Understanding cuckoo bumble bees: terrors or treasures?
Posted onFebruary 29, 2024byParker Smale|Bumble Bee Recovery, Native Pollinator Initiative, News and EventsPhoto: T. Harrison
What is the Bumble Bee Recovery Program? Since the 1990s, bumble bee numbers have been plummeting and that spells ecological disaster. Here at Wildlife Preservation Canada, we work to save at risk species of bumble bee from disappearing by monitoring them in the wild, breeding them for release at our conservation lab in Ontario, and studying their poop for parasites! We even host special community science events across the province to track population sizes, locate declining populations and provide hands-on training programs with the goal of expanding our efforts across Canada. We are the only organization in the country working to rebuild at risk bumble bee populations through conservation breeding.
Cuckoo bumble bees often get a bad rap, and, considering that some of Ontario’s at-risk bumble bees are cuckoos, it’s worth exploring why that is. To begin, let’s demystify what cuckoo bumble bees are all about. These bees are a bit like freeloaders in the insect world—they lay their eggs in other bumble bee nUnests and let the host colony do the parenting. Instead of building their own nests and raising worker bees, cuckoo bumble bees sneak into existing nests, usually causing the unfortunate demise of the host queen. Then, they enlist the help of the host colony’s workers to raise their own batch of offspring, which consists solely of males and new reproductive females. She and her offspring focus on egg-laying and reproduction, leaving foraging and childcare to the original queen’s workers.
(Left) A lemon cuckoo bumble bee. Photo: P. Smale. (Right) A Fernald cuckoo bumble bee female. Photo: C. Blair. Two of the five cuckoo bumble bee species in Ontario. Note the enlarged and curved stinger displayed here by the Fernald cuckoo.
Being lazy foragers
Since cuckoos rely on the workers form the host colony to do all of the foraging work, they’re able to ditch their corbiculae (concave sections of the hind leg surrounded in hairs that hold pollen that bees have collected; also known as pollen baskets) and invest in other, more dangerous adaptations!
Built for battle
Relative to their size, cuckoos boast larger and more curved jaws and stingers, turning them into formidable opponents. Their jaw muscles are also stronger than the average bumble bee, so they can bite harder!
Tough hided
Cuckoo bumble bees have thicker and sturdier sternites (the exoskeleton plates on the underside of the abdomen; the belly of the bee-st) compared to regular bumble bees, making them more resistant to harm. This allows them to more easily infiltrate bumble bee colonies without being seriously injured by angry workers.
Scent glands
Bumble bees have scent-producing glands called Dufour’s glands. In cuckoo bumble bee females, the substance inside may help her blend in as one of her host species or repel workers to discourage them from attacking her, with different species using different strategies.
Egg expertise
With more ovarioles (egg-producing parts of the insect ovary) and smaller eggs, cuckoo females are egg-laying machines, which helps streamline their takeover of a colony.
And yet, are murder machines not worthy of conservation? Of the five at-risk bumble bee species in Ontario, two of them are cuckoo bumble bees: Bombus suckleyi, the Suckley’s cuckoo, and Bombus bohemicus, the Ashton’s cuckoo. These bumble bees are inextricably tied to their hosts, some of which are at-risk themselves, and so monitoring cuckoo populations provides crucial insight into host populations. Moreover, predatory species like cuckoos are necessary regulators of their ecosystems, and so cuckoo conservation is essential to maintaining diversity in broader bumble bee communities.
The truth is that all organisms in an ecosystem, including predators and parasites, interact in complex ways to maintain a balance. Instead of trying to tip the scales when it comes to the inner workings of an ecosystem, conservationists try to focus on the larger, often anthropogenic (directly or indirectly caused by humans) threats facing species at risk: for bumble bees (of all kinds), these include pathogens and disease (spread from commercial bee colonies), agricultural pesticide use, habitat loss, and climate change. These threats are much larger than cuckoos are, and they’re threats we can address without potentially upsetting entire ecosystems.
The impacts of cuckoos and predators on bumble bee populations are miniscule compared to the impacts of their major threats: agricultural pesticide use, pathogen and parasite spread from commercial bee facilities, habitat loss, and climate change.
As we contemplate the coexistence of these intriguing bees, it is crucial to shift our focus towards addressing larger threats that jeopardize the well-being of bumble bees at large. Our organization is dedicated to bumble bee conservation, aiming to combat pressing issues such as pathogens, pesticides, habitat loss, and climate change. To join us in this vital cause, we invite you to explore our bumble bee conservation program and consider making a donation. Together, we can safeguard these essential pollinators and ensure the preservation of our ecosystems.
Parker Smale
Bumble Bee Lab Biologist – Bumble Bee Recovery Program
Parker came to WPC with a built-in passion for conservation breeding after experience rearing many types of insects. As the lead technician for WPC’s bumble bee breeding program, he specialized in data wrangling, pollen chefery, and entomological match-making. Now, as the program’s lab biologist, his focus is on refining rearing methods to improve conservation breeding outcomes: most recently, his work has contributed to the lab’s first successful yellow-banded bumble bee mating!
Recent articles on the project
We need your help