Curr. Biol. http://doi.org/brnh (2016)
Many plants release volatile signals to attract insect pollinators, while other plants employ floral mimicry to the same end. Stefan Dötterl of the University of Salzburg, Austria, and colleagues have identified an example of a plant that combines the two, producing a ‘dishonest’ volatile mixture to attract a similarly underhand fly.
Ceropegia sandersonii, commonly known as the parachute or umbrella plant, is a native of southern Africa. The researchers identified the principle pollinators of C. sandersonii to be flies of the genus Desmometopa, which are trapped by the plant's inverted-funnel-shaped flowers and covered in pollen before being released when the flowers die. Desmometopa flies feed on the captured prey of predatory arthropods such as spiders. Dötterl and colleagues found that the volatiles released from C. sandersonii flowers were ∼60% similar to those given off by captured and stressed honeybees.
Electrophysiology showed that the antennae of female Desmometopa responded to volatiles from both C. sandersonii and the attacked honeybees. Furthermore, mixtures of their major components — geraniol, 2-heptanone, 2-nonanol and (E)-2-octen-1-yl acetate — rapidly attracted Desmometopa. The composition of the floral scent of C. sandersonii contains several compounds, such as (E)-2-octen-1-yl acetate, not seen in other flowers; a specialized bait for a specialized quarry.