There are a handful of places around the world with very high bumblebee diversity. Utah does not lead the list. In fact, it isn’t really all that noteworthy. In America, other mountainous states, like Montana and Colorado, have more species (Wilson et al., 2022). European nations also tend to have a higher diversity. And the mountains of Asia lead the list (Williams et al., 2010).
But Utah bumblebees are unique in at least one way. There are more orange-banded species here than anywhere else (comparing places of comparable size). This orange-banding refers to the top side of the visible abdomen where the coloring is strikingly visible from above. Along with the typical bumblebee colors of yellow, white and black, we have 9 species that have orange banding. The color is not always in the same place. Sometimes it is wide and located noticeably between thin yellow bands. Sometimes it is narrower or shows up at the end of the abdomen. Sometimes only on the sides. But these 9 species represent 90% of all the orange-colored species in America.
It would be nice if we could somehow make a connection between this coloring (of bees) and the beautiful red-rock geology - where many of these bees live. The colors are often similar, but the connection is probably far-fetched. Our bumblebees (of any color) tend to nest in (or on) the ground and visit flowers of many colors. They seem to completely ignore the orange erosional landscape all around. It is more likely that the orange theme developed for the protection it offers and not, as my wife Kathy would say, because they are color coordinated.
The natural world is full of species that resemble each other (we call this mimicry) - or that resemble details of the places they live (we call this camouflage or protective resemblance). When I was in school, I learned that monarch butterflies are bitter-tasting to birds because they feed on milkweeds that are also bitter (and that have heart poisons in their bodies from the milkweeds). I also learned that viceroy butterflies, even though they are not bitter, are also protected because they look like monarchs and the birds are unable to tell them apart.
This is classical mimicry where one species is poisonous and one is not. But it is only one kind of mimicry. We call it Batesian mimicry (after Henry Walter Bates who first noted it in butterflies in Brazil). Our bumblebees don’t follow this pattern. As far as we know, each of the orange-banded species is capable of stinging a predator. The word we use for this form of resemblance is Müllerian mimicry (named after Fritz Müller), where all of the species are “honest” about their warning colors. None of the bumblebees are free riders.
Scientists believe that the orange banding evolved as a protection against predation. Bright reds and oranges are commonly seen in species that have chemical or mechanical means of defending themselves. Predators tend to leave them alone. With Müllerian mimicry each of the species contributes to the overall message.
In one of our species (the Vancouver Island Bumblebee) the orange banding is evolving right now. This species is recognized by the black V-shaped area on the thorax and is a common visitor to meadows at mid and higher elevations throughout the Western United States. Outside of Utah it is mostly yellow and black. But here in Utah there seems to be an advantage in having an orange-band - in having access to some of that Müllerian protection. Here most of the populations of the Vancouver Island Bumblebee have evolved the orange banding.
The story in Utah gets even more interesting because we have insects that mimic the Müllerian mimics themselves. I recall one afternoon in late June. I was working with a few students on a project just a few miles up Cedar Canyon (east of Cedar City). We were sampling pollinators at a beautiful meadow called Crystal Spring. There were three different kinds of orange-banded bumblebees in the area. And we were looking for some of their nesting sites. Then one of the freshman students said she had just caught a bumblebee that she didn’t recognize. It was in her insect net and she didn’t feel comfortable removing it.
She was quite surprised when I told her the insect she was holding was not a bee at all. It was a fly. It was a large robber fly (of the aggressively predatory family Asilidae). These flies are known to attack other insects, even catching other bees out of mid-air. The one in the net belonged to the genus Laphria and it was colored bright orange and yellow, and it was the same size as the bumblebees (though a bit narrower).
A few minutes later, one of the other students showed me yet another fly mimic. It was a hover fly (specifically a drone fly) with the same colors and the same overall shape. Drone flies are not dangerous - at least not to predatory birds. They have predatory larvae that eat small soft-bodied insects like aphids. But they were certainly not (as orange-colored adults) contributing to the so-called “ring” of Müllerian mimics. It appeared to be a free rider - a Batesian mimic among the group of otherwise honest mimics.
Mimicry is woven deep into the world. We find it in the velvet coating of a bee, for sure, but also in the calling of a mockingbird and in the banding of a snake. It can even show up in behavior and in speech. A human child watches carefully the actions of her friends, and mimes her way into becoming a human being.
We as a species have greatly magnified our options. We change our clothes to satisfy a whim, with wardrobes more convincing than a cuttlefish’s blush. We want our choices to be new and we want them suited just for us. And yet we copy from the advertiser’s many tempting offerings. We play with and modify our mimicry every single day.
Is the mimicry that protects a tasty butterfly similar to our own sartorial choices? Or do we change ourselves for other ends? The orange-banding of a bee is very much a part of its identity. It isn’t a form of protective camouflage. The coloring is intended to send a message to enemies. It is also a token of membership.
There is insight here and irony even if we don’t know all the answers. We, as a species, seek for popularity and acceptance in a brand, even as we try to be unique. Nature, on the other hand, is not concerned with being seen unless she is out looking for a mate. Evolutionary biologists argue that this is not different from us. But what is different is our indecision and our many choices. Sometimes we want to be camouflaged or hide. Other times we want to be seen. Very often we want to be a part of a group. Other times we pretend to be other than we are. We seem to be unique as a species in the extent of our imagination, including the many creative ways we are able to see ourselves - and even to create ourselves.
The colors of bumblebees and humans are beautiful and fascinating. But there is a difference between us. The colors of a bee are inherent, that is they are genetically determined. Our decisions are often optional even though the underlying biological needs that lead us to be creative are not optional. They are inherent and deeply programmed needs. Becoming who we want to become is the quest of a lifetime that requires our creativity even as we come to understand our deeper mental and physical realities.
