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 These moths, whose olfactory abilities are as good as a
bloodhound's and vastly better than a human's, can fly up to 80
miles (130 km) a night searching for their favorite flowers such as
the Sacred Datura.
The nectar of these fragrant white, trumpet-shaped flowers that
bloom only once at night is an important food source for the moths,
which pollinate the flowers. Females also go to the flowers to lay
eggs. After hatching, the larvae eat the plant's leaves.
Scientists have wondered how pollinating insects such as these moths
track down the flowers they need and whether competing odors -
natural and manmade - can mess things up.
In a study published on Friday in the journal Science, researchers
placed the moths in a laboratory wind tunnel and exposed them to an
array of odors such as car and truck exhaust fumes and fragrances of
other plants.
Human sources of pollution fouled up their ability to find flowers
and changed how the flower's scent was processed by olfactory
neurons in the moth's brain.
"Pollinators like bees, butterflies and moths use their sense of
smell to locate flowers from long distances, but we found that scent
from neighboring vegetation, and even pollutants given off from
vehicle exhaust, can disrupt the moth's behavior," University of
Washington biology professor Jeffrey Riffell said.
"Now for the moths that are flying long distances, they can't
adequately smell the flowers and at times won't even know the
flowers are there," Riffell added. "We really need to conduct more
experiments to find out if these pollutants, or even certain plants,
might similarly disrupt other pollinators, like honeybees, that are
agriculturally important."
The tobacco hornworm moth - a large, nocturnal insect with a
wingspan of about 4 inches (10 cm) - ranges from Canada to Central
America, including across the United States. In the U.S. Southwest,
their favored flower is the Sacred Datura, also known as angel's
trumpets.
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In a wind tunnel and a computer-controlled odor-stimulus system, the
moths were tested to see how well they could distinguish different
intensities of Sacred Datura fragrance, as well as mixes of
background odors from other plants such as the creosote bushes that
often grow nearby. The researchers also piped in chemicals such as
those emitted in vehicle exhaust.
The researchers tracked the neuron pathways activated by placing an
electrode into the moth's antennal lobe. The antennae serve as an
insect's nose. The antennal lobe is the part of the brain that
processes odors from the antennae.
The moths can zero in on flowers hundreds of yards (meters) away if
there are not too many competing odors. Such odors mess with the
balance of excitation and inhibition in the olfactory system,
keeping the moths from recognizing the flowers.
"The total combination of dynamic odors, including floral signature
odors as well as anthropogenic pollutants, can affect the success of
olfactory-based resource finding," University of Arizona researcher
Leif Abrell added.
(Reporting by Will Dunham. Editing by Andre Grenon)
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