Scent helps hawk moths find best-fitting flowers

JENA, Germany, May 18 (UPI) -- New research shows the hawk moth is attracted to the bouquet of the best-fitting flowers -- evidence of the power of the co-evolutionary process.

Charles Darwin long ago noticed that pollinators and nectar providers share a morphological congruity. The length of the hawk moth's proboscis, for example, is roughly the same length as its favorite flowers.

Researchers from the Max Planck Institute for Chemical Ecology found hawk moths, Manduca sexta, gain the highest metabolic boost when they visit the best-fitting flowers.

Researchers tracked the flower selection of several hawk moths in a wind tunnel, tallying their uptake of sugar from the nectar of various flowers. Scientists tracked the moths' expended calories by measuring the levels of carbon dioxide exhaled during flight.

A sophisticated tracking system allowed scientists to model the presence and concentration of odors inside the wind tunnel. The system revealed which flower scents the moths encountered first. Their experiments showed the moths responded most strongly when first encountering the smell of Nicotiana alata flowers -- a flower that fits the length of the moth's proboscis perfectly.

Visits to Nicotiana alata flowers always resulted in a net energy gain for the moths.

"We showed that Darwin's prediction that each flower has a pollinator with a proboscis fitting into the flower, in Manduca not only resulted in a very long tongue, but also in a preference for the odor of the fitting flower," lead researcher Markus Knaden explained in a news release. "And that this co-evolution is beneficial for the moth, as the moth gets the best energy gain from fitting flowers."

The new research was published this week in the journal Nature Communications.