Floral CO2 emission may indicate food abundance to nectar-feeding moths

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Abstract
As part of a study of the roles of the sensory subsystem devoted to CO2 in the nectar-feeding moth Manduca sexta, we investigated CO2 release and nectar secretion by flowers of Datura wrightii, a preferred hostplant of Manduca. Datura flowers open at dusk and wilt by the following noon. During the first hours after dusk, when Manduca feeds, the flowers produce considerable amounts of nectar and emit levels of CO2 that should be detectable by moths nearby. By midnight, however, both nectar secretion and CO2 release decrease significantly. Because nectar production requires high metabolic activity, high floral CO2 emission may indicate food abundance to the moths. We suggest that hovering moths could use the florally emitted CO2 to help them assess the nectar content before attempting to feed in order to improve their foraging efficiency.