When was the last time you sighted a bumble bee? Photographed it?
It's National Pollinator Week and one of our favorite bumble bees is the yellow-faced bumble bee, Bombus vosnesenskii. It was also a favorite of internationally renowned bee expert Robbin Thorp, distinguished emeritus professor of entomology at the University of California, Davis, who passed away June 7 at age 85. (See obituary)
In fact, all bumble bees were his favorite, including the elusive Franklin's bumble bee, found only in a small range in southern Oregon and northern California and now feared extinct. We remember a July 2010 interview with 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.”
Thorp treasured bumble bees and encouraged everyone else to do so, too.
The yellow-faced bumble bees are native to the west coast of North America, from Baja California to British Columbia. They're important pollinators, especially important for their buzz pollination of tomatoes, peppers and cranberries. Buzz pollination occurs when they grab a blossom and shake it, dislodging the pollen. Honey bees can't do that.
The Xerces Society for Invertebrate Conservation recently posted that one quarter (28 percent) of North American bumble bees are in some degree of extinction risk. "Bumble bees face many threats including habitat loss, disease, pesticide use, and climate change." (See more information on bumble bees on the Xerces' site.)
Meanwhile, "across the pond," London has established a seven-mile long bee corridor of wildflowers just for pollinators.
"The Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES) said wild mammals had declined by 82 per cent since 1980, space for natural ecosystems had halved, and one million species were now at risk of extinction as a result of human action," according to a May 7, 2019 article in The Independent newspaper. "Insect pollinators are vital for the maintenance of ecosystem health and for global food security. Insects are required to maintain the existence of 75 per cent of crop species, 35 per cent of global crop production and up to 88 per cent of flowering plant species," reporter Harry Cockburn wrote.
Want to learn more about the bumble bees around us? A good start is to read these two books, both co-authored by Thorp in his retirement: Bumble Bees of North America: An Identification Guide (Princeton University, 2014) and California Bees and Blooms: A Guide for Gardeners and Naturalists (Heyday, 2014).
And, if you would like to get involved in citizen science, Bumble Bee Watch seeks your sightings.
Meet the competitors.
In this corner, meet Mr. Teddy Bear. He's a blond, green-eyed carpenter bee, Xylocopa varipuncta, a native, and one of three species of carpenter bees commonly found from northern to southern California to western New Mexico.
In the other corner, meet Mr. Bodyslam. He's a European wool carder bee, Anthidium manicatum, a native of Europe. His "immigrant ancestor" was first detected in the United States (New York) in 1963, and the species spread west. The carder bee (so named because the female "cards" fuzz from plants for her nest) was first recorded in California (Sunnyvale) in 2007.
The competitors meet on foxglove, Digitalis purpurea, which yields dramatic pink-purple fingerlike flowers (and medicine for heart patients).
Mr. Teddy Bear is famished. He's doing what entomologists call "nectar robbing." He's drilling a hole in the corolla and drinking nectar, bypassing the usual plant-pollinator relationship. He's grabbing the reward and "cheating" by entering the flower from the outside, avoiding contact with the anthers.
Mr. Bodyslam is territorial. He's patrolling the foxglove patch--HIS foxglove patch--trying to save the nectar for his own species so he can mate with them. When he sees intruders, he targets them.
So here's Mr. Teddy Bear, drilling and sipping, sipping and drilling. Life is good.
"Hey, get away from my flowers and nobody gets hurt! They're mine!"
"Hey, I'm bigger than you. Get lost."
And the battle begins.
The winner, in this corner, Mr. Teddy Bear. He successfully avoided contact by crawling between the flowers (where Mr. Bodyslam couldn't reach him) and then sneaking to the corolla.
But once--just once--contact erupted. Ouch!
It's the easy way to do it.
A carpenter bee heads for a foxglove blossom and drills a hole in the corolla to sip the nectar. This is "nectar robbing"--bypassing the pollination process and heading straight for the reward, the nectar.
Honey bees are quick learners. Soon they're sipping nectar from the hole pierced by the carpenter bee and they are not supplying "pollination services," either.
We all take shortcuts.
We look for the shortest line at the supermarket, we use keyboard shortcuts, and we text ”how r u?”
So, why shouldn't honey bees use shortcuts? They do.
If you've ever watched a carpenter bee drill a hole in the corolla of a tubed flower to get at the nectar—this is "nectar robbing" or bypassing pollination—you may have seen a honey bee come along and sip nectar from the hole. Why work hard to get at the nectar when it's right there for the taking?
This is the insect version of a convenience market!
Take the foxgloves (family Plantaginaceae, genus Digitalis). Sometimes you'll see a honey bee trailing or shadowing a carpenter bee that moves from corolla to corolla.
Short cut to the nectar!
Foxgloves, meet the European wool carder bee.
European wool carder bee, meet the foxgloves.
It's like "old home week" when these two get together. The plant (Digitalis purpurea) and the bee (Anthidium manicatum) are both native to Europe.
European wool carder bees, so named because the females collect or "card" leaf fuzz for their nests, were introduced in New York in 1963, and then began spreading west. They were first recorded in California (Sunnyvale) in 2007.
Honey bees (Apis mellifera) arrived in America 341 years before their cousins. European colonists brought the honey bee to America (Jamestown colony, Virginia) in 1622, but the honey bees didn't make it to California (San Jose area) until 1853.
Now they're together again, so to speak, but it's not a happy situation when a male wool carder bee spots a foraging honey bee.
Male European wool carder bees are very aggressive and territorial. They'll "bonk" other insects that land on "their" flowers such as lamb's ear, catmint and basil. They'll bodyslam honey bees, butterflies, sweat bees, carpenter bees, bumble bees and even a hungry praying mantis or an eight-legged spider (arachnid) or two. It's all about trying to save the floral resources for their own species so they can mate and reproduce.
One thing is certain: honey bees forage faster when those foxy male European wool carder bees buzz the garden.
They know each other well.