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This Assassin Only Kills If Its Victim Strikes First

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Letting your opponent land the first blow usually isn’t a surefire strategy for winning a fight, but for one insect predator, it’s the only way to come out on top.

As their name might suggest, assassin bugs are formidable killers. They’ve got a long proboscis that they use to stab prey, inject a tissue-liquefying toxic saliva and suck the pre-digested innards out for consumption. It’s like a harpoon, syringe, and straw all in one. 

When brute strength and poison aren’t enough to make the kill or get out of trouble with their own predators, the bugs have a few other tricks. One species wears its victims’ flesh as a disguise. When it’s finished with its meals, the assassin tosses the drained carcasses onto its sticky back, building a cloak of corpses that disguises the bug and protects it from spiders. 

Another species hunts spiders instead of hiding from them, and plucks the strands of their webs to mimic the vibrations of struggling prey. When the spider rushes over expecting a meal—Pow! Toxic proboscis sneak attack!—it becomes one instead. 

Scientists have just discovered a different sort of tactic used by the species Ptilocnemus lemur, which hunts ants. It also deceives its quarry, but uses one of its own legs as a lure and lets an ant attack it before going in for the kill.

The assassin bug begins by waving one of its bristly hind legs around to attract nearby ants. Unlike all the other lurer hunters that the researchers know of, the assassin doesn’t strike when an ant gets within range, or even when it touches or grasps the bait. It just waits.

Finally, when—and only when—the ant firmly grips the bug’s leg and either attempts to sting it or drag it away, the assassin leaps into action. With the ant still hanging on to its leg, P. lemur lifts itself up and swivels 180 degrees on its “knee” joint. Now its body is above the ant, and perfectly positioned to attack a weak point in the prey’s hardened exoskeleton—a soft membrane between the head and thorax. 

Proboscis goes in. Nutritious goo comes out. 

As the researchers, led by Australian ecologist Matthew Bulbert, watched, the assassins successfully killed 81 percent of the ants that fell for their trick. In almost 500 of these attacks, though, not one assassin bug died. 

Ants are dangerous game and adept insect killers themselves. Some species are also several times bigger than the assassin bugs. Using its own leg as bait with them would seem to put the assassin in harm’s way, but Bulbert and his team think the seemingly risky strategy of letting the ant bite first actually reduces the bug's chances of getting hurt. 

By presenting its leg and waiting until the ant latches on, the assassin has tricked the ant into concentrating all its offensive traits—its size, its jaws and its venom—onto one body part. Once the ant attempts to claim its meal, its entire arsenal is occupied, and it's unable to defend itself from an quick counter-attack that comes from above and behind its head. By taking a blow to the leg, the assassin bug turns the hunter into the hunted “unopposed and essentially risk free,” the researchers say. 

Crafty and effective as it is, the strategy also has some constraints. Only 2.5 percent of the ants that the researchers saw actually grabbed the assassin bugs’ legs. But the slim chance of an ant falling for the trick, Bulbert thinks, is offset by their size. The average ant that the assassins preyed on was one to two times larger than its killers, and could feasibly provide enough food to keep an assassin going through some lean times. In some cases, the ants were as much as five times bigger than the assassin, and the bug lost all contact with the ground when it flipped over on top of its prey and had to ride on the ant’s back until it died. 

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Big Questions
Why Do Cats Love Scratching Furniture?
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Allergy suffering aside, cat ownership has proven health benefits. A feline friend can aid in the grieving process, reduce anxiety, and offer companionship.

The con in the cat column? They have no reservations about turning your furniture into shredded pleather. No matter how expensive your living room set, these furry troublemakers will treat it with the respect accorded to a college futon. Do cats do this out of some kind of spite? Are they conspiring with Raymour & Flanigan to get you to keep updating home decor?

Neither. According to cat behaviorists, cats gravitate toward scratching furniture mostly because that love seat is in a really conspicuous area [PDF]. As a result, cats want to send a message to any other animal that may happen by: namely, that this plush seating belongs to the cat who marked it. Scratching provides both visual evidence (claw marks) as well as a scent marker. Cat paws have scent glands that can leave smells that are detectable to other cats and animals.

But it’s not just territorial: Cats also scratch to remove sloughed-off nail tips, allowing fresh nail growth to occur. And they can work out their knotted back muscles—cramped from sleeping 16 hours a day, no doubt—by kneading the soft foam of a sectional.

