Humans and animals go to any lengths to attract members of the opposite sex, including the use of aliases and lies. More than 10,000 species of beautiful orchids also utilize deception in order to be pollinated. We usually think of flowers as offering food to the insects that pollinate them. But on the contrary evolution has produced many flower species that pretend to have food that insects want, emitting scents of coconut or even rotting meat. Surprisingly some orchids, appear to offer the promise of sex, in fact they have evolved to resemble female versions of certain insects.

We humans always don't give plants nearly enough credit. We tend to call a fellow human as a potted plant or a helpless person a vegetable. But we fail to remember that although the plants lack the ability of locomotion they have worked to develop a bunch of tricks taking into account their key fact, which is rootedness. How can one spread genes when they are stuck in a place? Considering one of the largest diverse families of flowering plants the orchids, we see that there are over 25,000 species of orchids, that have colonized six continents on every imaginable terrestrial habitat, (from the deserts of western Australia to the cloud forests of Central America, from the forest canopy to the underground, from remote Mediterranean mountaintops to living rooms, offices, and restaurants the world over) for over 80 million years. The secret of their success is deception, though there are a few orchids that offer food for the insects and the birds that carry their pollen from plant to plant. But one third of the species, save on nectar and evolve a clever deceit either, visually, aromatically, tactfully or all three together. Some orchids attract the bees with the promise of food by mimicking the appearance of nectar producing flowers, while some others attract gnats by producing nasty scents similar to fungus or rotten meat, while some others promise shelter mimicking their appearance to burrows or brood rooms. But the most cleverful deceit of all is offered by a few orchids that hold the promise of sex (not exactly normal sex, but really weird sex).

One of the most ingenious and diabolical of orchids is the Ophrys, which uses the reproductive strategy of sexual deception and pseudo copulation. It offers no nectar or pollen, but the pseudo-copulation strategy of the orchid enables it to spread its genes widely. It seduces the male bees with the promise of bee sex by mimicking the appearance, scent and also tactile experience of a female bee, and ensures its pollination.  These orchids grow mostly like roadside weeds. They bloom in April. The lower lip or labellum of these flowers has resemblance to a female bee as viewed from behind. This pseudobee in some Ophrys species comes along with fake fur and looks as though the female bee has had her head buried in a green flower. To make the deception even stronger, the orchid emits a scent very close to that of the pheromones of the female bee.

Getting an orchid pollinated through sexual deception works like this: the real male bee settles down on the labellum that resembles the female bee, and attempts to mate. In the midst of these futile efforts the bee jostles the orchid’s column and two yellow sacks packed with pollen are stuck on to his back with a quick drying glue like substance. In frustration, the bee flies off with the pollinia still attached to his back in search of a real female companionship. Furthermore, duped males are not likely to return to another flower. They even ignore other plants of the same species. Therefore, only about 10% of an Ophrys population gets pollinated. This is enough to preserve the population, since each Ophrys orchid produces about 12,000 minute seeds.

Darwin was fascinated by orchid pollination strategies, and has taught us much in The Various Contrivances by Which Orchids are Fertilised by Insects. Darwin identified floral structures in orchids “as perfect as the most beautiful adaptations in the animal kingdom." He painstakingly demonstrated how even the most unlikely features of these flowers serve a reproductive function, and many of these structures are so perfectly adapted, both to the plant's requirements and the morphology of its pollinators. Darwin speculated the existence of a moth with a 12 inch long tongue that had never been observed, when he tried to explain why the star orchid of Madagascar would secrete a drop of nectar at the tail end of a foot-long floral spur. Justification of this fact appeared two decades after Darwin’s death, while entomologists found the tongue of a newly discovered hawk moth to be nearly a foot long.

Now the pollination strategies have raised many questions in the mind of evolutionists like,

1.       Why haven't all orchids stuck with the more straightforward pollination strategies based on nectar reward?

2.       How in the world did their sexual practices get so elaborate?

3.       What did the pollinators gain?

They have also come up with fascinating answers to many of these questions. Evolutionary biologist John Alcock gives two explanations why some orchids would have evolved to avoid the nectar award.

