Location: Chemistry ResearchTitle: Foraging behavior of the Blue Morpho and other tropical butterflies: The chemical and electrophysiological basis of olfactory preferences and the role of color Author
Submitted to: Psyche
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/18/2012
Publication Date: 4/10/2012
Citation: Sourakov, A., Duehl, A.J., Sourakov, A. 2012. Foraging behavior of the Blue Morpho and other tropical butterflies: The chemical and electrophysiological basis of olfactory preferences and the role of color. Psyche. 2012:1-10. Interpretive Summary: The visual and chemical cues that lead tropical butterflies to food sources were examined in this series of experiments. ARS scientists at the Center for Medical, Agricultural and Medical Entomology in Gainesville, FL along with collaborators from the McGuire Center collected, analyzed and conducted biological tests on fruit volatiles as potential attractants for butterflies. The research demonstrated that butterflies use different cues to find food according to where they live in the forest. Forest canopy butterflies that feed on flowers were strongly attracted to visual cues but also used odor cues to make feeding decisions, while butterflies that normally feed on the dark forest floor relied on odor cues alone. This illustrates how important an understanding of an insects natural feeding preferences is to determine what sorts of attractants would be useful in sampling efforts. We also examined the ways that butterflies perceived the chemical cues. Using electrophysiological techniques we determined that not only were chemicals detected in the antennae but also in the feet and mouthparts. The specific detected chemicals were related to fruit ripeness and fermentation. This research helps us better understand the interplay of visual and chemical cues in diverse tropical environments where both plant and insect diversity are high.
Technical Abstract: Inside a live butterfly exhibit housing a variety of tropical butterfly species under north-central Florida ambient conditions, we conducted bioassays to determine whether the presence of color would facilitate the location of attractants by the butterflies. In two separate bioassays, the baits (honey and fermented banana) were presented with and without color cues. It was found that color facilitated odor attraction in some butterflies that are known to feed on flowers: Pathenos silvia, Heraclides thoas, Dryas julia, and Idea leuconoe, but not in the exclusively fruit-feeding species, Morpho helenor. This demonstrates that species with different natural diets use different foraging cues. Volatiles from fermented banana were collected and analyzed and the electrophysiological responses to these volatiles were studied in M. helenor and another fruit feeding species, Caligo telamonius. Fifteen different chemicals (both fermentation products and fruit semiochemicals) were shown to be detected by butterflies. They were detected by sensory apparatus in the forelegs, mid-legs, proboscis, labial palpi, and antennae of Morpho helenor and Caligo telamonius during GC-EAD evaluation, with identical response patterns shown by both species. While the legs, proboscis and antennae showed similar sensitivity, reacting to 11 of the same chemicals, the labial palpi had a lower signal to noise ratio and responded strongly to seven chemicals, only three of which produced responses in other organs. The detected compounds, all esters, should be evaluated further to determine the specifics of fruit attraction for these species and to develop lures to sample them in the field.