A Social Parasite’s Sophisticated Mimicry
甲蟲寄生蟻穴 善於模仿
By Carl Zimmer

An ant colony is an insect fortress: When enemies invade, soldier ants quickly detect the incursion and rip their foes apart.
一個螞蟻聚落就是一座昆蟲要塞：每當有敵人來犯，兵蟻會迅速察覺，並且把敵人碎屍萬段。

But some invaders manage to slip in with ease, none more mystifyingly than the ant nest beetle.
然而有些入侵者卻有辦法毫不費力地混入，而這些入侵者當中沒有比喜蟻性粗角步行蟲更懂得欺敵的了。

Adult beetles stride into an ant colony in search of a mate, without being harassed. They lay eggs, from which larva hatch. And, it seems, workers feed the young beetles as if they were ants.
成年甲蟲在不受騷擾的情況下跨進螞蟻巢穴，尋找交配的對象。牠們產卵，卵再孵化為幼蟲。看起來，工蟻把這些甲蟲的幼蟲當成螞蟻般餵食。

When the beetles become adults, the ants swarm around them, grooming their bodies. But then the beetles sink their jaws into ant larvae and freshly moulted adults to drink their body fluids.
當甲蟲長大為成蟲時，螞蟻圍繞牠們爬行，為甲蟲梳理。但是甲蟲卻把下顎沉入螞蟻的幼蟲和剛變為成蟲的螞蟻體內，啜飲牠們的體液。

“They’re like vampire beetles,” said Andrea Di Giulio of Roma Tre University in Rome.
羅馬第三大學的安德烈．迪朱里歐說：「牠們就像吸血鬼甲蟲。」

Dr. Di Giulio and others have now discovered the beetles can perform uncanny impressions, mimicking a range of ant calls.
迪朱里歐博士和一些其他人現在發現，這些甲蟲能表現出可怕的印象，模仿螞蟻的多種聲音。

He and his colleagues study a species of ant nest beetle called Paussus favieri, which lives in the Atlas Mountains of Morocco, where it infiltrates the nests of Moroccan ants, known as Pheidole pallidula.
他和同事研究一種叫做投彈手甲蟲（Paussus favieri）的步行蟲，這種甲蟲分布於摩洛哥的阿特拉斯山脈，牠們會滲透到也稱作義大利家蟻的一種摩洛哥螞蟻（Pheidole pallidula）的巢穴裡。

Like many ant species, Pheidole pallidula makes noises by rubbing its legs against ridges on its body. The meanings of these signals vary from species to species; leaf-cutting ants summon bodyguards to return to the nest; in other species, a queen trills to her workers to attend to her. Scientists say Pheidole pallidula ants make three distinct sounds, each by a different caste: soldiers, workers and the queen.
如同許多種類的螞蟻，義大利家蟻藉由用腳摩擦背脊發出聲音，這些信號的意義隨著螞蟻種類而有不同。切葉蟻用來召喚保鑣回巢，其他種類則有蟻后發出顫音，把工蟻叫到身邊。科學家說，義大利家蟻發出三種明顯不同的聲音，各由不同階級的螞蟻製造：兵蟻、工蟻和蟻后。

Dr. Di Giulio and his colleagues noticed Paussus favieri, also have ridges, suggesting that they too can make sounds. But related beetles that don’t invade ant nests don’t have this kind of anatomy. So the scientists set the beetles on microphones and listened carefully. The beetles began to sing. They made three sounds, each closely resembling the one made by a different ant caste. “We were stunned by finding such a complex pattern of signals,” Dr. Di Giulio said.
迪朱里歐及同事們注意到，投彈手甲蟲也有背脊，推斷牠們也能發出聲音。但是其他不會入侵蟻穴的同類甲蟲，就沒有這種構造。所以科學家把這種甲蟲放在麥克風上聆聽，甲蟲開始發出聲音。牠們發出三種聲音，每一種都很接近不同階級螞蟻所製造的聲音。迪朱里歐博士說：「發現如此複雜的信號形式讓我們相當震驚。」

He wondered if the beetles were mimicking the ants in order to trick them. They installed a miniature loudspeaker in a chamber and buried it in sand, then put ants in the chamber and played beetle calls through the speaker.
他想要知道，甲蟲模仿螞蟻的聲音，是否為了欺騙。他們在一個箱子內裝設迷你擴音器並用沙埋住，然後把螞蟻置入箱內，再透過擴音器向箱內播放甲蟲的聲音。

The ants crawled toward the sound to investigate, waving their antenna in a pattern they use only to detect fellow ants. Then “they started digging to the speaker, like they were rescuing somebody,” said Dr. Di Giulio.
螞蟻爬向聲音來源以一探究竟，以只有在尋找同伴時才會使用的方式搖動牠們的觸鬚。迪朱里歐說，接著「牠們開始朝著擴音器挖掘，像是要救什麼同伴似的」。

The scientists published their findings in July in the journal PLOS One.
這幾位科學家把他們的發現發表於七月號的「公共科學圖書館期刊」。

Scientists refer to ant nest beetles as social parasites. Instead of infecting a single host’s body, they hijack an entire society.
科學家把步行蟲稱為社會性寄生蟲，牠們不是感染單一宿主的身體，而是劫持整個社群。

Dr. Di Giulio said the new findings demonstrate just how impressive parasites can be.
迪朱里歐說，這項新發現顯示寄生蟲可以如此令人印象深刻。

“The parasite is actually more complex than related beetles that are not parasites,” he said.
他說：「這種寄生蟲實際上比不是寄生蟲的同類甲蟲更來得複雜。」

原文參照：
http://www.nytimes.com/2015/07/21/science/ant-nest-beetles-social-parasites-mimicry.html

2015-08-18聯合報/G5版/UNITED DAILY NEWS 莊蕙嘉譯 原文參見紐時週報十版下