Add to that the "Black Friday" effect: fierce competition for limited supplies while they last.
"Imagine: As soon as the sun sets, all the hawkmoths fly around flower patches in the desert," von Arx said. "These flowers open within minutes of each other, and as soon as they do, the moths go there. A big flower patch or a plant with multiple flowers might attract many moths at the same time, so it's very important for an individual to pick the most profitable one very quickly."
The research group first measured humidity levels around a nectar-bearing flower by enclosing primrose plants in a sealed container and scanning the air inside with highly sensitive humidity measuring devices called hygrometers. They found that humidity just above the opening flower was slightly higher than ambient levels, caused partly by a plume of water vapor emanating from the flower's nectar tube.
To study whether and how moths respond to the humidity evaporating from nectar stores, the research team put artificial flowers to exclude any other potential signal other than humidity levels in a flight cage large enough for the moths to fly about freely.
Even though none of the artificial flowers had nectar, the moths would preferentially hover and extend their proboscis into those that had slightly elevated humidity compared with those that matched the humidity around them. The animals were able to sense if humidity near a flower was elevated as little as 4 percent above ambient humidity in the flight cage, despite of the turbulence generated by many moths hovering about.
"It was really exciting to see their high sensitivity to humidity in that they can perceive such a minute amount of difference in such a dynamic environment," von Arx said.
The results help researchers better understand the ecological relationships between flowers and their pollinators, especially in arid environments such as the
|Contact: Daniel Stolte|
University of Arizona