If you want to dissuade your cat from such behavior, purchasing a scratching post is a good start. Make sure it’s non-carpeted—their nails can get caught on the fibers—and tall enough to allow for a good stretch. Most importantly, put it near furniture so cats can mark their hangout in high-traffic areas. A good post might be a little more expensive, but will likely result in fewer trips to Ethan Allen.

Have you got a Big Question you'd like us to answer? If so, let us know by emailing us at bigquestions@mentalfloss.com.

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Animals
7 Fun Facts for Elephant Appreciation Day
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Happy Elephant Appreciation Day! Celebrate the occasion with some facts about everyone's favorite gentle giant. 

1. ELEPHANTS CAN RECOGNIZE OTHER ELEPHANT CARCASSES.

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The University of Sussex's Karen McComb told National Geographic that elephants "become excited and agitated if they come across a dead elephant," and, in particular, will investigate skulls and tusks. McComb teamed up with researchers at the Amboseli Elephant Research Project in Kenya to study the behavior, showing wild elephants a range of objects that included skulls. They found that the elephants examined skulls—and tusks in particular—of their own kind twice as long as other skulls, and examined tusks six times as long as they did pieces of wood. They were even able to recognize elephant skulls with the tusks removed, but didn't show preference for certain elephant skulls over others, which suggests they didn't know which skulls belonged to their own relatives. "Animals that are intensely social in life may be most likely to display an interest in their dead," McComb told National Geographic. "But what goes on in their minds while they are doing this is a total mystery."

2. THEY'RE SCARED OF BEES.

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Forget about mice scaring off elephants: When farmers need to keep elephants away from their crops, they should use bees. Researchers in Kenya discovered that even the recorded sound of buzzing bees was enough to make elephants retreat—and cause them to emit a low-frequency sound, inaudible to humans, that warns other elephants of the bees' presence.

"It's impossible to cover Africa in electric fences," Lucy King, author of the paper, told The Huffington Post. "The infrastructure doesn't exist in many places and it would restrict animals' movement." But something like a bee fence—hives strung on strong wires a certain distance apart that would move when elephants walked into them, disturbing the hives—"could be a better way to direct elephants away from farmers' crops," she said.

3. THEY MIGHT UNDERSTAND POINTING.

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Humans often use pointing as a way to nonverbally get a message across, though not many other animals grasp the concept. But according to a two-month study of 11 tame African elephants, these pachyderms might be able to: When presented with two identical buckets and pointed in the direction of the one containing food, elephants picked up on the cue fairly consistently: Elephants had a success rate of 67.5 percent (1-year-old humans have a success rate of 72.7 percent). But an earlier study of Asian elephants indicated that they don’t notice pointing gestures, which is a bit of a mystery.

4. ONE ELEPHANT CAN "TALK." 

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Koshik, an elephant in a South Korean zoo, developed the ability to imitate the sounds of five words he's heard from his trainer—annyeong (hello), anja (sit down), aniya (no), nuwo (lie down), and joa (good)—by sticking his trunk in his mouth. The scientists who first noticed Koshik’s ability speculate that he learned to “talk” because he was lonely.

5. THEY'RE DIGITIGRADES.

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It's Latin for "finger walking," and what it means is that elephants walk on their toes (there are five of them, as well a sixth false toe). According to the book Mammal Anatomy: An Illustrated Guidemost of the animals' weight "rests on a broad pad of elastic tissue behind the toes" which "acts as a shock absorber and prevents the skeleton from jolting too much when the animals walk. It also allows elephants to move surprisingly quietly despite their size."

6. AN ELEPHANT PREGNANCY LASTS ABOUT TWO YEARS.

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If you thought being pregnant for nine months was a long time, be glad you're not an elephant, which can be pregnant for up to 680 days, according to the BBC. All that time in the oven has a benefit, though: Elephant calves are born with highly-developed brains, capable of learning their herd's complex social structures and ready to put their trunks to use.

7. NINETY-SIX ELEPHANTS ARE KILLED IN AFRICA EVERY DAY.

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Unfortunately, elephant poaching remains a very big problem: An estimated 35,000 elephants are killed annually, their tusks sold illegally in the ivory market. Do the math, and that comes out to nearly 96 elephants every day. Find out what you can do to help elephants and stop poaching at 96Elephants.org.

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