Acousti­cal Mim­icry

by Elio

We sel­dom stray from mi­cro­bial do­mains, but here is a stun­ning (and de­light­ful) rea­son for wan­der­ing fur­ther afield. Af­ter all, ex­am­ples of par­a­sitism are surely not con­fined to the Small Things and lessons can be learned wher­ever they ap­pear. Ac­cord­ing to a group of re­searchers from Eng­land and Italy, par­a­sites of some ants mimic the sounds made by the queen of a colony. The ants in ques­tion are a red Eu­ro­pean species, Myr­mica schencki. Their queens make dis­tinc­tive sounds by scrap­ing a plec­trum across a file, some­what like a wash­board player who makes mu­sic by scratch­ing his in­stru­ment. Worker ants use the same mech­a­nism to make their own re­frain, but they dif­fer enough mor­pho­log­i­cally from the queens that their in­stru­ments pro­duce a rec­og­niz­ably dif­fer­ent sound. (The ants can tell them apart. Can you? Click here to down­load au­dio clips.) Much like a Zy­deco player, the royal per­former makes sounds that "elicit benev­o­lent re­sponses from work­ers, re­in­forc­ing their supreme so­cial sta­tus." (Source) This be­hav­ior can be ob­served in the lab­o­ra­tory, us­ing ap­pro­pri­ate tapes and speak­ers.

Myr­mica schencki. Source

Like many good strate­gies that can ben­e­fit a species, there are par­a­sites that take ad­van­tage of this acousti­cal com­mu­ni­ca­tion sys­tem. Here, the op­por­tunist is an M. schencki-spe­cific par­a­sitic but­ter­fly, the Moun­tain al­con blue Ma­c­u­linea re­beli. Its last in­star lar­vae are car­ried into the nest by M. schencki work­ers, where, fed by the work­ers, they in­crease in mass fifty-fold and then pu­pate. Both the pu­pae and the lar­vae emit sounds that re­sem­ble those of the ant queens, guar­an­tee­ing them "high sta­tus within ant so­ci­eties." This sta­tus is not just cer­e­mo­nial cour­tesy. When food is scarce, the nurse worker ants serve up their own brood as food for the but­ter­fly lar­vae.

Ma­c­u­linea re­beli. Source

Acoustic mim­icry is just one way that these par­a­sites de­ceive their hosts. There is also chem­i­cal mim­icry at play. How­ever, to us, the use of sound for de­cep­tion in these an­i­mals is novel. And be­ware! Just who is pro­gram­ming your iPod?