The news is disturbing but not unexpected.
Scientists are linking global climate change to one reason why the worldwide population of bumble bees is declining.
An article published Sept. 28 in the journal Ecology Letters by Florida State University (FSU) researchers showed that bumble bees just aren't getting enough floral resources.
For the study, lead researcher and postdoctoral fellow Jane Ogilivie and six colleagues examined three subalpine bumble bee species in Colorado's Rocky Mountains, and found that the changing climate means fewer flowers.
"Knowing whether climate variation most affects bumble bees directly or indirectly will allow us to better predict how bumble bee populations will cope with continued climate change," Ogilivie told the FSU News Service in a press release. "We found that the abundances of all three bumble bee species were mostly affected by indirect effects of climate on flower distribution through a season."
The FSU News Service aptly headlined the research a "Stinging Report."
"When researchers think about flower effects on bees, they typically consider floral abundance to be the most important factor, but we found that the distribution of flowers throughout a season was most important for bumble bees,” Ogilivie said. “The more days with good flower availability, the more bees can forage and colonies can grow, and the bigger their populations become. We now have longer flowering seasons because of earlier snowmelt, but floral abundance has not changed overall. This means we have more days in a season with poor flower availability.”
The researchers wrote in their abstract: "Climate change can influence consumer populations both directly, by affecting survival and reproduction, and indirectly, by altering resources. However, little is known about the relative importance of direct and indirect effects, particularly for species important to ecosystem functioning, like pollinators. We used structural equation modelling to test the importance of direct and indirect (via floral resources) climate effects on the interannual abundance of three subalpine bumble bee species. In addition, we used long-term data to examine how climate and floral resources have changed over time. Over 8 years, bee abundances were driven primarily by the indirect effects of climate on the temporal distribution of floral resources. Over 43 years, aspects of floral phenology changed in ways that indicate species-specific effects on bees. Our study suggests that climate-driven alterations in floral resource phenology can play a critical role in governing bee population responses to global change."
Bumble bee expert Robbin Thorp, distinguished emeritus professor of entomology at the University of California, Davis, long ago sounded the alarm that bumble bees are in trouble. He is the co-author of Bumble Bees of North America: an Identification Guide (Princeton) and California Bees and Blooms: A Guide for Gardeners and Naturalists.
The last bumble bee we saw--the last of the season--was on Sept. 23 at Kate Frey's pollinator garden at the Sonoma Cornerstone, Sonoma. It was a yellow-faced queen bumble bee, Bombus vosnesenskii, nectaring on a spiked floral purple plant, Salvia ‘Indigo Spires' (Salvia farinacea x S. farinacea). The queen had apparently emerged from hibernation to find food on that warm summerlike day.
I knelt to capture some images.
"Oh, it's just a bumble bee," scoffed one tourist, casually sipping a glass of wine. "They're everywhere."
Sadly, they're not.
Hey, honey bee, I'll race you to the flowers.
Okay, but you'll lose. I can go faster. Watch me!
The scene: a male bumble bee, Bombus melanopygus, and a worker honey bee, Apis mellifera, are buzzing along at breakneck speed toward the lavender in our pollinator garden in Vacaville, Calif.
They nearly collide but Mr. Bumble Bee pauses in mid-air and gives Ms. Honey Bee a free pass---and just in time for National Pollinator Week, when all of our pollinators need free passes! That starts out with two crucial steps: plant bee-friendly flowers and avoid using pesticides. Feed them food, not poison.
The end result here: plenty of nectar for everyone.
Bombus melanopygus, also known as the black-tailed honey bee, is among the bumble bees featured in the book, Bumble Bees of North America: An Identification Guide (Princeton University), the award-winning work of Paul H. Williams, Robbin W. Thorp, Leif L. Richardson and Sheila R. Colla.
Thorp, a distinguished emeritus professor of entomology at UC Davis, is also the co-author (along with Gordon Frankie, Rollin Coville, and Barbara Ertter) of California Bees and Blooms: A Guide for Gardeners and Naturalists. They offer great information on bee identification, but also crucial advice on how to attract and retain bees in your garden.
Happy Pollinator Week!/span>
Arthur Shapiro, distinguished professor of evolution and ecology at UC Davis, annually sponsors the "Beer for a Butterfly" contest, offering a pitcher of beer for the first cabbage white butterfly (Pierae rapae) of the year found in the three-county area of Sacramento, Yolo and Sacramento. He launched the contest in 1972 as part of his long-term studies of butterfly life cycles and climate. This year he again won the contest; he collected a newly eclosed butterfly at 1:56 p.m. Thursday, Jan. 19 near the Solano Park Apartments on the UC Davis campus.
But where's the first bumble bee of the year in the Yolo county area?
At 2:02 today (Friday, Jan. 27) naturalist and insect photographer Allan Jones of Davis alerted us: "Two Bombus melanopygus on manzanita just east of the redwood grove (UC Davis Arboretum)."
And then he found another melanopygus. It was a three-in-one day.
The story behind the story: five years ago, a small group of keen-eyed bumble bee aficionados (Robbin Thorp, distinguished emeritus professor of entomology at UC Davis and co-author of Bumble Bees of North America: An Identification Guide; and three naturalists and insect photographers Gary Zamzow and Allan Jones of Davis, and yours truly of UC Davis) launched our own contest.
In an unusual twist, Jones found both genders at the same time. After finding and photographing two males just east of the Arboretum's redwood grove, he spotted and photographed a female just west of it.
"Surprising to see males this early in the season," noted Thorp, who co-authored the book, California Bees and Blooms: A Guide for Gardeners and Naturalists. "Unusual to see males before any workers are on site. Could be from a gyne that overwintered but was not mated before she went into hibernation; or maybe the sperm she received were not viable; or maybe she was unable to release sperm from her spermatheca to some eggs as they passed through her reproductive tract."
