180 lines
10 KiB
Plaintext
180 lines
10 KiB
Plaintext
ÜÜÜÜÜÜÜÜÜÜÜÜÜ ÜÜÜ ÜÜÜÜ
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ÜÛÛÛÛÛÛÛÛßÛßßßßßÛÛÜ ÜÜßßßßÜÜÜÜ ÜÛÜ ÜÛÛÛÛÛÛÛÛÜÜÜÜÜÛßß ßÛÛ
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ßÛÛÛÛÛÛÛÛÛÛÛÛÛÛÜ ßÛÛ ÜÛÛÛÜÛÛÜÜÜ ßÛÛÛÛÜ ßÛÛÛÛÛÛÛÜÛÛÜÜÜÛÛÝ Ûß
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ßßßÛÛÛÛÛÛÛÛÛÛÜ ÞÝ ÛÛÛÛÛÛÛÛÛÛÛßßÛÜÞÛÛÛ ÛÛÛÛÛÜ ßßÛÛÛÞß
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Mo.iMP ÜÛÛÜ ßÛÛÛÛÛÛÛÝÛ ÞÛÛÛÛÛÛÛÛÛ ÞÛÛÛÛ ÞÛÛÛÛÛÝ ßÛß
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ÜÛÛÛÛÛÛÛ ÛÛÛÛÛÛÛÛÝ ÞÛÛÛÛÛÛÛÛÝ ÛÛÛ ÛÛÛÛÛÛ
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ÜÛÛÛÛÛÛÛÝ ÞÛÛÛÛÛÛÛÛ ÞÛÛÛÛÛÛÛÛ ß ÞÛÛÛÛÛÛÜ ÜÛ
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ÜÛÛÛÛÛÛÛÝ ÛÛÛÛÛÛÛÛ ÛÛÛÛÛÛÛÛÝ ÞÞÛÛÛÛÛÛÛÛÛß
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ÜÛßÛÛÛÛÛÛ ÜÜ ÛÛÛÛÛÛÛÛÝ ÛÛÞÛÛÛÛÛÝ ÞÛÛÛÛÛÛßß
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ÜÛßÛÛÛÛÛÛÜÛÛÛÛÜÞÛÛÛÛÛÛÛÛ ÞÛ ßÛÛÛÛÛ Ü ÛÝÛÛÛÛÛ Ü
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ÜÛ ÞÛÛÛÛÛÛÛÛÛÛß ÛÛÛÛÛÛÛÛÛ ßÛÜ ßÛÛÛÜÜ ÜÜÛÛÛß ÞÛ ÞÛÛÛÝ ÜÜÛÛ
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ÛÛ ÛÛÛÛÛÛÛÛß ÛÛÛÛÛÛÛÛÛÛÜ ßÛÜ ßßÛÛÛÛÛÛÛÛÛß ÜÜÜß ÛÛÛÛÜÜÜÜÜÜÜÛÛÛÛÛß
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ßÛÜ ÜÛÛÛß ßÛÛÛÛÛÛÛÛÛÛÜ ßßÜÜ ßßÜÛÛßß ßÛÛÜ ßßßÛßÛÛÛÛÛÛÛßß
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ßßßßß ßßÛÛß ßßßßß ßßßßßßßßßßßßß
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ARRoGANT CoURiERS WiTH ESSaYS
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Grade Level: Type of Work Subject/Topic is on:
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[ ]6-8 [ ]Class Notes [Essay on Mimicry in ]
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[ ]9-10 [ ]Cliff Notes [Nature ]
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[x]11-12 [x]Essay/Report [ ]
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[ ]College [ ]Misc [ ]
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Dizzed: 11/94 # of Words:1439 School: ? State: ?
