In the list of dark yet extremely successful peculiarities of nature, there is something that truly shocks with its ingenuity.
It is well known that there are flies that specialize in feeding on the bodily secretions of dead or dying bees. The example is simple: a spider catches a bee in its web. The bee desperately tries to escape and the fly hovers over it to taste its delicious juices, stealing from the spider's meal.
But that's not what impresses so much. Or at least it's not the only thing.
There is a plant that specializes in deceiving these flies by emitting from its flowers the same scent that a dying bee emits or one that is struggling to survive. It traps the flies inside its flower for about 24 hours with absolutely nothing to eat – not even pollen or nectar. It only releases them once the flies have had enough time to go through all parts of the flower searching for food or an exit, and having taken with them a sticky 'package' of the plant's seeds (which, if you didn't know, is found within the pollen).
When they emerge from the flower, weakened and hungry, they may, like 'fools', fly to the next 'deceptive' flower only to be trapped again. In this process, they may leave this sticky package, fulfilling the dark and insidious purpose of the plants for pollination and creating new flowers that will trap them again in the future.
The grandeur of nature at its highest level.
The botanical species that impressively stars in the above story is called Ceropegia sandersonii, also known as 'parachute flower' due to the shape of its flowers that resemble a parachute.
This plant is a climbing species native to South Africa and is not alone in these types of deceptive practices. 4-6% of plants (about 15,000 species) achieve pollination through deceptive methods. One of the most famous examples is some Orchids whose flowers resemble a female bee, thus attracting male bees.
Natural mimicry is just one way that plant flowers deceive insects. They can also use chemical substances to trick their pollinators. The incredibly charming Orchid ‘Calypso bulbosa’ that lives in the rocky mountains above Denver and Boulder emits an enticing scent of fake pollen and nectar to attract bumblebees but without any real nectar or pollen as a reward. And this scent varies greatly from flower to flower, making it impossible for the insect to associate a specific scent with the deception, leading it back again and again to the same result.
The Ceropegia presents its own corresponding display, uniquely and intricately combining a blend of scents akin to that of a dying bee and a peculiar trap.
Scientists knew that plants of the genus Ceropegia use 'deceptive' methods to attract insects to their flowers, but they did not know exactly how they do it. They also knew that the diptera that usually pollinated the flowers of Ceropegia were kleptoparasitic, meaning they stole their food from other animals by feeding on the bodily fluid secretions of insects that were dying or had died.
Only the females of these diptera (often of the species Desmometopa) are kleptoparasitic (like in mosquitoes where only females suck blood), because they need the protein from these secretions to create eggs. Scientists had hypothesized that these kleptoparasitic diptera used volatile odors (also known as alarm pheromones) released by trapped bees, suggesting that Ceropegia may mimic the release of such odors.
Scientists hypothesized that if the flowers of Ceropegia mimic the 'food' of the dipterans Desmopetopa, then its flowers would emit an unusual mixture of scents that are not typically found in flowers, and these scents would coincide with those emitted by a dying bee.
Indeed, the most common visitors to its flowers are the kleptoparasitic diptera of Desmometopa. Inside experimental flowers, mainly female insects were found, reinforcing the theory that the flowers mimic a scent that the 'ladies' cannot resist. Moreover, 60% of the scents emitted by the flowers of Ceropegia resemble those emitted by the subspecies of European bees and those of Southern Africa when experimentally placed under threat conditions. Additionally, the odors emitted by the bees were highly variable, and the flowers of Ceropegia even copied this, significantly altering their own scents.
The combination of the compounds that release the flowers of Ceropegia is emitted by no other flower plant in the world and by no other insect except for this specific bee.