America’s Bee Crisis: Part 3 – Native Bees Get It Done!
Generalist Species: ones which thrive in a broad range of habitats or on a wide variety of foods.
Specialist Species: those which can survive in only a limited geographic area, or on a narrow range of foods.
That seems pretty clear. Humans are generalists whose range encompasses pretty much all of Earth and we eat just about everything. Pandas are specialists who survive solely on the bamboo that grows in the forests of China. Our adaptability has led to our success, while the panda’s immutability may lead to its demise. But consider this: If much of the food we grow is pollinated by a single species of insect, are we truly generalists? In a way, we have specialized our system of food production by relying so heavily on the European honeybee. Thus, we have exposed ourselves to the risks that other specialist species face – we have made our diet precarious. But we can still generalize crop pollination by including our native bees, and the benefits of doing so will reach far beyond making our food supply more secure. In fact, native bees can help us produce more abundant and nutritious crops. How? Because they interact with flowers differently from honeybees.
America’s Bee Crisis: Part 3 – Native Bees Get It Done!
Nature’s Grand Puzzle
Everywhere on Earth we find evidence of coevolution, or species that have evolved together and interact in a unique way. They are more successful together than they would be apart, and sometimes depend on each other for their survival. Bees and flowers are two such species, yet this simple explanation belies their complex relationship. For just as there is a kaleidoscope of flowers on the Earth, so there is of bees.
All bees share the same basic anatomy, but they differ in ways that are important to pollination: size, furriness, type of pollen-collecting hairs, and tongue length. A very small flower will need a tiny bee to explore it’s recesses. Temperate plants need bees that are adapted to cold weather. A wide, flat flower, like a daisy, offers its nectar freely to any visitor, but a deep, bell-shaped flower needs a bee with a long tongue. In this way bees and flowers are like puzzle pieces; some fit together and others don’t. When a flower and a bee aren’t a good fit, incomplete pollination is the result.
For many years our ignorance (or perhaps our arrogance) led us to believe that any bee could pollinate any flower, and that honeybees, being so easy to domesticate, were the best choice for crop pollination. But though it may be possible to force two puzzle pieces together without them being a perfect fit, you will never be able to complete the puzzle. In this way, we have been trying to use honeybees as a sort of universal puzzle piece, and it’s not working as well as we’d hoped. There truly isn’t one bee that suits all the flowers of the world, and this includes the flowers that become our food.
Honeybees are industrious insects, and extremely efficient at the work that they do. Of the many thousands of workers in a hive, each and every one has a unique job to do; some tend the Queen; others care for the larvae; a few will be sentinels, guarding the hive; but many more are foragers. Foragers bring back nectar to make honey, and pollen to feed their young. Foragers can be very specialized in their jobs, so that one bee may collect only pollen, while another collects only nectar. A bee gathering only pollen or only nectar will not visit all parts of the flower to achieve pollination.
Honeybees have a tongue of moderate length – it is neither short nor long. This allows them to visit a wide variety of flowers, but it also prevents them from nectaring from deep flowers. However, bees are clever! They have learned to chew a hole at the base of a flower to access the nectar, bypassing the flower’s reproductive parts. This is called “nectar-robbing” because the bee gets the nectar without pollinating the flower.
Like all bees, honeybees have six legs. On their hindmost legs are corbiculae, or pollen baskets, for carrying pollen. Honeybees are very good at tightly packing their baskets with moistened pollen so that little falls out in flight or while stopping at flowers. It’s fun to plant a variety of flowers in the garden and watch the honeybees fill up their baskets with different colored pollen! However, since the pollen is so well-secured in their baskets they mainly aid in pollination by the hairs on their bodies, which small amounts of pollen cling to and fall off of eventually.
Everyone’s favorite bee! Our fuzzy friends the bumblebees are so much fun to watch buzzing around the garden. But all that fuzz serves a useful purpose: it insulates the bumblebee, enabling her to fly and visit flowers in damp weather. Because she wears a fur coat and hibernates underground, the bumblebee is well suited to areas with severe winters. Bumblebees can also raise their body temperature by vibrating their wings, allowing them to fly when morning temperatures are cold. A bumblebee’s fur also serves the happy function of becoming electrostatically charged while she is flying; when the bee then lands on a flower her charged fur is like a magnet picking up pollen and carrying it to the next flower. With all that fur she’s just kind of a messy bee. She’s got pollen all over and it brushes off everywhere she lands.