And color does not change the fact that there are many other aspects of our nature. We should not assume that membership in a mimicry ring automatically provides immunity to bees. Much to the contrary. Bumblebees have a lot going on in their lives and the challenges of survival come from a lot of different directions and at different times of the year.
Winter is one of their biggest challenges. It is also one of their most important competitive advantages. Bumblebees are most abundant and in greatest diversity on mountains and in the north. There are a lot of pollinators in the cactus gardens of the Southwest, hundreds of different kinds. And most of them are bees, just not bumblebees. But things change as you go up a mountain. The pollinators are not the same species. Bumblebees gradually become more important. If you go high enough, even the flies become more important to flowers than most bee species.
Scientists have known this for a long time. It’s one of the reasons that bumblebees are so endearing to those of us that love mountains - and to those of us that live in mountainous regions. It’s easy to just assume that bumblebees are the thick furry grizzlies of the insect world. They enjoy the summer meadows and simply hibernate through the cold months of the year. But this picture is in need of nuance.
Late fall and winter are the seasons of bumblebee death. They do not survive the winter by huddling into groups like honey bees in order to keep from freezing. Very often the smaller workers just succumb to the cold. It is only the larger queens that survive into spring. And it is their ability to generate and insulate heat with their large thoracic muscles that give them this advantage. If they are unlucky or otherwise choose poor overwintering sites, even the queens may not survive. Color has nothing to do with it.
And then there are the parasites. In Utah, these tend to be other bumblebees. The most commonly encountered species has the rather lengthy name of Indiscriminate Cuckoo Bumble Bee (Bombus insularis). Some authors call them social parasites. Sometimes they are called kleptoparasites. They don’t feed on the bodies of other bees, instead they steal their food and lay eggs for other bumblebees to take care of and raise.
Sometimes they will fight for the food and these fights can be lethal. They always cause stress among the host bees. I have hiked on hundreds of Southern Utah trails over several decades and, during some years, I find this parasitic bee to be quite common. It has a black abdomen with a pale white fringe on its back end. Unlike other bumblebees that have a special hair-free space on their hindlegs for storing pollen, cuckoo bumblebees don’t bother with the task of gathering this protein-rich food for their brood, and they don’t have this anatomical storage capacity. They just follow other bees into their nests, fight anyone who stands in their way and then lay eggs that the host bees take care of. I am always tempted to get rid of some of them in order to give the other bees a break. Sad to say, I sometimes give in to temptation.
Other parasites and pathogens can be a problem to bumblebees. Scientists worry about a process called spillover. This happens when a disease jumps species. In America, there are a handful of these harmful organisms that already afflict honeybees or imported bumble bees - especially in agricultural areas. Ivan Meeus et al. (2011) have compiled a list of parasites and pathogens that are likely candidates for spillover events into populations of native American bumblebees. These organisms include six kinds of viruses, two fungal pathogens, two arthropods, two euglenozoans, and a species of Apicomplexa.
Almost every year we learn of bumblebee declines due to these harmful organisms. Most of the time the problems are caused by human ignorance and negligence. And most of the time, the problems occur around large greenhouse operations or in blueberry farms. This doesn’t really apply to Utah and we do not suffer from these problems as much as other places because we live in a high desert and/or mountainous state that is largely free of bumblebee diseases. Two species that are suffering declines in surrounding areas (the Western Bumble Bee and Morrison’s Bumble Bee, for example) are holding their own in Utah.
Nature is dealing with our changing world in a lot of different ways. And one of her greatest challenges is the increased rate of these changes. The changing colors of the two-form bumblebee in Utah has likely been happening for thousands of generations. The sudden appearance of diseases and of changing habitats is happening in just a few.
When I watch a Utah meadow and see the evidence of a world developing on its own - becoming so colorful even as it remains interdependent - I wonder why our own creativity can be so harmful. Why do our greedy and desperate natures prevail so often when we have the capacity to become orange with the bees? Maybe part of the reason is that we have never discovered all the different forms and how we are not so different after all. Maybe we should dress more like the bees.
If you ever happen to visit our state (or even if you live here and don't get out much) pay attention to our big furry bumblebees. They are still here - lots of them - and they keep protecting our world even as they work together to protect themselves.
References
Ghisbain, G., Lozier, J. D., Rahman, S. R., Ezray, B. D., Tian, L., Ulmer, J. M., ... & Hines, H. M. (2020). Substantial genetic divergence and lack of recent gene flow support cryptic speciation in a colour polymorphic bumble bee (Bombus bifarius) species complex. Systematic Entomology, 45(3), 635-652.
Heinrich, B. (2004). Bumblebee Economics. Harvard University Press, Cambridge, Massachusetts.
Meeus, I., Brown, M. J., De Graaf, D. C., & Smagghe, G. U. Y. (2011). Effects of invasive parasites on bumble bee declines. Conservation Biology, 25(4), 662-671.
Plath, O.E. (1934). Bumblebees and their Ways. Macmillan Company, New York.
Williams, P. H., Ito, M., Matsumura, T., & Kudo, I. (2010). The bumblebees of the Nepal Himalaya (Hymenoptera: Apidae). Insecta Matsumurana. New series: journal of the Faculty of Agriculture Hokkaido University, series entomology., 66, 115-151.
Wilson, J. S., Pan, A. D., Alvarez, S. I., & Carril, O. M. (2022). Assessing Müllerian mimicry in North American bumble bees using human perception. Scientific Reports, 12(1), 17604 (9 pages).
