Category Archives: common misconceptions

Bad Bees Part I: Sex, Drugs, and Violence

Halictus sweat bee visiting Helminthotheca echioides (prickly ox tongue). (c) 2012 MRS All rights reserved.

Whenever I do education outreach, especially with small children, I like to paint a rosy picture of pollination. The bees and the plants help each other; the bee collects food from flowers, and in return they transfer pollen from the male parts of flowers to the female parts of flowers, which results in the production of seeds. We break out the cute fuzzy bee hand puppet and use velcro yellow balls (simulating pollen), which the kids can transfer from felt flower to felt flower.

When viewed in the visible light spectrum (left), this Mimulus flower looks uniformly yellow. However, when viewed in the UV spectrum (visible to bees- right), a dark arrow-shaped wedge points to the nectaries at the base of the flower.
source: wikipedia.org (Plantsurfer 2009)

When I talk with older audiences, I might portray a slightly racier scenario. After all, what is pollination other than flower sex mediated by a third party? In the photograph above, look at how tenderly the Halictus hooks its hind leg around the seductively curved stigma of the flower, at the profusion of pollen she has so carefully collected on the hairs of her hind legs to carry between flowers. Despite the more adult tack I use, I still tend to emphasize that this is a mutualistic engagement; the flower has evolved nectar and enticing patterns to seduce the bees, and in return the bees transfer pollen between plants. A nice example of this are something called nectar guides, or patterns in the UV spectrum (visible to bees but not to us) that guide bees towards the nectar reward in the flower.

And so the flowers grow. And so we get fruits and nuts and seeds. And so this green planet fluorishes.

As idyllic and parabolic as this picture may be, it brushes over a Machiavellian but more accurate version of how pollination (and evolution, for that matter) really works. In a way, I feel guilty teaching this airbrushed version of pollination because in some ways it may misrepresent how evolution and symbiotic relationships work in real life: as an escalating arms race.

In this darker world, flowers evolve to attract pollinators in order to increase reproductive fitness. In parallel, bees evolve to collect sugar rich nectar and protein rich pollen from flowers. As a byproduct, flowers feed bees and bees pollinate flowers, but this is not the purpose of the plant or bee, merely a byproduct of their concurrent actions.

And thus we enter the dark underbelly of the world of pollination, full of cheats and robbers and generally bad behavior. After all, it takes energy on the plant’s part to produce nectar and nutritious pollen, and pollen that is transfered by bees between plants is pollen that the bee cannot eat. If a bee can find a way to eat without pollinating, or a plant can find a way to be pollinated without feeding the bee, this may give them an edge over their competitors. One basic example of this that we see are bees that fastidiously clean all excess pollen off themselves before leaving a flower. Especially for a small bee, pollen can be quite heavy and make it more difficult to fly. By cleaning itself before takeoff, a bee can travel between flowers more easily but does not pollinate the next plant it visits.

Let’s take a look at the aspects of pollination I leave out of my classroom visits: the sex, the drugs, and the violence.

Sex and Drugs: The Cheating Orchid
The Bee Orchid preys on the sexual urges of male bees and wasps, luring them with drugs called pheromone mimics into a senseless orgy of failed mating. The flower copies in its shape, color, and texture a female bee or wasp. Furthermore, it entices males by releasing an intoxicating perfume: the smell of a female who is ready to mate. Hapless males converge on the flower and fight each other for the chance to attempt to mate. In the process, pollen packets called pollenia attach to the male. The next time it tries to mate with an ersatz bee, the pollenia make contact with the female part of the flower. In this scenario, the cheating orchid reaps all the benefits of pollination while the males get nothing but frustration and lost mating opportunities. For a great video of bee orchids in action (not to mention a rockin’ synthesizer soundtrack), check out this neat excerpt from Wild Orchids of Israel, filmed by Doron Hirschberg:

And Now for some Violence: Big Bad Carpenter Bees
Bees are no strangers to cheating at the pollination game, either. In my Xylocopa post, maybe you noticed that the gargantuan carpenter bees, rather than venturing into the trumpet-shaped structure of the sage flower, clutched onto the outside of the flower. Perhaps you even noticed a dark, drinking straw structure unfurled from the head of the bee and piercing into the flower through the side, rather than the front entrance.

