Category Archives: Halictus

Intimate Portraits of Bees by Sam Droege

Female striped sweat bee, Halictus ligatus, dusted in pollen. Photo by Sam Droege of the USGS, click to visit full article

Female striped sweat bee, Halictus ligatus, dusted in pollen. Photo by Sam Droege of the USGS, click to visit full article

Anyone who studies native bees in North America knows about Sam Droege, in no small part due to his stunning closeup photographs of bees.

Learn more about Sam Droege, his work with bees, and the beauty of bee diversity in a recent feature article by National Geographic

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The Little Things: An Entomological Perspective

Male sweat bee (probably Halictus tripartitus) on mustard plant. (c) 2012 MRS All rights reserved.

This past Labor Day weekend, I went on a camping trip with my in-laws to Big Sur. Some people go to Big Sur with a copy of Dharma Bums in their back pockets. Other people go there to take in the beauty of the landscape and the fresh sea air. Still more people visit to retreat into the stillness of the redwood forest. Nearly all have digital cameras slung around their necks, ready to capture the beauty of the moment. But while you can find most tourists crowding around the railing to take majestic photos of things like this:

You can always pick out the -ologists because we are foolishly squatting, blocking the trail, taking photos of bugs and weeds:

(c) 2012 MRS

A cloud of these little guys, so small that they could easily be mistaken for small flies, were swarming the weeds on the side of the trail. Based on the length of the antennae, the striping of the abdomen, and the color of the legs, I am betting they are male sweat bees (Halictus tripartitus). While male bees typically come out earlier in the season than females (see The Dastardly Deeds of Male Bees), Halictus tripartitus males arrive on the scene later in the season than the hardworking females. This is because sweat bees are social, with a single female waiting out the Winter and founding a nest (complete with workers, drones, and future queens) in the Spring. Because the first generation of offspring she produces are entirely female workers (it’s a lot of hard work to establish a nest), there is no point in laying male eggs until later. Remember: male bees are pretty much useless except for mating. So in late Summer/early Fall, once the party has been long over for most bee species, we see swarms of these late arriving sweat bee males, looking for action.

Pollen grains under a SEM microscope (Dartmouth Electron Microscope Facility, Dartmouth College)

We are fortunate to live in a reality in which beauty surrounds us on all scales, from the microscopic pollen grains sticking to the hairs of the bee to the vast ocean serving as a backdrop to the scene. Our interests and backgrounds often shape the focus and scale in which we perceive this beauty. One of the great pleasures in my life has been learning how to appreciate the world in different ways, from landscapes to plants and insects to human art forms. This blog acted as a vehicle for me to share one way in which I perceive beauty in this world. It has been a lot of fun for me, and I hope that you are enjoying it as well. Thanks for reading!

Mimulus sp.. (c) 2012 MRS All rights reserved

A Closer Look at Sweat Bees (Halictidae)

Sweat bees have been weighing on my mind lately. I stumbled across this post, which I thought was well written and informative. I hope you enjoy it as much as I do.

ferrebeekeeper

Sweat bees are tiny bees of the family Halictidae.  They take their common name from their affinity for human sweat, which they lap off of our naked skin for the salts and electrolytes therein. Sweat bees are small (at least to us) and tend to measure between 3 and 10 millimeters in length. A few species have thick robust bodies, but most are slender and delicate.  They tend to be glossy black, but some have exoskeletons which are gorgeous shades of metallic gold, green, purple, or blue.

The majority of sweat bee species nest in the ground (although a few build their homes in dead trees).  The social behavior of sweat bees runs the entire gamut of bee conduct: the University of Florida Department of Entomology Website states, “species can be solitary, communal, semi-social, or eusocial.”  Sweat bees therefore greatly interest entomologists who are studying the development of eusocial insects—those…

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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.