Cuckoo Bees

Cuckoo bees: Indiscriminate Cuckoo bee Courtesy & © Mark Brunson, Photographer
Indiscriminate Cuckoo Bee
Courtesy & © Mark Brunson, Photographer

Indiscriminate Cuckoo bee Courtesy & © Mark Brunson, PhotographerIndiscriminate Cuckoo Bee
Courtesy & © Mark Brunson, Photographer

I’d like to tell you a crime story. At least, it would be a crime story if told from a human perspective. But is it still a crime story if it’s about the natural world? I’ll tell it and then let you decide for yourself.

First let me set the stage: Not long ago I was hiking in Northern Utah’s Bear River Range. It was the height of wildflower season, and I was enjoying the colorful variety of blossoms along the trail. I stopped to admire a tall, showy plant with dozens of purplish-green blossoms: Frasera speciosa, commonly known as monument plant or green gentian. It’s often seen near the top of Logan Canyon, but what struck me about this particular monument plant was that it was full of bumble bees.

I knew that a Utah-based conservation science organization, Sageland Collaborative, is asking community volunteers to help them measure bumble bee diversity in the state, so I took out my phone and snapped a few photos. Later I uploaded the best photos into an app called iNaturalist so they’d end up in the Utah Pollinator Pursuit database maintained by the Utah Division of Wildlife Resources with Sageland’s help. Then I waited to learn what species of bumble bee I’d seen. The answer came back: indiscriminate cuckoo bumble bee. I thought: What an unusual name. I needed to know more.

It turns out “indiscriminate” simply means that, unlike many native bees that are particular about what they eat, this species doesn’t much care where it gets its nectar. As for “cuckoo”? Like the birds they’re named after, these bumble bees are thieves.

Or to say it more scientifically: these bumble bees are kleptoparasites. Parasites – animals that take resources they need from other species to the detriment of those species – and “klepto,” as in stealing. Like cuckoos or cowbirds, they lay their eggs in the nests of other bumble bee species, letting the workers from the host species do the work of raising them.

Here’s where our crime story gets even more sinister. When a cuckoo bumble bee queen finds a suitable nest to rob – one with a good-sized group of workers to raise the bee larvae, but not so many workers that they can easily protect their queen – she kills the host queen and becomes part of the colony, laying her alien eggs for the host workers to feed.

Cuckoo bumble bees don’t need their own workers, so they’re less often seen on wildflowers. In fact, there’s a good chance that some of the other bumble bees on my monument plant – the ones I didn’t get a picture of – were members of the host species. They also don’t need to take pollen back to a nest of their own, so they don’t have those “pollen baskets” we often see on the hind legs of female bumble bees.

But they do move pollen from flower to flower when it sticks to their bodies as they feed. In other words, they do play a role in sustaining the wildflowers we enjoy every summer. So is this really a crime story? Or is it just another example of the amazing diversity of behaviors found in nature? While you’re deciding about that for yourselves, I hope you get a chance to enjoy watching Utah’s various kinds of bumble bees as they do their all-important work.

I’m Mark Brunson, and I’m wild about Utah’s native bees.

Credits:

Images Courtesy & Copyright Mark Brunson, Photographer
Featured Audio: Courtesy & © Kevin Colver, https://wildstore.wildsanctuary.com/collections/special-collections and J. Chase and K.W. Baldwin. https://upr.org/
Text: Mark Brunson, https://www.usu.edu/experts/profile/mark-brunson/
Additional Reading: Lyle Bingham, https://bridgerlandaudubon.org/

Additional Reading

Wild About Utah pieces authored by Mark Brunson

Sheffield, Cory S., Cuckoo bees, Epeoloides pilosula, The Xerces Society, https://www.xerces.org/endangered-species/species-profiles/at-risk-bees/cuckoo-bees

Smale, Parker, Understanding cuckoo bumble bees: terrors or treasures?, Wildlife Preservation Canada, February 29, 2024, https://wildlifepreservation.ca/blog/understanding-cuckoo-bumble-bees-terrors-or-treasures/

Barth, Amanda, The Unique Lives of Cuckoo Bees, Sageland Collaborative, July 25, 2024, https://sagelandcollaborative.org/blog/2024/7/25/the-unique-lives-of-cuckoo-bees

Bumblebee Queens of Spring

Bumblebee Queens of Spring: Bombus bifarius. Copyright (c) 2008 Don Rolfs
Bombus bifarius,
Copyright © 2008 Don Rolfs

This is Linda Kervin for Bridgerland Audubon Society.

When crocuses are pushing through the snow in your garden, you might see another sign of spring: the flights of bees. Other bees may fly in spring, but few are as early or as boisterous as bumble bees. Utah is home to more than a dozen species of bumble bees, all of who belong to the genus Bombus (which in Greek means buzzing). All have a combination of black and yellow markings on their bodies. Some also have orange bands. Unlike honey bees that pass the winter warmly clustered in hives, bumble bees overwinter as solitary queens, dormant under a few inches of loose soil or leaf litter. These queens are quiescent all winter until warming soil beckons their reawakening to start their colony.

From March to May, watch for a behavior called nest searching, when the big, burly queen bumble bees fly low over the ground, stopping often to investigate holes in the earth or in building foundations. Bumble bees nest in small, insulated cavities, such as abandoned rodent burrows or bird houses. Once the queen finds a suitable nest site, she is out and about, foraging for pollen and nectar to provision her offspring. After a few days she will have sufficient food to begin laying eggs. Like all bees, her offspring progress through four life stages: egg, larva, pupa and adult. In just under a month, her daughters develop into adults, each chewing free of its cocoon.

Bombus griseocollis Queen
Foraging on Hedysarum
Copyright © 2008 Jamie Strange

These daughters take over foraging and nest construction duties, leaving the queen to remain in her nest and continue to lay eggs and incubate her brood. Workers are often much smaller than their mother, so don’t expect to see many big bumble bees again until autumn, when next year’s queens start the cycle anew, searching for mates and a spot to spend the winter.

This is Linda Kervin for Bridgerland Audubon Society.

Credits:

Photo: Courtesy & Copyright © 2008 Don Rolfs & Jamie Strange

Text: Jamie Strange, USU USDA-ARS Pollinating Insect Research Unit

Additional Reading:

ID a Bumblebee, https://www.ars.usda.gov/Services/docs.htm?docid=10749

Bumblebee Watch, https://www.bumblebeewatch.org/
Bumble Bee Watch is a citizen science project through the partnership of The Xerces Society, the University of Ottawa, Wildlife Preservation Canada, BeeSpotter, The Natural History Museum, London, and the Montreal Insectarium.