Xylocopa robs the nectar from the an Autumn Sage (Salvia gregii) flower

The sage flower is designed for a pollinator to enter the main opening of the flower in order to reach the nectar. In the constricted petal tube, the bee must crawl past the anthers (pollen bearing structures) to reach the nectar, thus getting covered in pollen. This carpenter bee has other plans, however.

Using its heavily armored mandibles (used to chew through rotting wood to build nests), the carpenter bee rips a hole in the base of the petals, next to the nectar reward. It then sticks its proboscis in through the hole it has ripped, like a kid in a Tropicana orange juice commercial, and drinks the nectar without ever touching the anthers of the flower. The defenseless flower, once ripped open, is now vulnerable to other smaller bees that can use the hole made by the carpenter bee to access nectar directly. This process is called nectar robbing, because the flower is robbed of its nectar but reaps no pollination reward.

So the next time you go out to enjoy a pleasant Spring day, as you watch the industrious bees trundle from flower to flower, take a moment to reflect on the dark designs of both flower and bee. Although salacious and exploitative, I don’t like to think of this interplay in a negative light. To me, the complexity of coevolution makes this relationship more interesting, more beautiful, more strange than the boring stories we tell our children. This intricate biological world we live in operates by its own set of rules separate from Western human morality, and we have much more to gain by learning and appreciating these rules rather than placing value judgments on them.

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Plight of the Bumble Bee Part V: What I’ve Learned

Time to wrap up my Bombus segment. I hope that you enjoyed reading about the bumble bees and maybe even learned a couple things. I certainly did. A quick recap, a la “what I have learned:”

1. Our Southern Neighbors

In Plight of the Bumble Bee Part III: Not-So-Impossible-Giants, I posted this photo of a beautiful bumble bee I saw on a trip to Patagonia:

La Gigante Imposible (c) 2012 MRS

 

I mentioned that, while I was sure this bee was in the genus Bombus; (the bumble bee genus), I didn’t know which species it was.  Well just last week I stumbled across an article (incidentally also titled Plight of the Bumblebee so I guess I’m not as clever as I thought) that says there is only one bumble bee native to Patagonia, Bombus dahlbomii. This bee is the largest bumble bee in the world.

Our poor Southern neighbor appears to be suffering from similar issues to her North American cousins (see my post The Plight of the Bumble Bee Part IV: Pandora’s Bee Box, as described in this Science article.

2. Tricky Bee ID

The Mystery Bee Among the Blossoms

I was very flattered to receive a site visit from the highly esteemed Robbin Thorp of UC Davis, who happens to be the bee identification guru. He informed me that the conclusion I drew from my Is it a bumble? quiz, that the bee in question was most likely Bombus impatiens, was incorrect, and that the mystery bee was actually a male Eastern Carpenter Bee, Xylocopa virginica. The reason that the bee did not have any scopae (pollen collecting hairs) was because this individual was, in fact, a male (see The Dastardly Deeds of Male Bees, and while the male Eastern Carpenter Bee is often mistaken for the Common Eastern Bumble Bee, Bombus impatiens, certain aspects of the leg morphology can be used to tell them apart (for those of you keeping score, the hind tibia is swollen and shorter than the basitarsus).

In this blog, I will probably not be able to give positive identifications to a lot of the live bees I photograph. This is because I am still learning how to identify bees, and even for bee identification gurus, much of the time bees are nearly impossible to identify on the wing (the specimen must be taken for examination under a microscope). So I am always grateful to those wiser than I who are around to correct my mistakes. Thank you, Robbin Thorp!

Tune in next time for more photos of bees, large and small.

The Plight of the Bumble Bee Part II: What Gives a Bee its Bumble?

The bumble bee may be the most potent weapon in my arsenal when it comes to convincing people of the existence of bees other than honey bees. The conversation usually goes something like this:

Person at Party Feigning Interest in My Research: (after me explaining that I do not study honey bees) Oh wow, that’s so interesting. I always thought there was only one kind of bee.
Me: You probably know about more kinds of bees than you think. Like, what about bumble bees?
PPFIMR: …Oh yeah.