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ÄÄÄÄÄÄÄÄÄ>ÄÄÄÄÄÄÄÄÄ>ÄÄÄÄÄÄÄÄÄ>Chop Here>ÄÄÄÄÄÄÄÄÄ>ÄÄÄÄÄÄÄÄÄ>ÄÄÄÄÄÄÄÄÄ>ÄÄÄÄÄÄÄÄÄ
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THE GREAT IMPOSTERS
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Finding good day care can certainly pose a problem these days, unless,
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of course, you're an African widow bird. When it comes time for a female
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widow bird to lay her eggs, she simply locates the nest of a nearby
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Estrildid finch and surreptitiously drops the eggs inside.
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That's the last the widow bird ever sees of her offspring. But not to
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worry, because the Estrildid finch will take devoted care of the abandoned
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birds as if they were her own.
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And who's to tell the difference? Though adult widow birds and
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Estrildid finches don't look at all alike, their eggs do. Not only that,
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baby widow birds are dead ringers for Estrildid finch chicks, both having
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the same colouration and markings. They even act and sound the same, thus
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ensuring that the widow bird nestlings can grow up among their alien
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nestmates with no risk of being rejected by their foster parents.
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MASTERS OF DISGUISE
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Things aren't always as they seem, and nowhere is this more true than
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in nature, where dozens of animals (and plants) spend their time
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masquerading as others. So clever are their disguises that you've probably
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never known you were being fooled by spiders impersonating ants, squirrels
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that look like shrews, worms copying sea anemones, and roaches imitating
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ladybugs. There are even animals that look like themselves, which can also
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be a form of impersonation.
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The phenomenon of mimicry, as it's called by biologists, was first
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noted in the mid-1800s by an English naturalist, Henry W. Bates. Watching
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butterflies in the forests of Brazil, Bates discovered that many members of
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the Peridae butterfly family did not look anything like their closest
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relatives. Instead they bore a striking resemblance to members of the
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Heliconiidae butterfly family.
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Upon closer inspection, Bates found that there was a major advantage
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in mimicking the Heliconiids. Fragile, slow-moving and brightly coloured,
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the Heliconiids are ideal targets for insectivorous birds. Yet, birds
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never touch them because they taste so bad.
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Imagine that you're a delicious morsel of butterfly. Wouldn't it be
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smart to mimic the appearance of an unpalatable Heliconiid so that no bird
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would bother you either? That's what Bates concluded was happening in the
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Brazilian jungle among the Pieridae. Today, the imitation of an inedible
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species by an edible one is called Batesian mimicry.
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Since Bates' time, scientists have unmasked hundreds of cases of
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mimicry in nature. It hasn't always been an easy job, either, as when an
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animal mimics not one, but several other species. In one species of
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butterfly common in India and Sri Lanka, the female appears in no less than
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three versions. One type resembles the male while the others resemble two
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entirely different species of inedible butterflies.
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Butterflies don't "choose" to mimic other butterflies in the same way
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that you might pick out a costume for a masquerade ball. True, some
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animals, such as the chameleon, do possess the ability to change body
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colour and blend in the with their surroundings. But most mimicry arises
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through evolutionary change. A mutant appears with characteristics similar
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to that of a better protected animal. This extra protection offers the
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mutant the opportunity to reproduce unharmed, and eventually flourish
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alongside the original.
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In the world of mimics, the ant is another frequently copied animal,
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though not so much by other ants as by other insects and even spiders.
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Stoop down to inspect an ant colony, and chances are you'll find a few
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interlopers that aren't really ants at all but copycat spiders (or wasps or
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flies). One way you might distinguish between host and guest is by counting
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legs: Ants have six legs while spiders have eight. Look carefully and you
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might see a few spiders running around on six legs while holding their
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other two out front like ant feelers. COPYCATS
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Mimicry can not only be a matter of looking alike, it can also involve
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acting the same. In the Philippine jungle there is a nasty little bug, the
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bombardier beetle. When threatened by a predator, it sticks its back end in
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the air, like a souped-up sports car, and lets out a blast of poisonous
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fluid. In the same jungle lives a cricket that is a living xerox of the
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bombardier beetle. When approached by a predator, the cricket will also
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prop up its behind -- a tactic sufficient to scare off the enemy, even
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though no toxic liquid squirts out.
