, the larva dodges and latches onto its attacker with wicked double-hooked jaws. Hanging on, it eats its prey alive. The adult beetle has a more varied diet but it’s no less adept at hunting amphibians. It hops onto its victim’s back and delivers a surgical bite that paralyses the amphibian, giving the beetle time to eat at its leisure.


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Beetles turn eggs into shields to protect their young from body-snatchers

Some parents give their children a head start in life by lavishing them with money or opportunities. The mother seed beetle (Mimosestes amicus) does so by providing her children with shields to defend them from body-snatchers.

A female seed beetle abandons her eggs after laying them. Until they hatch, they are vulnerable to body-snatching parasites, like the wasp Uscana semifumipennis. It specialises on seed beetle eggs and lays its own eggs inside. Once the wasp grub hatches, it devours its host. The wasp problem is so severe that around 70 percent of the beetles’ eggs can be infested.

But the mother seed beetles have a defence, and it is a unique one. Joseph Deas and Molly Hunter from the University of Arizona have found that they can protect an egg from this grisly fate by laying another one on top. Sometimes, the mothers lay entire stacks of two or three eggs. The tops ones are always flat and unviable. They never hatch into grubs and they completely cover the ones underneath.


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Beetle turns itself into a wheel (that’s how it rolls)

The southern beaches of Cumberland Island, off the coast of Georgia, USA, are part of a national park. To protect the area, only residents and staff are allowed to drive their vehicles on the sands. But there are plenty of wheels nonetheless – small, living ones.

The beaches are home to the beautiful coastal tiger beetle (Cicindela dorsalis media). Tiger beetles are among the fastest of insect runners, but their larvae are slow and worm-like. If they’re exposed and threatened, running isn’t an option. Instead, they turn themselves into living wheels. They leap into the air, coil their bodies into a loop, and hit the ground spinning. The wind carries them to safety.

The fact that a long, worm-like animal can jump and roll is amazing in its own right. The ability is even more remarkable because the tiger beetle is “one of the best-studied insect species in North America” and until a few years ago, no one had ever seen it doing this. Alan Harvey and Sarah Zukoff were the first. They write, “[Sarah] was walking through some unusually loose sandy drifts on Cumberland Island and happened to kick up some C. d. media larvae, which promptly started wheeling.”


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The beetle with bifocal eyes

SunburstBifocal glasses allow wearers to focus on both far and near objects by looking through different parts of the lens. It’s commonly said that Benjamin Franklin invented these lenses, but they have actually been around for millions of years. In the streams of North America, the nightmarish larva of the sunburst diving beetle hunts with a pair of natural bifocal lenses.

The beetle relies on its keen eyesight to stalk other insect larvae amid often murky streams. It sees the world through no less than six pairs of eyes and in 2006, Elke Buschbeck discovered that each of these has at least two retinas. One of her students Annette Stowasser has focused on the front pair, and shown that they are unlike any other in the animal kingdom.