Non-floral scent sources of orchid bees: observations and significance

Males of the neotropical orchid bees collect environmental volatiles to concoct complex species-specific perfumes that are later used in sexual communication. While perfumes are typically seen as being derived from floral sources, these bees also collect scents from non-floral resources such as decaying wood or tree wounds, even though reports of these sources remain scarce. Here we report observations of male orchid bees collecting scent at 21 different non-floral sources in Central and South America. Male Eufriesea corusca that were marked at one of them, a wounded Protium ravenii secreting odoriferous sap/resin, returned repeatedly over periods of up to 19 days. Chemical analyses of hind-leg contents suggest that this single non-floral source accounted for a substantial fraction (>50%) of the species-specific perfume. This and other findings strengthen the view that non-floral scent sources play a central role in orchid bee perfume biology. Moreover, at the same Protium we also observed female Euglossa spp. harvesting resin for nest construction. The collection of substances by both euglossine male and female bees at the same source strengthens the notion that the evolution of male perfume signaling was promoted by a sensory bias for resinous nest construction materials in females.