Backyard Biology

Nature stories from my backyard and beyond

Nature Stories

The Solitary Bee and

the Lady Slipper

Friday, June 8, 2012

It is supposed to be an equal partnership, working to the benefit of both parties. That is the way they evolved, that is the way nature intended it. Bees pollinate the flowers and in return, the flowers supply the bees with a source of food in the form of nectar.

In order to reproduce, a pollen grain from one plant must unite with an egg from another plant (of the same species). This fertilized egg will develop into a seed which will grow into a plant. The dilemma is, since plants are stationary, how do the pollen and eggs meet? In some cases, plants rely on the wind. A plant will release its pollen into the air and the wind will carry it to other plants.
Other plants enlist the aid of insects such as bees. The plant attracts the bees by producing nectar on which the bees feed. Nectar is a sweet smelling concentrated sugar solution (if you would like to see what nectar tastes like, find a bunch of clover, remove an individual flower, put it in your mouth and sip it like a straw). While feeding on the nectar, the bee rubs against the pollen which sticks to the bee's body. While the bee also uses the pollen as food, some of the pollen may fall off the bee when it visits the next flower. In this way, the pollen from one flower makes its way to another flower where it may fertilize its egg.
For the last few hundred thousand years, insects and flowers have been perfecting this relationship. Today, they are dependent on each other. If insects were to disappear, half the plants on earth, including many that we rely on for food, would quickly become extinct through lack of pollination.

Any successful business adventure is liable to attract its cheats and con artists. Nature certainly has its share. One such story is that of the solitary bee and the lady slipper.

Unlike the honeybee and the bumblebee, the solitary bees are - solitary. They live alone. Each bee is a queen in her own right, but a queen without a court. Each bee must construct her own nest, provision it with food, lay an egg, close up the nest and then start again. Depending on the species of bee, the nest might be a hole in the ground, a hollowed out twig or even a tunnel bored into the side of a house. Typically, the nest is provisioned with both pollen and nectar, then an egg is laid and the hole is capped. When the egg hatches, the larva eats the provisions, grows to adulthood and leaves the nest, to start the process over again.

Lady SlipperThe pink lady slipper is one of our woods most lovely, delicate spring flowers. But there is more to this beauty than meets the eye.
The lady slipper is pollinated primarily by large solitary bees. The bee is attracted to the sweet smell of the flower. Excited by the prospect of a nectar meal, the bee forces its’ way into the bulbous flower. However, once inside, it discovers - no nectar! It has been tricked. Now it is time to leave. A light patch at the back end of the flower shows the bee the way out. Near the exit the bee must squeeze beneath the flowers’ anthers, where the pollen is produced. In exiting the flower, some of the flowers’ pollen sticks to the bee, not much to show for its efforts.
Now comes the amazing part. In order for this pollination scheme to work, the bee must be tricked into entering a lady slipper again! This time, its travels through the flower result in its brushing against the plants' sticky stigma. Pollen from the first plant sticks to the stigma, which contains the eggs. The pollen from the first lady slipper fertilizes the egg of the second lady slipper, and seeds are produced.
Experiments have shown that the bees quickly learn to avoid the lady slippers. Therefore the plants must rely on young bees just emerging from their nests. Later in the year, the bees are too experienced and avoid the lady slippers.
For this type of pollination to work, the bees must not be tested too often. Perhaps this is why lady slippers are never very abundant in any one area. With fewer plants, the bees will have visited them all before learning to avoid them.

Once the lady slipper has been pollinated, it is time for the seeds to be spread. If the seeds were to just fall to the ground, there would be large numbers of lady slippers in one spot, the bees would get wise and many plants would go unfertilized. To prevent this, the seeds of the lady slipper are tiny. They are so small that they will be carried for long distances by the wind. This insures that the plants will be spread far and wide. However, when they land, they are not able to begin growing, for the seeds are so small that they lack a supply of food. Most other types of seeds carry with them the food they need to grow until their leaves have emerged and they can produce their own food. Since the lady slipper seeds have no food, they need help at this early stage. This help comes in the form of a fungus living in the soil. The fungus invades the seeds' root system and begins to pass food to the lady slipper seed. Once the seed has sprouted leaves and begins to produce its own food, the fungus now extracts nutrients from the lady slipper. Unlike the lady slipper and the bee, this is a true partnership, benefiting both parties.

The lady slipper is an amazing flower. For it to survive, it must trick a bee into entering its' flower twice. Then it must disperse its seeds far and wide. Finally, the seeds must land in soil with the right kind of fungus. But the most amazing thing about the lady slipper is that this all happens with no conscious thought from the flower. It just happens!