There are more than 50 species of bumblebees in the U.S., and they have tongues of varying lengths, but overall the bumblebee is a long-tongued species. They excel at pollinating flowers which are deep and narrow. Additionally, bumblebees show a predilection for these complex flowers.
Bumblebees are also masters of buzz-pollination. This is a really neat trick! You see, some flowers don’t give up their pollen so easily, and may even have an opening that many bees can’t fit in. No problem for the bumblebee! She can grab onto a flower and vibrate her body to shake that pollen out. It sticks to her fur and she gathers it up to pack in her pollen baskets. While she is shaking the pollen out, she is also distributing it within the flower, achieving pollination. Some plants that benefit from buzz-pollination are tomatoes and blueberries. There are other native bees who can buzz-pollinate as well, but the honeybee cannot. (Watch a cool video of buzz-pollination here!)
While honeybees and bumblebees carry their pollen in baskets, most other bees carry pollen in scopae. Scopae are special coarse hairs that bees can pack pollen into. Each hair is like a branch, and together they form kind of a brushy mass for cramming pollen in. This is a messy job. A messy, messy job. It’s not nearly as neat or efficient as carrying pollen in a basket. These bees are dropping pollen everywhere they go. And that’s a good thing! Bees who carry their pollen in scopae are some of the best pollinators we have because their pollen is falling out all over the place.
Some solitary bees have scopae along their hind legs for carrying pollen. Bees of the megachilid family have scopae on the underside of their abdomens. Just imagine a fat bee belly covered in a thick layer of pollen clinging to some scruffy fur. An orchardist’s dream!
Another important point of distinction for the solitary bee is that by working alone to feed her young she interacts with a flower more completely than a honeybee. The solitary bee will always gather both pollen and nectar on her flights, as she needs both to provide a food cache for her offspring. This contrasts with the honeybee, whose job is specialized, and may collect only pollen or only nectar on a foraging trip. The solitary bee, by gathering both, is very thorough on her visit to each flower, spending time at both the top and the bottom, and achieving a high rate of pollination.
Variety is the Spice of Life
This is just a small sample of the thousands of kinds of bees in America. Some are active in the early spring, others in the late summer. Many are generalists, visiting all kinds of flowers; some are specialists, utilizing one particular flower only. Native bees have been largely overlooked in agricultural science for years, so we still have much to learn about their role in crop pollination. However, recent research suggests that we are marginalizing them at our own peril, for the reasons illustrated above and more:
- “Flower constancy” is the term used to describe a bee’s tendency to fly from flower to flower of the same species. This is crucial to pollination because flowers can only be pollinated with pollen of the same species. You can’t pollinate an apple tree with a plum, for example. Researchers have found that bees are less constant when they don’t face pressure from competing bees, thus lowering pollination rates.
- Competition for resources from increasing honeybee populations is having a negative impact on native bee populations.
- Well pollinated flowers – or those that are visited by a variety of bees – produce better quality fruit that has a longer shelf life.
Clearly we are indebted to native bees more than we realize. It is in our best interest to preserve and protect them, and yet through our actions they are struggling. Loss of habitat, lack of food, and exposure to pesticides are taking a heavy toll on our native bee populations. Their needs are not being met by our current industrial agribusiness model. Moreover, our focus on proliferating honeybee populations does not create solutions that benefit native bees.
These bees are beautiful. They are a joy to watch in the garden. They are hard working, conscientious mothers, and gentle pacifists. I don’t want to lose them. I hope you don’t want to lose them either. The good news is we don’t have to. We can still walk ourselves back from this precipice we’ve found ourselves on. We can give these bees space to live and food to eat, while also feeding ourselves. We just have to care. And then we have to act.
I hope I’ve given you enough information to make you care.
Learn how to act in Part 4. 🙂
P.S. This is a series of blog posts that will include a giveaway of 2 complete mason bee kits; be sure to follow me here and on Facebook so you won’t miss an installment!
The Nitty Gritty
Since acquiring my mason bees in 2008 I have developed a passionate interest in bees in general, and solitary bees in particular. This series is a culmination of my last 6 years spent reading books, scientific studies, and news articles, as well as observing bees in the wild. For further reading on this topic, I suggest:
For information about bee anatomy and bee species: Bees, Wasps, and Ants by Eric Grissell and Bees of the World by Christopher O’Toole and Anthony Raw (out of print).
For information about bee behavior and pollination habits: Attracting Native Pollinators and Pollinator Conservation Handbook (out of print) by The Xerces Society.
For information about bumblebees: Bumble Bees of the Eastern United States and Bumble Bees of the Western United States by Pollinator Partnership (both available as free online PDFs).