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Going one step further than that is a native of the United States, the
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longicorn beetle, which resembles the unappetizing soft-shelled beetle.
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Not content to merely look alike, the longicorn beetle will sometimes
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attack a soft-shelled beetle and devour part of its insides. By ingesting
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the soft-shelled beetle's bad-tasting body fluid, the longicorn beetle
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gives itself a terrible taste, too!
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Protection is by no means the only advantage that mimicry offers.
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Foster care can be another reward, as proven by the African widow bird. And
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then there's the old wolf-in-sheep's-clothing trick, which biologists call
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aggressive mimicry.
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The master practitioner of aggressive mimicry is the ocean-going
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anglerfish. Looking like a stone overgrown with algae, the anglerfish
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disguises itself among the rocks and slime on the ocean bottom. Protruding
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from its mouth is a small appendage, or lure, with all the features of a
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fat, juicy pink worm.
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The anglerfish lacks powerful teeth so it can't take a tight grip on
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its prey. Instead, it waits motionless until a small fish shows interest in
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the lure, and then wiggles the lure in front of the fish's mouth. When the
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small fish is just about to snap at the lure, the angler swallows
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violently, sucking the fish down its hatch. Diner instantly becomes dinner.
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SEXUAL IMITATORS
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Of all the many impostures found in nature, probably the sneakiest are
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those of the sexual mimics: males who imitate females to gain an advantage
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at mating time. Here in Ontario we have a sexual mimic, the bluegill fish.
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Male bluegills come in two types: the standard male and the satellite male,
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which looks just like a female bluegill.
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In preparation for mating, the standard male bluegill performs the
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job of building the nest, where he bides his time until a female enters it
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to spawn. Satellite fish don't build nests, choosing instead to hover
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around the nest of a standard male until the moment when a pregnant female
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enters. The satellite fish follows her into the nest, deceiving the
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nestbuilder into believing that he is now in the presence of two females.
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The three fish swim around together, and when the female drops her eggs,
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both males release a cloud of sperm. Some of the eggs are fertilized by the
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resident male, some by the satellite male, thus passing on passing on
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different sets of male genes to a new generation of bluegills.
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Another case of sexual mimicry has recently been uncovered in Manitoba
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among the red-sided garter snakes. The little town of Inwood, Manitoba and
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the surrounding countryside is garter snake heaven, where you can find the
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largest snake colonies on Earth.
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Every spring, the red-sided garter snake engages in a curious mating
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ritual. Soon after spring thaw, the males emerge first from their winter
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cave and hover nearby. The females then slither out a few at a time, each
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one exuding a special "perfume" which signals to the fellows that she's
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ready to mate. At first whiff of this lovely odour, a mass of frenetic
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males immediately besieges the female, wrapping her up in a "mating ball"
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of 10, 20 or sometimes as many as 100 writhing males, all hoping to get
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lucky.
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Scientists have now discovered that some male red-sided garters give
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off the same perfume as the female, and they do this while intertwined in
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the mating ball. Male and female red-sided garters look exactly alike, so
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the male with the female scent can effectively distract many of the males
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from the real female, giving the imposter a better shot at getting close to
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the female and impregnating her.
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Males passing as females, fish as bait, beetles as ants -- amidst all
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this confusion, it still sometimes pays to just be yourself, which could
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certainly be the motto of the amazing hair-streak butterfly family.
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Decorating the hair-streak's lower hind wings are spots that look like
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eyes, and out-growths that look like antennae, creating the illusion that
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the butterfly has a second head. Whenever the hair-streak alights, it
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jerks its dummy antennae up and down while keeping its real antennae
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immobile. Presumably, this dummy head exists to distract predators. If so,
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we finally have the first scientific proof that two heads are better than
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one.
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