How mimicking a bee under attack can attract pollinators

Many species rely on a little chemical con artistry for survival, but an international research team has uncovered a particularly crafty sting involving deceitful plants, kleptoparasitic flies, and honeybees. In this ruse, the hustler is the South African parachute plant Ceropegia sandersonii and its mark is Desmometopa—the so-called freeloader fly—the plant’s primary pollinator. To lure in the flies, the plant appears to chemically mimic a staple of the Desmometopa diet: honeybees captured by spiders and other predators (Curr. Biol. 2016, DOI: 10.1016/​j.cub.2016.07.085). As honeybees attempt to fend off their attackers, they secrete a cornucopia of volatile compounds from their stingers and glands, which theflies interpret as an invitation to dinner. Using GC/MS, researchers led by Stefan Dötterl of the University of Salzburg and Annemarie Heiduk of the University of Bayreuth found that 60% of the compounds emitted by distressed honeybees are also emitted by the plant. Furthermore, Desmometopa flies were attracted to a lab-made cocktail containing a select few of these chemicals, notably geraniol, 2-nonanol, 2-heptanone, and (E)-2-octen-1-yl acetate. C. sandersonii and honeybees are the only plant and animals known to emit these four compounds in concert, the team says.