(Updated, 11/25/16: fixed broken links)
Bees are amazing creatures, with their complex societies and unparalleled ability to pollinate plants*, so I like to learn about them when I can. One such opportunity recently was at a panel discussion about bees at Sonoma State University’s Insectpalooza. Sitting on the panel were three experts on European and California native bees: Dr. Eric Mussen an extension apiculturist from UC Davis, Dr. Gretchen LeBuhn from San Francisco State University (professor of entomology, founder and director the Great Sunflower Project, a citizen-science project focused on native bees), and Marissa Ponder, a researcher in Professor Gordon Frankie’s lab at UC Berkeley.
The bulk of the presentations were not about the European honey bee (Apis melifera), which is probably what most of us picture when we hear the word “bee” (I know that I do), but instead were on California’s native bees, which are found in about 1,500 different species. Beyond their role as pollinators, most native bees differ in many ways from honey bees, most notably that they live solitary lives and do not make honey**.
Current Thinking on Collapsing Colonies
Mussen talked mostly about European honey bees and the history and current status of colony collapse disorder (CCD). He noted that the current CCD is not the first time we’ve seen this – there was one that lasted about a year in the late 1800s, and one that lasted for 3 years in the mid-1960s. So, he asked, why has this one has been going on for 7 years? Mussen theorized that today’s beekeepers are better at nursing sick bees, thus the weak hives stick around longer instead of quickly dying off.
Among the interesting figures he presented included:
- An average honeybee has a foraging range of 4 miles, which gives a colony a 50 square mile area to collect food – or to get into trouble with poisons and pests.
- California has 780,000 acres of almond trees that require 1.5 million colonies of honeybees for pollination. But California has only about 0.5 million colonies, so 1 million are trucked in for the season (a 2006 article in the Agricultural and Resource Economics Update claimed that 60% of the nation’s bee colonies are used to pollinate almonds in California during blossom season).
Bees are the “Professional” Pollinators
Dr. LeBuhn focused on the native bees, enhancing her presentation with beautiful illustrations by local illustrator Noel Pugh (examples of his work are at the Great Sunflower Project and are in the Field Guide to the Common Bees of California). She started with some numbers: there are about 30,000 bee species in the world, 4,000 in the U.S. and 1,500 in California.
Then she got into morphology and behavior, noting that other creatures besides bees pollinate plants – beetles, moths, hummingbirds are a few – but they are “amateurs”, while bees are “professionals.” Bees have characteristics that improve their efficiency: special hairs to collect pollen, an electrostatic charge on their body that attracts pollen, and specialized mouth parts to reach into flowers. Additionally, some plants need buzzing at a certain frequency to release the pollen, and bees can generate many frequencies. As an example, LeBuhn mentioned that tomatoes release their pollen when excited by tone of 261 Hz (middle C), so one can place an excited middle C tuning fork near a tomato blossom to cause a pollen drop.
While European honey bees are generalists, visiting any flowers they can find, many California natives are specialists, preferring one species of plants for pollen, but visiting others to get nectar. Another important difference between European honey bees and natives is that most native bees are solitary, building nests in tunnels underground, or in a hole in a tree, or inside of a stem. Inside the nest you would find several chambers, each with one or more balls of pollen inside and an egg placed on top of one of the balls of pollen. Carpenter bees, for example, make walls that are like particle board to separate the chambers.
Native bees spend most of their life underground as an egg or larva, perhaps 46-48 weeks underground and 2-6 weeks above ground.
Native Bees Live in the City
Marissa Ponder, a researcher in the Professor Gordon Frankie lab at UC Berkeley, talked about native bees in urban and suburban environments, and enhanced her presentation with stunning photos by Rollin Coville. One of Frankie’s projects has been a test garden on the UC Berkeley Oxford tract at the edge of downtown Berkeley to get a sense of native bee diversity in a highly urbanized environment. In a small garden, surrounded by concrete and buildings, his team counted 85 species of native bees. This result – which I find to be amazing – is not so unusual, as Ponder’s other examples illustrated, like a front yard in another city (the name of which was illegible in my notes), in which researchers counted 68 species.
But despite these examples of diversity, people with gardens and yards can give a helping hand to native bees by avoiding “mulch madness” and landscaping with native plants. Most native bees (about 70%) are ground nesters, desiring bare, uncovered earth for nesting. Mulch gets in their way, as do lawns.
Ponder talked about some research on native bee plant preference. The researchers found that plants from South Africa, Australia, Central and South America are largely ignored by native bees, while a native like the California poppy will be visited by native bumblebees, sweat bees, and also non-native honey bees. I don’t doubt that research, but will note that the non-native wisteria on the front and back of my house are swarming with several species of bumble bees (most likely natives) when the flowers are in bloom, and when I had a blooming onion flower it was popular with natives as well as European honey bees. The rosemary plants at my office, however, only seems to attract honey bees, but that might be because the landscape managers at office parks love to cover any non-grassy ground with mulch and so the native bee population is low.
* An incredible fraction of fruit, nut and vegetable crops need assistance from bees. One study, “The Value of Honey Bees as Pollinators of U.S. Crops in 2000″ (PDF) from Cornell University (March 2000), estimated that almost $15 billion in crop value can be directly associated with honey bee pollination. A number of crops, including almonds, avocados, cranberries and onions are fully dependent on insect pollination (with the vast majority of those services provided by honey bees). Where bee populations have been wiped out, like in China’s southern Sichuan province, some farmers are trying to pollinate fruit trees by hand, as a 2007 episode of Nature called Silence of the Bees showed (the human-pollinator segment starts at 38:51). The video is no longer streaming on PBS, but is in the Netflix DVD collection.
** Only one other bee makes honey, that’s a stingless bee that is native to Central and Southern Mexico. Covered by Bayless in Episode 12 of Season 5 of Mexico—One Plate at a Time. The bees don’t sting, but that doesn’t mean you can go mucking around their hives to take their honey (which is used in the Yucatan to make a liqueur called Xtabentún). If you do, you’ll discover that they defend the hive by swarming the attacker and going into eyes, ears, mouth, and nose.