Head to the Bodega Bay in Sonoma County and you'll see little kids building sandcastles on the beaches.
But head to Bodega Head in the spring and summer, and if you're lucky, you'll see female digger bees—bumble bee mimics—creating their own versions of sandcastles. These bees, Anthophora bomboides stanfordiana, build their nests in the sandy cliffs.
Look for the evidence: nest holes and tiny turrets.
If you missed it, be sure to access KQED's Deep Look video on “This Bee Builds Sandcastles at the Beach” by Gabriela Quirós and crew. It's educational, informative and entertaining. The photography is superb.
An excerpt from the Deep Look video: “It might seem peculiar to see bees at the beach. But the bumblebee-mimic digger bee (Anthophora bomboides stanfordiana) makes its home at beaches in Northern California and Oregon. Once they've mated, the females spend the spring digging their nests into sandy cliffs overlooking the Pacific Ocean.”
“They find a nearby source of water like a stream and slurp water into a pouch in their abdomen called a crop. They can make 80 daily trips back and forth from the stream to a cliff onto which they spray the water to soften it up. This allows them to dig a series of holes into which they lay their eggs.”
This digger bee is sometimes called the “Stanford bumble bee digger,” because the subspecies name, “stanfordiana,” refers to the Stanford University collection from 1904.
What do they mimic? The yellow-faced bumble bee, Bombus vosnesenskii, native to the West Coast of North America. But unlike the female bumble bees, female digger bees rarely sting and are not defensive.
The late Robbin Thorp (1933-2019), distinguished emeritus professor of entomology at UC Davis studied these bees. Current researchers include community ecologist Rachel Vannette, associate professor, UC Davis Department of Entomology and Nematology.
Thorp frequently pointed out that when most people think of bees, they think of honey bees. But there's a great diversity in bees, as he wrote in a paper, “Biodiversity and Pollination Biology of Bees in Coastal Nature Preserves,” that he and colleague Thomas Gordon presented at the Proceedings of the Symposium on Biodiversity of Northwestern California, held Oct. 28-30, 1991 in Santa Rosa. “The world bee fauna of bees (superfamily Apoidea) is estimated at 20,000 species,” they wrote. “Of these, about 10% are social, 75% are solitary, and 15 % are cuckoo parasites of other bees (Bohart, 1970).
“Bees are most diverse and abundant in arid warm temperate areas of the world, especially in the Mediterranean, California, and adjacent desert areas (Michener 1979),” they wrote. “With rare exceptions, bees rely on nectar and pollen as food resources: nectar primarily as energy for flight and other activities, pollen as nutrients for reproduction (ovarian and brood development). Most bees are generalists when foraging for nectar, restricted primarily by body or tongue size. Many bee species, however, exhibit host-specificity (oligolecty) in relation to pollen resources (Robertson, 1925; Linsley, 1958). Linsley and MacSwain (1958) define oligolecty as the collection of pollen from one or a few closely related plant species by all members of a bee species with use of alternative sources occurring only during stress periods when such pollen sources are locally (or temporarily) absent.”
“Bees are ‘keystone' species in most plant communities because of their importance as pollinators for the reproductive continuity of many flowering plants including rare and endangered species,” they related.
We've seen the digger bees at Bodega Bay foraging on wild radish and lupine in the spring and summer. And building sandcastles the ocean waves can't reach and people generally ignore.
Last week we saw a family checking out the holes in the sandy cliffs. “What are these?” they inquired.
“Digger bees, bumble-bee mimics,” I responded, mentioning the KQED “Deep Look” video.
They said they'd watch it.
We have a feeling they'll be back next year to watch the bees build their sandcastles.
There's more to Sonoma County's Bodega Head than the stunning views, crashing waves, nesting seabirds, and bursts of flora and fauna.
The sand cliffs are also the home of a digger bee, a bumble bee mimic known as Anthophora bomboides stanfordiana.
"The species name indicates that it is a bumble bee mimic," the late Robbin Thorp, a global authority on bumble bees and a UC Davis distinguished emeritus professor of entomology, told us several years ago. "These bees need a source of fresh water nearby. Females suck up water, regurgitate it on the sandstone bank surface, then dig away at the soft mud. They use some of the mud to build entrance turrets, presumably to help them locate their nests within the aggregation of nests."
