Orchids display such a crazy diversity of structure, color, pattern, and fragrance. This is Part 3 in my series of blog posts investigating orchid pollination strategies. What makes orchids so weird?
It just makes scents
Many insects produce volatile pheromone cocktails to attract mates, but there is a group of bees that actually collects compounds from its environment. Euglossine bees are beautifully shiny neotropical bees. The males spend their time searching for fragrant chemicals to collect and store in their enlarged hind limbs. Presumably the scents are then used by the male to attract mates, but female attraction to fragrant male euglossine bees has yet to be demonstrated.
The male bees are so focused on collecting scented compounds that they can easily be attracted by setting out any kind of smelly oil in the jungle. An orchid that could exploit such a drive would be able to attract an abundance of pollinators. That is precisely what Stanhopea and Catasetum orchids have done. The flowers provide a surface covered in smelly volatiles inside a strangely contorted set of petals. The petal arrangement is such that any euglossine bee that flew in to collect his perfumes would rub up against the pollen and take it with him when he leaves.
Other interesting facts about euglossine bees:
There is a species that is attracted to and even collects large amounts of DDT (dichlorodiphenyltrichloroethane) insecticide with no apparent problems.
Also, if you are a fan of The Big Bang Theory, you may have heard that a new species of bee was named Euglossa bazinga. True fact.
Stanhopea tigrina flowers from the bottom of the plant so that the flowers hang upside down. The lower lip of the flower is covered in fragrant compounds that attract the male euglossine bees.
This is Part 2 in my series highlighting the awesome diversity of orchid pollination strategies. See Part 1 to learn about sexual deception in orchid species. Today we will investigate another strategy that orchids have evolved to attract insect pollinators:
Home Sweet Home
Lady slipper orchids, members of the genera Paphiopedilum and Cypripedium, are called slipper orchids because they have a cupped lower lip, or labellum. The flower often has coarse hairs, spots, and stripes, giving them an elegant and alien appearance. These features function to attract female bees.
Some species of bees lay their eggs among aphids to provide food for their newly hatched larvae, so they are looking for leaves covered in dark hairy spots. Other bees look for a dark hole or den to deposit their eggs. Seeking a good place to leave her young, the bee lands on the orchid, gets trapped inside the labellum, and carries pollen with her when she escapes.
This Cypripedium macranthos has a dark labellum, tricking the female Bombus bee into thinking she has found a good den in which to lay her eggs.
The short answer: pollination. Orchids have evolved a huge variety of pollination strategies. While most flowering plants use bright colors, fragrant scents, or nectar rewards to attract pollinators, many orchids exploit the pollinator’s need for mates or nesting sites instead. The result is an awesome diversity of flower shapes, colors, patterns, and chemical cues. In a jungle filled with fragrant showy flowers, how do you stand out from the crowd?
This week I will highlight just a few of the super cool pollination strategies used by orchids, illustrated by yours truly.
1. Sex Appeal
Many orchids are sexually deceptive, meaning the flowers mimic female wasps. These flowers are shiny, furry, patterned, and some even have eyespots. Almost all known species of sexually deceptive orchid come from Europe and Australia.
In addition to mimicking the looks of a female wasp, these orchids also produce the chemical compounds that mimic the pheromones used by wasps. Female insects produce chemical signals comprised of blends of volatile compounds. The chemical identity and relative concentration of chemicals act as species-specific signatures. Amazingly, sexually deceptive orchids have evolved to produce compound blends with remarkable similarity to the wasp’s pheromones.
The Mediterranean orchid species, Ophrys mammosa, uses both visual and chemical cues to attract the male wasp, Andrena fuscosa. The female’s velvety body with reflective blue pattern and shiny blue eyes are part of the orchid’s flower.