NightoftheLivingAnts

　　Whenanantdies,otherantsmovethedeadinsectoutofthenest.Thisbehaviorisinterestingtoscientists,whowonderhowantsknowforsure-andsosoon-thatanotherantisdead.

　　Dong-HwanChoe,ascientistattheUniversityofCaliforniafoundthatArgentineantshaveachemicalontheoutsideoftheirbodiesthatsignalstootherants,"I'mdead-takemeaway."

　　Butthere'satwisttoChoe'sdiscovery.Theseantsarealittlebitlikezombies.Choesaysthatthelivingants-notjustthedeadones-havethisdeathchemical.Inotherwords,whileanantcrawlsaround,perhapsinapicnicorhome,it'stellingotherantsthatit'sdead.

　　Whatkeepsantsfromhaulingawaythelivingdead?ChoefoundthatArgentineantshavetwoadditionalchemicalsontheirbodies,andthesetellnearbyantssomethinglike,"wait-I'mnotdeadyet."SoChoe'sresearchturneduptwosetsofchemicalsignalsinants:onesays,"I'mdead,"theothersetsays,"I'mnotdeadyet."

　　Otherscientistshavetriedtofigureouthowantsknowwhenanotherantisdead.Ifanantisknockedunconscious,otherantsleaveitaloneuntilitwakesup.Thatmeansantsknowthatunmovingantscanstillbealive.

　　ChoesuspectsthatwhenanArgentineantdies,thechemicalthatsays"Wait-I'mnotdeadyet"quicklygoesaway.Oncethatchemicalisgone,onlytheonethatsays"I'mdead"isleft."It'sbecausethedeadantnolongersmellslikealivingantthatitgetscardedtothegraveyard,notbecauseitsbodyreleasesnewuniquechemicalsafterdeath,"saidChoe.Whenotherantsdetectthe"dead"chemicalwithoutthe"notdeadyet"chemical,theyhaulawaythebody.ThiswasChoe'shypothesis.

　　Totesthishypothesis,ChoeandhisteamputdifferentchemicalsonArgentineantpupae.Whenthescientistsusedthe"I'mdead"chemical,otherantsquicklyhauledthetreatedpupae7away.Whenthescientistsusedthe"Wait-I'mnotdeadyet"chemicals,otherantsleftthetreatedpupaealone.Choebelievesthisbehaviorshowsthatthe"notdeadyet"chemicalsoverridethe"dead"chemicalwhenpickedupbyadultants.Andthatwhenanantdies,the"notdeadyet"chemicalsfadeaway.Othernearbyantsthendetecttheremaining"dead"chemicalandremovethebodyfromthenest.