So what about bumble bees?

Bees on the Wing

Mystery Bee Among the Blossoms

Mystery Bee Among the Blossoms (c) 2012 CRT


My mom, who lives near Washington, D. C., sent me this photo of a bee visiting some of the famous Japanese cherry blossoms that encircle the Tidal Basin. She wanted to know if it was a bumble bee. With only a wing, an abdomen and part of a leg to go on, it’s hard to say, but let’s go over the evidence of what constitutes a bumble bee:

There are 250 described species of Bombus (bumble bees) worldwide. They are medium-sized to large, robust, furry bees. They can be distinguished from the similarly-large carpenter bees (Xylocopa) because carpenter bees generally have shiny, not furry, abdomens and hold their wings out to the side at rest (bumble bees neatly fold one wing over the other).

But the best way to tell if a bee is a bumblebee? It’s on the legs.

When female bees visit flowers, they have to collect pollen to feed all the little mouths back at the nest. Most females use long, shaggy hairs called “scopae,” often located on the hind legs, that look kind of like retro legwarmers.

Honey bees and bumble bees, however, collect pollen on special smooth, flattened structures called “corbicula.” The best way to think of a corbicula is as a tiny shopping basket that the bee fills with pollen to take home. Here’s a photo of a bumble bee’s corbicula from wikipedia.org:

Beatriz Moisset 2005


[an aside about corbicula: sometimes on really hot days during the field season, whenever I see a bumble bee, I start singing a song I like to call “Corbiculi, Corbicula,” which is sung to the tune of (surprise) “Funiculi, Funicula”. Hey, it helps keep me sane…]

So why am I confused by the Mystery Bee Among the Blossoms?

After I told my mom I wasn’t sure what kind of bee this was, she sent me this photo:

Want to test you bumble bee knowledge? Here’s a little quiz for you folks at home: is this bee a Bumble Bee or not?

Answer coming up next week…

The Plight of the Bumble Bee Part III: Not-So-Impossible Giants

In a speech in 2008, Mike Huckabee declared, “Aerodynamic engineers once figured out that… it is aerodynamically impossible for the bumble bee to fly. But the bumble bee, being unaware of these scientific facts, goes ahead and flies anyway.”

Creationists and other anti-science factions like to gleefully toss around this little tidbit. To them, this ridiculous notion underscores the folly of scientists, a useless, arrogant group that cannot prove anything of real value.

To these people, I will not mention vaccines, or computers, or electricity, or any of the other ways in which science has enriched their lives. I will not bring up the fact that while there are many phenomena unexplained by science, this doesn’t discredit the field, but rather gives job security to future scientists like myself. What I will say is that this idea that it is scientifically impossible for bumble bees to fly is, in fact, false. For some more details, here’s an article written by Cecil Adams, the self-described “world’s smartest human.”

During a 2010 trip to Punta Arenas, Chile, however, I caught sight of a bee so large that I had to admit its flight seemed an impossibility.

La Gigante Imposible (c) 2012 MRS

It’s a shame that there is no size reference in this photo. In the magical realm of memory, I seem to remember it being between the sizes of a jumbo gumballs and a table tennis ball. This bee, which, to the annoyance of my host, I kept referring to as “la abeja más grande que he visto,” is clearly a Bombus as evidenced by her large, fuzzy body; the wings folded across the back; and the smooth, flattened hind legs (or corbicula).

While I have not been able to ascertain the exact species of this bumble bee, from an informal communication I have learned that it is native to Chile. In recent years, populations these beautiful giants, as well as other bumble bees in North and South America, have been dwindling. Robbin Thorp, a bee expert from UC Davis, thinks that the main reason for these declines has to do with the use of domestic bumblee bee colonies to pollinate crops. Let’s hope that we will find ways to save these bumbling creatures so that they can continue their not-so-impossible flight for generations to come.

(c) 2012 MRS

Wait– domestic bumble bees, you say? Please tune in next week to hear about the practice of keeping bumble bees and how it might affect the natives.