MARKWELL, Poppy*; GOYRET, Joaquin; RAGUSO, Robert A.; Oberlin College; Univ. of S. Carolina, Columbia; Univ. of S. Carolina, Columbia: Decoupling odor from visual cues in nectar feeding by Manduca sexta

Nocturnal hawkmoths (Lepidoptera, Sphingidae) are innately attracted to flowers that provide a combination of visual and olfactory cues. One species, Manduca sexta, approaches flowers when these sensory cues are physically decoupled, but only feeds when visual and olfactory cues are combined. This observation suggests a neural basis for the integration of cross-modal stimuli relevant to nectar foraging. Here, we tested whether M. sexta will feed from artificial flowers when visual and olfactory stimuli are spatially decoupled in a laminar flow wind tunnel. Specifically, we tested whether different degrees of physical separation between a white artificial flower and an odor plume were equally sufficient in triggering the appetitive response in M. sexta moths. Na�ve, laboratory reared M. sexta were flown upwind to seven treatments and controls with different combinations of visual and olfactory cues. There were no differences in moths� responses to treatments in which flower and odor source were separated by 0, 10 or 20 cm. Plume visualization with titanium chloride smoke revealed that this range encompassed the physical distribution of the odor plume. However, beyond 20 cm of separation between stimuli, feeding response diminished significantly; the stimuli were no longer recognized as a multi-modal feeding cue. These results are consistent with our previous experiments in flight cages and natural populations, suggesting that flower feeding by M. sexta is an emergent property released by combined olfactory and visual stimuli, regardless of whether odor is a plume or a cloud, or whether visual display is a single flower or an array.