The sexual deception of orchids Anne Gaskett
The world’s largest orchid
grows several meters tall.
The tiniest is practically invisible.
Some bloom high up in trees,
while others live underground.
All in, there are around 28,000 species
of orchid on earth –
about as many as all the bird,
mammal and reptile species combined.
They grow all over the world,
bearing every imaginable colour, shape,
and pattern.
And there’s a cunning purpose
behind these elaborate displays:
many orchids trick insects,
sometimes even into having sex with them.
Like other flowers,
most orchids need to attract insects
to gather their pollen and
carry it between plants.
But unlike most flowers,
which attract a range of pollinators
with sweet nectar,
these masters of deception
deploy other tactics–
like pretending to be an insect’s mate,
letting off alluring scents,
and mimicking the appearance
of other species.
One of their most intriguing methods
is sexual deception.
Through a combination of sexy shapes
and pheromones,
orchids convince insects
to mate with them.
Take the bee orchid,
whose petals look almost exactly like
the velvety body of a bee.
This disguise is so convincing
that male bees land on the orchid
and try to have sex with it,
picking up pollen as they go.
Other orchids have evolved contrasting
colours and ultraviolet spots–
invisible to humans but
irresistible to insects.
Still others have tactile ‘love-handles’
that ensure insects are positioned
precisely for pollination.
When a male wasp lands on the
hammer orchid, for example,
his enthusiastic mating motion
flips a hinge in the flower,
forcing his body into the pollen.
At the next flower he visits,
that same hinge pushes his pollen-covered
body onto the stigma,
fertilizing it.
Some orchids make such convincing mates
that insects even ejaculate on them,
wasting valuable sperm.
But the most vital component of
sexual deception is scent:
orchids mimic the precise scent
of a single insect species.
This is possible because many insects
and flowers
produce simple organic compounds
called hydrocarbons,
which form a layer that protects
their bodies from drying out.
The precise blend of compounds
in this layer is species-specific.
Its scent can double as a way for insects
to attract potential mates,
known as a sex pheromone.
Over the course of many
thousands of years,
random compound combinations
have given some orchid species
precisely the same signature scent
as particular insect species.
This matching scent allows them to
attract male pollinators
who fall over and over again
for the flowers masquerading as females
of their own species.
Sexual deception isn’t the only trick
orchids have up their sleeves.
Their oldest scam is mimicking the shapes
and colours
of other nectar-producing flowers—
but without the sweet nectar.
Some orchids also masquerade as places
where insects lay their eggs.
One species not only has the colour and
appearance of rotting meat;
it emits a scent of decay as well–
drawing in flies who deposit
their eggs on the flower
and unwittingly pollinate the plant.
Other orchids look and smell just like
the fungi on which certain insects
lay their eggs.
Where do all these bizarre adaptations
come from?
Random genetic mutations in orchids
may result in a trait–
like a scent or a shape–
that, by chance, matches the needs
of a single insect species.
The huge diversity within the insect
world also increases the likelihood
that an orchid will find
a unique audience.
Able to make more seeds and offspring with
the help of its dedicated pollinators,
the orchid successfully reproduces
in isolation,
and becomes a new species.
But because of their dependence on
sometimes just one pollinator species,
orchids are also vulnerable,
and many quickly go extinct.
Over time, though,
more orchid species have formed
than died out,
and orchids are some of the most diverse
flowering plants.
They have such exuberant and otherworldly
shapes
that they occasionally deceive
human senses, too:
In their petals we see what appear
to be tiny, dancing people,
monkey’s faces, spiders,
and even birds in flight.