APRIL
1999

 

 

 

By
Tom Turpin
 
Professor of
Entomology
Purdue University

 

 

 

 

 

04-22-99

Flowers Market Themselves to Insects

April showers bring May flowers. Or so the old saying goes. May flowers are not the first flowers of the season. However, it is during the month of May that flowering plants go into full swing for the growing season.

We humans appreciate flowers. So we look forward to the time each year when the beautiful blossoms of the plant world adorn the landscape.

In our adoration of the beauty of flowers, we are tempted to believe that Mother Nature placed them there for us. But think again! The flowers are there for insects. We humans are merely spectators to a great marketing scheme in nature—marketing for the sake of pollination.

Pollination is the process whereby plants reproduce themselves. Pollination of plants results in the production of seeds. Seeds germinate and grow into plants. And plants produce more seeds. And so it goes in one of the endless cycles so common in nature.

Plant pollination sometimes depends on outside forces to move the pollen from place to place. The wind does the job for some plants. Other plants depend on insects to transport the pollen from flower to flower. 

Insects, like most things in nature, can be described as selfish. They don't work for nothing. Plants pay the insects to carry pollen by offering a little sip of nectar—a sweet bribe to labor for the plant's benefit.

It is not enough for plants just to provide nectar. In nature, as in the modern business world, sales and marketing are driving forces. So plants have evolved elaborate schemes—flowers—to entice insect pollen carriers.

The bright colors of flowers are billboards and neon signs for insects. To a flying insect, a meadow in flower must appear much like the Las Vegas strip to incoming airline passengers. Each flower radiates an enticing message: Stop here!

But there is more. Frequently, the flower emits a wonderful aroma. An aroma that further entices the insect visitor to stop for a sip. An aroma that to an insect is enticing as a hawker at a Las Vegas casino. But as Friedrich Barth says in his book, “Insects and Flowers,” “it is not enough to just get the insect to stop at the establishment, one must still find the door.”

So like any good business, the flower has signs to the entrance. These signs are known scientifically as nectar guides. Nectar guides are frequently associated with ultraviolet reflections on the flower. These are unseen by humans but are blinking neon signs to insects that see well in the ultraviolet portion of the light spectrum. The nectar guide is saying to the insect: follow this path to the sweets hidden deep in the flower. 

The path to the nectar results in the insect contacting pollen. Some of the pollen is trapped on the insect's body. For the flower, it has accomplished the first marketing goal. The insect is now a pollen carrier.

There is more to the story. For pollination to be completed, the insect must carry the pollen to another flower. For this reason, flowers just give out small doses of nectar. The insect, frequently a bee, must go to other flowers to get all the nectar it can hold. When this happens, the pollen from one flower is transported to another. To flowers, it is now mission accomplished! 

So the next time you stop to smell the roses, remember that you are benefiting from a close association between insects and flowers. It's an elaborate marketing scheme perfected by flowers involving advertising, supply control and repeat customers!

 

Writer: Tom Turpin
Editor: Olivia Maddox