A fragrant perfume has brought many a man and many a woman together. Orchid bees, too, appear to rely on scent when it comes to choosing a partner. In the course of their lives, the males compile a species-specific bouquet that they store in the pockets on their hind legs. One day, they release it. In order to attract the female, assumes Tamara Pokorny, biologist at the Ruhr-Universitδt Bochum (RUB). She studies the flying perfume aficionados' collecting behaviour.
Compiling the ideal scent takes a bee's entire lifetime
A male bee's complete perfume is made up of 20 to 40 characteristic components on average. Generally, the bouquet of young individuals deviates strongly from the ideal blend, because they had not yet had the chance to collect as many scents as older bees. This is evident in the data gathered by Tamara Pokorny and Marko Hannibal when they worked as visiting researchers in Mexico. The scientist from the Department of Animal Ecology, Evolution and Biodiversity also found out that bees are aware of what they had already collected. Even if an attractive scent is available in abundance, the bees stop picking it up.
Each orchid bee species prefers a different type of tree
When releasing their bouquet, orchid bees select a tree trunk as the centre of their territory. The choice is not made randomly, as Tamara Pokorny knows. Together with a student team, she analysed the favourite trees of several orchid bee species in Costa Rica. The smaller species preferred branches or trunks with a smaller diameter, larger species those with a larger diameter. Generally, a smooth surface was more attractive than rough bark. Wind direction appears to be one of the factors that determine where exactly the male perches to distribute his scent.
Getting energy for exhausting flights
The Bochum biologist also studies the orchid bees' flight performance. The small insects do actually fly over distances of 50 kilometres. Tamara Pokorny has a theory regarding how they get the energy necessary for those long distances, without being forced to stop and feed from flowers. By moving their proboscises in a certain manner, the bees appear to concentrate the sugar solution that they are drinking. They excrete superfluous water, retaining only the energy source within their body.
Orchids, eucalyptus and feces
Orchid bees live in Central and South America and live up to three months on average. Members of different species are interested in different scents. Orchid flowers are among the most popular sources, but eucalyptus-scented eucalyptol also frequently contributes to the blend. However, it's not just substances that have a pleasant smell to humans that find their way into the pockets; some species consider skatole, a compound occurring in faeces, part of the bouquet.
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