IF YOUR partner drives you crazy by giving you the same old boring gifts every Christmas, spare a thought for the female orchid bee. Males only ever give them one thing – perfume. And although they go to a lot of trouble to make it themselves, some then go and add faeces to it. No wonder the females aren’t especially enamoured.
As bees go, the 200 or so species of orchid bee are a curious bunch: they are solitary and do not make honey. Instead, these brightly coloured insects spend their lives buzzing round the tropical forests of central and South America, searching for exotic orchids, which are the main source of the perfumes they blend.
Over his three to five-month lifespan, a male orchid bee will expend a huge amount of time and effort scouting for fragrances. When he finds a desirable scent, he smears a fatty substance onto the surface to extract the volatile oils – just like the enfleurage method once used by perfumers. Then he deposits the resulting mix in on his hind legs.
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Over time the fragrances combine into what Thomas Eltz, an ecologist at the University of Düsseldorf in Germany, calls a “rich and sexy bouquet”. Aside from humans, orchid bees are the only animals known to blend fragrances into perfumes. The big question is, why do they do it? While their habit of scent collection was discovered in the 1960s, it is only recently that biologists like Eltz have started to sniff out the reasons.
The importance of the perfumes is revealed by the extraordinary lengths the bees go to in collecting fragrances. Some species of bee visit more than 40 different types of orchid. “Orchids are rare,” says Eltz. “They’re at very low density and very scattered in the forests, so the bees must travel long distances. They spend a substantial portion of their energy and time on fragrance collection. This is their main job.”
The orchids have evolved to exploit the bees’ needs, luring them in with ever more exotic perfumes. In return the orchids get pollinated: over 700 species depend entirely on the orchid bee for this service.
The bees are not entirely faithful to orchids, however. They also gather scents from other flowers, fruits, tree sap and resin. And, like expert perfumers, they will seek out more challenging fragrances – a hint of rotting wood, a dash of faeces – to add complexity and depth to their perfumes. “Faeces gives the bouquet a… er, prominent note,” says Eltz. “Sometimes they smell lemony, of menthol or eucalyptus, sometimes flowery. Sometimes they just smell shitty.”
The most likely explanation for all of this hard work, says Eltz, is sex. For bees of all types, odours are a crucial means of communication, especially during courtship. While honeybees and bumblebees produce their own pheromones, orchid bees do not. And the perfumes blended by male orchid bees seem to contain a set of key odours unique to each species, suggesting that the males use the collected fragrances to make their own “pheromones”.
However, the perfumes are probably far more than a simple “here I am” signal. They might also be an advertisement of fitness. After all, collecting a wide range of fragrances requires stamina, strength and ingenuity. The richer and more complex your bouquet, the more likely you are to possess good genes. Or so biologists suspect. Finding out for sure is proving remarkably difficult.
Aside from collecting fragrances, a male orchid bee’s favourite pastime is hanging out at his display site, on stems and branches in the forest understorey, performing stunts such as wing buzzes or hovers. These are clearly courtship displays, and so are the focus of efforts to understand what the perfume is for. The problem is that matings are rare.
“You can stand at the display sites for weeks and weeks and not see a single one,” says Eltz. Until 2003, only six matings had ever been recorded in nature. The last of those, seen on Barro Colorado Island in the Panama Canal in 1991 by David Stern of Princeton University, took five months of observation.
Perfume wars
In 2003, Eltz and David Roubik of the Smithsonian Tropical Research Institute in Balboa, Panama, decided it was time to get to the bottom of orchid bee sex. They caught eight males of the species Euglossa hemichlora near Panama City and put them into a large container with 30 virgin females. Over the course of 11 days, they observed six copulations. All encounters were initiated by females approaching a displaying male and landing on his perch ().
High-speed video revealed that during their courtship displays, males perform intricate leg movements that transfer the contents of their leg pouches onto a comb-like structure on the base of their wings. Wing beats then waft the scent about.
Things got even better. Roubik later spent 40 hours watching display sites in Panama. His reward was to see two natural copulations. Both times, he says, the female approached the male “directly and rapidly” from downwind, suggesting she was drawn by his perfume (). This does suggest that male bees create their perfumes primarily to advertise themselves to females, says Eltz. “There’s no direct proof yet, but there’s lots of circumstantial evidence.”
The case is not closed, however. Bee perfume doesn’t only attract females: the most frequent visitors to display sites are other males, who also tend to arrive from downwind. The purpose of these visits is not clear, Eltz says. Maybe they are checking out the competition, or lurking near a rival with superior perfume in the hope of tricking an incoming female into having sex.
Roubik goes further. While he believes that females are attracted by the perfume, he doesn’t think this is its prime purpose. He’s pretty sure that male orchid bees use their perfume to intimidate their rivals.
Waiting at a display site for sex may be tedious, but if you’re interested in fighting it’s much more fun. When one male visits another’s display site, the encounter often leads to a lengthy bout of ritualised “jousting” in which the males fly at each other repeatedly, or face off before both suddenly zoom upwards. The bouts go on until one of the bees buzzes off.
According to Roubik, such jousting is all about claiming prime display territory: a winning bee will use a site until he dies or loses it in a joust. Despite the fancy flying, Roubik suspects the ultimate arbiter of victory is smell. During jousts the bees often smear perfume on their wings, he says. They also grapple antennae-to-antennae, as if testing who has the richest bouquet. “It’s a great emblem of your achievements,” says Roubik.
Despite their progress, Roubik and Eltz admit that we are only just beginning to unravel the mystery of the perfume-making bees. Of the hundreds of species out there, only 15 or so have been studied in any detail, and the composition of their perfumes varies greatly. Who knows what exotic and sexy fragrances remain to be discovered in the depths of the South American jungle – and what total stinkers, too.
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