University of Florida lepidopterist Andrei Sourakov has spent his life's work studying moths and butterflies. But it was his teenage daughter, Alexandra, who led research on how color impacts butterflies' feeding patterns.
The research shows different species exhibit unique foraging behaviors, and the study may be used to build more effective, species-specific synthetic lures for understanding pollinators, insects on which humans depend for sustaining many crops.
In a study appearing online in April in the journal Psyche: A Journal of Entomology, researchers used multi-colored landing pads and baits in the Florida Museum of Natural History's McGuire Center for Lepidoptera and Biodiversity on the UF campus to determine that some butterflies use both sight and smell to locate food, while others rely primarily on smell.
"Butterflies are a great model for studying the environment and we can move in different directions from here in terms of application," said Florida Museum collection coordinator and study co-author Andrei Sourakov. "We've shown choosing certain scents or colored plants might depend on what species you want to attract -- if we can determine how to attract butterflies, perhaps we can also trap pest moths that lay eggs in agricultural fields."
Alexandra Sourakov began the research for a local science fair competition in 2009, spending weekends and after-school hours conducting experiments in the Florida Museum's Butterfly Rainforest exhibit.
"In eighth grade, we had to design a project, and I spend a lot of time around butterflies because my dad works with them," said Eastside High School sophomore Alexandra. "I've always been curious how they were able to locate their food, whether they fed on flowers or fruit, and so I started looking at it in the Butterfly Rainforest."
Alexandra placed red, yellow and black cardboard landing pads covered with honey, and observed flower-feeding species had a greater preference for the red color. But the exclusively fruit-feeding Blue Morpho showed no preference for a particular color. Mango, honey and green, ripe and fermented bananas were presented to fruit-feeding butterflies, and fermented bananas proved most attractive.
After winning first prize in eighth grade at the state science fair, Alexandra Sourakov was invited by study co-author and science fair judge Adrian Duehl to expand her study and conduct chemical analysis at the U.S. Department of Agriculture on UF's campus.
"Of about 600 butterflies attracted to bait, half of them were the Blue Morphos, so it was a logical species to focus on for the chemical part of the study," Andrei Sourakov said.
Gas chromatography coupled with parallel detection by mass spectrometry and electroantennography (measuring antennae output to the brain) were used to determine which chemicals that smelled like fermented bananas cause reactions in the Blue Morpho butterflies' body parts, including antennae, proboscis, legs and labial palpi, which are small projections protruding from the head. Surprisingly, all the organs reacted to the same range of chemicals except the labial palpi.
"It might have been expected that the results were species-specific because each species feeds on different food, but I was surprised by the results from the body parts because I wasn't even sure if any of them except the antennae would react to the volatile chemicals," Alexandra Sourakov said. "That was interesting because it shows a joint message may be sent to the brain from these different organs. This expands our understanding of butterflies' sense of smell."
Little is known about the function of the labial palpi and their contrasting reaction to the chemicals poses new questions about how different organs are used in finding food, said Adriana Briscoe, an associate professor in the department of ecology and evolutionary biology at the University of California Irvine who studies how color vision affects foraging behavior in butterflies.
"What's nice about this study is that it's multi-disciplinary, in that it looks at both vision behavior and olfactory behavior and physiology," Briscoe said. "It's very interesting that they found the different compounds in fruit are sensed by different body parts of the butterfly and it suggests that different organs are specialized for detecting different compounds."
Andrei Sourakov initiated the study as a means to involve young people in research and Briscoe agrees that, "the more young kids or high school kids that can get involved in doing science, the better off we are as a society."
"I would love to see more of this sort of thing done," Briscoe said. "It's challenging to engage high school students with science, and I think butterflies are a wonderful way to draw them in."
- Alexandra Sourakov, Adrian Duehl, Andrei Sourakov. Foraging Behavior of the Blue Morpho and Other Tropical Butterflies: The Chemical and Electrophysiological Basis of Olfactory Preferences and the Role of Color. Psyche: A Journal of Entomology, 2012; 2012: 1 DOI: 10.1155/2012/378050
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