(i)                 Botanists experimented by adding nectar to normally nectarless orchids and found that pollinators hung around longer visiting other nearby plants in the same area. This does not suit orchids, since these breeding results in low quality seeds. But when mixing one’s genes with distant mates, the offspring had increased vigour and maximised fitness. The sexual frustration of a deluded bee is the orchid’s reproductive strategy. The bee travels some distance to make sure it does not make the same mistake again and if things work out for orchid, the bee ends up pseudocopulating and leaving his package of pollen. Also distant orchids are likely to look and smell differently from the first, which is again orchid’s strategy to prevent bees from learning not to fall for a flower. 

(ii)               Nectar is metabolically expensive, and other different animals can get attracted that may not deliver the pollen to the right target. So attracting a male of particular species of bee ensures that pollen will end up precisely where you want it.

It is fair to say that orchids have opted for quality rather than quantity. This sexual deception does not fool all the pollinators at all times and does fool some of them sometime, which is quite enough for an orchid, because the pollinium contains large number of pollen grains and when they are delivered, the resulting seedpod contains enormous number of seeds. Orchid seeds are so tiny that they do not contain the source of food needed for the developing embryo. So the orchid has to count on strangers like endophytic fungus. If everything goes right, the fungus infiltrates the orchid seed and provides nutrients for the embryo.

 Now when we consider the orchid Coryanthes, which is the Central American bucket orchid, it gives off a powerful perfume of apricots and eucalyptus. The flower drips a clear slightly viscous liquid (not nectar), directly above the labellum that forms a deep bucket.  Euglossine bees are attracted to this type of orchid. These bees scrap fragrances from the waxy surface of the flower using their front legs and transfer the scent to the tibia sacs carried on their rear legs. The bee also collects fragrances from other leaves and fungi ad then mixes the perfume with the hand and spreads it on his body. He then flaps his wings and releases the scent of camphor and flowers to summon a female. Now when the bees jostle each other for scents, one or more of them lose his foot on the petal and slips into the bucket. This makes the bees wings temporarily useless. The bee then struggles to climb the slippery walls of the bucket, making his way out of the pool through a marrow passage which leads to the back of the flower. The bee squeezes himself through the tunnel, and passes beneath a spring loaded device that dusts a pair of yellow pollinia onto his back. The bee then dries off his wings and flies to another Coryanthes, falls into the bucket again, and on his way through the tunnel, unknowingly leaves his yellow backpack on tiny hooks which are adapted for this purpose. Thus pollination is completed and the orchid closes, collapsing its petals into a piece of crumpled yellow tissue. In this case, the orchid and its pollinator are benefited.

Natural selection can be quite harsh sometimes. When considering the tongue orchid, Cryptostylis, it lures its pollinator by spreading a scent similar to the pheromone of the female wasp. The male wasp sits down on the tongue like labellum, tail first and starts copulating with the flower until the sticky pollinia attaches to the insect's posterior like a pair of yellow tails. More often the wasp actually ejaculates onto the flower which is bad news for both the wasp and the orchid that depends on him. But the reason for this maladaptive behaviour is explained as follows. In some insect species, females can reproduce with or without sperm from male. With sperm they produce both male and female offspring, but without sperm, they produce only male offspring. Thus, by inducing the wasps to waste their sperm on its flowers, the tongue orchids are decreasing the amount of sperm available to female wasps, thus resulting in larger population of male wasps, which means more pollinators.

Learning all this makes us wonder, if we too have fallen a prey to these deceptive charms. We humans use them to communicate our romantic intentions, and also extract essences for perfumes. Love for orchids among humans started around 1818 when an English plants man rescued a discarded bulb of orchid that was being used as packing material on a shipment of tropical plants. The flowering of that bulb kindled a Victorian passion for orchids. Human-hybridized orchid bloomed early in the Western world around 1856 and ever since then, humans have become important orchid pollinators too, but unlike the orchid bees, humans are tempted into assisting in its pursuit for world domination. Till date there are some 100,000 registered orchid hybrids. This was not in the orchid’s plan, but it only happened as a blind chance. But the moment the orchid hit the desires of humans, it conquered a whole new world and created a big list of animals, more than happy to do its commands. We are all orchid dupes now.