"At any rate," Thorp told Jones, in congratulating him, "you got two firsts for the season at one time."
Great job, Allan Jones! And the bumble bee season begins...
Thorp, a noted bumble bee expert, hasn't seen Franklin's bumble bee for 10 years, but that doesn't mean it's not there--somewhere in its small native range of southern Oregon and northern California.
Thorp, distinguished emeritus professor of entomology, UC Davis Department of Entomology and Nematology, and co-author of Bumble Bees of North America, An Identification Guide, has been chasing Franklin's bumble bee (Bombus franklini) since 1998, the year he began monitoring for the elusive bee.
Last August a documentary crew from CNN chased him--well, sort of. They followed him to a meadow near Mt. Ashland, Oregon, where he last saw the bumble bee on Aug. 9, 2006.
John Sutter, a columnist for CNN Opinion who focuses on climate change and social justice, wrote about Thorp, then 82, in a piece he called "The Old Man and the Bee," a spinoff of Ernest Hemingway's "The Old Man and the Sea."
Sutter said he had no problem identifying Thorp. "White truck, bumble bee stick on tailgate. Yep, that's him."
Thorp also wore a t-shirt with an image of Franklin's bumble bee, a gift from his daughter. It's an image he took.
"That black-and-yellow bee, which looks like so many others except for the characteristic 'U' on is back, is the object of Thorp's obsession," wrote Sutter. "It's a creature he told me flies through his dreams always just out of reach."
No, Thorp and the documentary crew didn't find it that August day. Other bees, but not "that one."
But Thorp will keep looking for Franklin's bumble bee, which is on the Red List of Threatened Species of the International Union for Conservation of Nature and Natural Resources (IUCN). He helped sound the alarm that put it on the Red List.
"Bombus franklini occurs only in the USA," IUCN relates. "It is found only from southern Oregon to northern California between the Coast and Sierra-Cascade Ranges, in Douglas, Jackson and Josephine and Siskiyou and Trinity counties in Oregon and California, respectively. This area is around 190 miles in the north-south direction (40º58' to 43º30'N latitude) and 70 miles from east to west (122º to 124ºW longitude)."
Franklin's bumble bee was named in 1921 for Henry J. Franklin, who monographed the bumble bees of North and South America in 1912-13. During its flight season, from mid-May through September, Franklin's bumble bee frequents California poppies, lupines, vetch, wild roses, blackberries, clover, sweet pea, horsemint and mountain penny royal. It collects pollen primarily from lupines and poppies, and gathers nectar mainly from mints.
We remember a July 2010 interview with Robbin Thorp.
“People often ask the value of Franklin's bumble bee," Thorp told us. "In terms of a direct contribution to the grand scale of human economies, perhaps not much, but no one has measured its contribution in those terms. However, in the grand scheme of our planet and its environmental values, I would say it is priceless.”
“Loss of a species, especially a pollinator, diminishes our global environment,” he said. “Bumble bees provide an important ecological service--pollination. This service is critical to reproduction of a huge diversity of plants that in turn provide shelter, food (seeds, fruits) to diverse wildlife. The potential cascade of effects from the removal of even one localized pollinator may affect us directly and indirectly.”
Meanwhile, Thorp continues to receive photos from folks asking if "this one" is Franklin's bumble bee. Or "that one."
No. Not "this one." Or "that one."
But he appreciates the lookout.
And Robbin Thorp still holds out hope that somewhere in that five-county area of southern Oregon and northern California, Franklin's bumble bee may reappear. Maybe 2017?
After all, it's a brand new year.
We remember seeing a varroa mite attached to a foraging honey bee one warm summer day in our pollinator garden. The mite was feeding off the bee and the bee was feeding on the nectar of a lavender blossom.
Didn't seem fair.
We've never seen a varroa mite on bumble bees or carpenter bees, but Davis photographer Allan Jones has--and he's photographed them. (See below)
When varroa mites tumble off a honey bee and into a blossom, they can hitch a ride on other insects, such as bumble bees and carpenter bees.
"Varroa have been recorded hitching rides on bumble bees and yellowjackets," observed native pollinator specialist Robbin Thorp, distinguished emeritus professor of entomology at UC Davis. "Varroa have been reported as feeding on larvae of these and other critters--but not successfully reproducing on them. Also bumble bees and yellowjackets typically overwinter as hibernating queens not as perennial colonies like honey bees. Thus they are not suitable hosts for Varroa."
Extension apiculturist emeritus Eric Mussen says that bees other than honey bees aren't reproductive hosts for the varroa mite.
"As far as I know, Varroa destructor may be able to find soft areas of the exoskeleton of insects other than honey bees and feed on them," he says. "I have no idea whether or not the substitute hemolymph would sustain the mites for very long. The mites have practically no digestive capabilities. They simply utilize the previously-synthesized bee blood, to which they seem to be perfectly adapted."
"Since the mites reproduce on honey bee pupae, there are a number of considerations about potential other reproductive hosts," Mussen said, citing:
- Are the nutrients of the substitute host close enough to those of honey bees to support immature mite development?
- Can immature mites that develop properly at honey bee cell environmental conditions (temperature and relative humidity) find a similar environment in the nests of other insects?
- Do other insects tolerate the presence of mites on their bodies or in their brood nests?
Like honey bees, bumble bees do segregate their pupae in single cells, Mussen says, but he was unable to find any studies devoted to whether bumble bee pupal conditions support Varroa destructor reproduction.
Sounds like a good research project!