CHAPTER 1
UNDERSTANDING POLLINATORS
Bees need flowers for the nectar and pollen they provide in return for pollination services.
WHAT IS POLLINATION?
Imagine a summer without blueberry pie, without icy, cold watermelon. Not into sweets that much, you say? Picture your tortilla chips minus the salsa and guacamole. If that doesn’t worry you, this one will: how would you get along without that mid-afternoon chocolate bar or your morning coffee?
Without pollinators, these delicious treats would disappear. Oh, you’d still have corn and wheat, although that might get a bit dull. Pollinators are responsible for every third bite of food you take, but more importantly the colorful and healthy fruits and vegetables that perk up your dinner plate. But it goes deeper than that. Two-thirds of the entire world’s plant species depend upon animal pollination. Plants that feed insects that feed birds and frogs that feed the snakes and owls and on up the food chain…you get the idea. Without the vital services of pollinators, the whole grand scheme falls apart.
Much of this tasty lunch was made possible by pollinators.
It could be said that insects run the world. Yet many people still don’t realize the critical role pollination plays in maintaining human sustenance and a healthy, diverse ecosystem. Some possess a vague memory from biology class, a diagram of flower parts and something about bees. Mention pollen and their first thoughts go to the invisible irritants that float in the air, stuffing up their noses and making their eyes itch and water. Pollen is that pesky yellow dust on their cars when they park outside. Pollen is the orange stain on their shirt when they brush up against lilies in a hotel lobby bouquet.
Far from a nuisance, pollen is the magic dust that makes everything possible. Gardeners marvel at tiny seeds and how they produce such a beautiful variety of plants. Pollen is fascinating, too. It comes in many shades besides yellow—pale gray, light green, brick red, steely blue, black, and many gradations in between. Beekeepers can often learn where their bees forage by noting the pollen color they bring back. You’d be surprised at some—white snowdrops, for example, have red pollen, and red poppies have black.
Pollination is the transfer of these pollen grains from the anther of one flower to the stigma of the same or another flower. This helps the plant to successfully reproduce. Some plants are wind-pollinated; a few are even pollinated by water, but most depend on insects, birds, and a few other animals.
Bees collect different shades of pollen depending upon the flower source.
Plants that use the wind to reproduce throw out huge quantities of lightweight pollen grains (the ones most responsible for all of those miserable symptoms) that fly through the breeze. Many trees, such as willow, birch, walnut, conifers, and even grasses rely on this system, one that takes advantage of an abundant natural resource without expending energy on producing conspicuous flowers to entice insects. Their flowers don’t produce nectar and have little to no fragrance. Their stamens, like those on birch catkins, are exposed to make it easier to catch pollen passing by. With this scattered shotgun approach, though, enormous amounts of pollen miss their mark and are wasted in the process.
Pollen sticks to this long-horned bee’s hairy body. It’s then transferred as the bee moves from flower to flower.
Insect pollination, on the other hand, is highly efficient and accurate. Pollen grains are held on the anthers at the center of the flower. When bees, butterflies, and other pollinators visit the flowers looking for nectar, they brush against the flower’s anthers, catching the pollen grains on their bodies. Bees also seek their share of the pollen, packing it into specialized structures on their hairy bodies to transport back to their hive. As pollinators move from flower to flower, some of the pollen falls off and sticks to the stigma, the prominent female flower part that serves as the entrance to the flower’s ovaries. The pollen grain is made up of two cells: one forms a pollen tube which then directs the other generative cell taking the pollen down into the depths of the flower where it fertilizes the waiting egg. Once fertilized, this enables the plant to make seeds.
Within this process there are different types of pollination. In self-pollination, pollen moves within one flower or between flowers of the same plant. These plants are described as self-fertile. Cross-pollination occurs when pollen moves from one plant of the same species to another. Self-fertile plants may indeed produce flowers and fruit but lack the genetic diversity that comes from repeated cross-pollination. This genetic diversity helps plants adapt to changing conditions, pests and disease, and other stresses, a quality that becomes more and more important with climate change.
THE POLLINATORS
HONEYBEES
Lemon chess pie with blackberry compote, courtesy of cross-pollination.
Honeybees are native to just about everywhere other than North America—Europe, Africa, the Middle East, and Central Asia. The European colonists introduced them to the New World in the early 17th century, and since then they have made themselves at home and become a vital part of our agriculture—both for honey production and crop pollination. They vary from gold to brown to black. Most importantly, though, they all are fuzzy, which is ideal for collecting loads of pollen that they store in their pollen basket, a specialized body part called a corbicula, as they buzz back to the hive.
As social insects, honeybees live in a colony organized in castes that determine each bee’s job in the hive. The queen is the largest bee in the colony and solely responsible for laying eggs. The males or drones are there for mating purposes only. In this female-driven society, the worker bees industriously perform a number of duties in a hierarchy based on age. The youngest clean the hive, nurse the brood, and attend to the queen. The next oldest workers help to guard the hive entrance. The very oldest workers forage for nectar and pollen.
A beekeeper inspects his bees and the honey frame from their hive.
Honeybees are generalist foragers, meaning they visit a variety of flowers. The location and quality of flowers they find is communicated to other workers through pheromones and an intricate “waggle dance.” They are not adapted to every plant they encounter because they are a foreign species, though, and sometimes practice nectar robbing. This involves tearing a slit in the side of a flower to extract the nectar without having to enter the bloom or pollinate the flower.
NATIVE BEES
Bumblebees (49 species in US): Most cartoon bees are based off the likeness of bumblebees, making them the most beloved and recognizable of all bee species. Yet they only account for 1.4 percent of all bee species in the US. Fuzzy and chubby, they are usually black and yellow, although some can have orange, brown, or even white bands. They are generalists and forage on a wide variety of flowers. Bumblebees are able to shake pollen from a number of flowers that honeybees can’t access. Using “buzz pollination,” they grab the flower and vibrate their wings at a high frequency until the pollen falls from the blossom. They are important pollinators of tomatoes, watermelons, and blueberries, among other food crops.
A bumblebee uses sonification, or “buzz pollination,” to release pollen from a tomato blossom.
Carpenter Bees (36 species in US): These bees come in a range of sizes. The bigger bees, such as the common Eastern Carpenter Bee, are often confused with bumblebees; however, their shiny black abdomens distinguish their species. Their big green eyes are notable, too. People are not always happy with carpenter bees’ habit of chewing into soft wood for nesting purposes.
They are generalists in their foraging, valuable pollinators in the vegetable and flower garden, up and out at work early in the mornings. Like bumblebees, they can use buzz pollination. They are known to practice nectar robbing (see page 15) when they can’t fit their large bodies into some blooms.
Cuckoo Bees (499 different species in US): The jury is still out on whether these bees provide much, if any, pollination service to the flowers they visit. As parasites that lay their eggs in other bees’ nests, they have no need to gather pollen. Researchers are studying whether some pollen manages to adhere to their nearly hairless bodies (possibly through static attraction), therefore contributing to pollination.
Digger Bees (332 species in US): Most information about digger bees addresses how to kill them rather than how to conserve them. People find their bee-dug burrows distressing, yet they are valuable garden pollinators.
Sweat Bees (287 species in US): People are familiar with these bees for an unfortunate reason. As the name implies, these bees are attracted to human swe...