Orchid bees collect species-specific scent bouquet
Scientists at the Heinrich Heine University in Düsseldorf led by Thomas Eltz and Klaus Lunau have examined the odor biology of three Central American orchid bee species (Euglossini) and found something amazing: Chemical analyzes of the odor sacs showed that the odor bouquet of individual males consists of up to fifty components exists and has a different composition depending on the species. In order to put together this mixture of scents, the males have to spend many weeks collecting scents from very different sources.
What was particularly amazing was that conspecifics from very different areas of Panama and Costa Rica managed to arrive at the same species-specific perfume despite different scent sources. Experiments with males in flight cages showed that this ability relies on avoidance of components already collected, compensating for local differences in supply.
Using high-speed cameras, Eltz analyzed the courtship behavior of the males and demonstrated that the scents are released during hovering flight at the courtship area by a complicated leg movement and spread in the air flow of the wing flap. The effort that the males put into collecting scents is enormous, and the morphological adaptations are extreme. All of this indicates that particularly "scented" males benefit greatly, for example by attracting females who are ready to mate, explains Eltz. The fact that the male scent bouquets are species-specific makes their use as a sex attractant even more likely.
Since research in the 1960s, researchers have known that ornithologist bees collect flower scents and conserve the volatile essences in pouches on their hind legs. The phenomenon, widespread throughout Central and South America, has far-reaching ecological and evolutionary consequences. More than 700 species of orchids - that is about ten percent of the entire American orchid flora - have taken advantage of the behavior of the perfume collectors and are pollinated exclusively and highly specifically by them. In addition, the orchids produce species-specific scents that attract one or a few of the approximately 250 species of orchid bees. When the scents are collected, the pollen is then stuck to the male bee's head, leg or back by sophisticated mechanisms and can be released for pollination the next time you visit an orchid flower. Despite the wide spread and conspicuousness of the phenomenon, it was still unclear what the male bees do with the accumulated odors. © Heinrich Heine University Düsseldorf