"The female," Thorp said, "sucks up fresh water from nearby, stores it in her crop (like honey bees store nectar) for transport to the nest. She regurgitates it on the sandstone, and excavates the moistened soil. She carries out the mud and makes the entrance turret with it."
On multiple trips to Bodega Bay over the years, we watch in fascination as the bees excavate their homes, zip in and out of their turrets, and nectar on nearby flowers.
This time (June 24) we photographed an ant and bee encounter on a turret. The ant? Formica transmontanis, according to ant specialists Phil Ward, professor of entomology at UC Davis, and UC Davis alumnus Brendon Boudinot, who recently received his doctorate from UC Davis, studying with Ward.
"The species nests on the bluffs," Ward told us.
And about that bee-ant encounter? Commented Boudinot: "I suspect the little lady was alarmed by the big bee. These ants and their relatives are rather passive scavengers except during the brooding season, when fresh meat is an order. Most entomeat for Formica tend to be free-walking insects than barricaded larvae, as probably for the bee. For these reasons I think that the encounter may be coincidental!"
Scores of UC Davis entomologists have engaged in research at Bodega Bay. Rachel Vannette, assistant professor, UC Davis Department of Entomology and Nematology, is currently researching Anthophora bomboides stanfordiana and its nests as part of a National Science Foundation grant. Her project on solitary bee provision microbiome includes investigating the diverse community of bacteria and fungi in the provisions and brood cells.
While COVID-19 mandates and precautions hamper her research team's efforts (she's done some preliminary sampling this year and the entire team is planning to do research next year), the digger bees of Bodega Head keep digging, crafting turrets, nectaring on the nearby flora--and encountering ants.
They're all in this together.
Have you ever seen a syrphid, aka hover fly or flower fly, that resembles a bumble bee?
Volucella bombylans is a fascinating fly that engages in identify theft. Of a bumble bee. It's a "wanna bee."
At first glance, it looks very much like a bumble bee, the Bombus melanopygus edwardsii, according to the late Robbin Thorp (1933-2019), distinguished emeritus professor of entomology at the University of California. Unlike a bumble bee, however, the fly has short stubby antennae and two wings instead of four. And, of course, it cannot sting.
Most of the species in the genus are inquilines, that is, they lay their eggs in bumble bee and wasp nests, and the larvae consume the host larvae.
We were fortunate to see a Volucella species recently in Vacaville. There's only one valid species of Volucella in North America, Volucella bombylans, according to Andrew Young, a postdoctoral fellow at the California Department of Food and Agriculture who addressed the UC Davis Department of Entomology and Nematology at a Feb. 5 seminar (pre coronavirus pandemic). "However, DNA evidence points to this being a species complex. So, I think it would be most accurate to call it Volucella bombylans complex right now."
If you have a chance, listen to Young's fascinating seminar, "The Natural History of Syrphidae: From Pollinators To Parasitoids." You watch it free here. Lynn Kimsey, director of the Bohart Museum of Entomology and UC Davis professor of entomology introduced him.
His abstract: "Syrphidae (Dlptera) is a species-rich family of true fly, with over 6200 described species worldwide," he says in his abstract. "Often known as flower flies or hover flies, syrphlds are likely the most significant group of pollinators outside of the bees--especially in Arctic climates. While research into their pollination-related behavior is still nascent, other aspects of flower fly biology have been relatively well-studied."
"Adults of many species are well-known for their impressive mimicry of stinging Hymenoptera, and known larvae display a degree of habitat diversity that is unusually broad for a single family of Diptera. Many larvae are predators on soft-bodied insects such as aphids, and therefore, show potential for crop-pest management, while others are aquatic filter-feeders that may have value in waste-management applications."
Young studied Syrphidae in the lab of Stephen Marshall, professor of entomology at the University of Guelph, Ontario, Canada. Marshall and Young are among the six co-authors of Field Guide to the Flower Flies of Northeastern North America" (Princeton University Press, 2019), a book described as "a groundbreaking guide to flower flies in North America."