Family Ties: Bees’ Murderous Sisters

A Bembix (sand wasp) female, scouting for her nest. (c) MRS 2012 All rights reserved.

It looks like a bee. It flies like a bee. Its home looks like a bee home. If threatened, it will even sting like a bee. But this doting mother, with her fuzzy body and opalescent and black striped abdomen, is a sand wasp (Bembix), and the larvae in her nest, unlike the gentle bee, feed on flesh.

Sand wasps belong to a family of wasps called Crabronidae, which is the closest relative to the bees. In addition to their similar looks and genes, bees and sand wasps share a set of interesting behaviors.

Building a Home

Despite the stereotypical image of at honey bee hive, the vast majority of bees build their nests underground. These nests generally consist of a main tunnel about the diameter of a bee body, with a variety of branching hallways terminating in elaborately constructed cells, the equivalent of a “baby room.” In each cell, she lays one egg and leaves enough food to last the larva until it leaves the nest as an adult. The larva, pictured below in its cell, resembles a maggot or a white worm. Like a caterpiller, it will pupate and undergo metamorphosis into an adult bee.

A bee larva rests on a loaf of “bee bread” (pollen and nectar), on which it will feast until it pupates. Photo taken by Dennis L. Briggs (source: Thorp, R. W. Vernal pool flowers and their specialist bee pollinators.

Sand wasps, just like their sisters the bees, build underground nests for their young. As the name might imply, they prefer to nest in sand (bees tend to prefer finer textured soils). This expecting female is beginning to build a nest for her young.

Bembix excavates her nest

Adult bees and sand wasps both feed on flower nectar, but sand wasp mothers feed their larvae fresh meat. They use their sting to paralyze flies, which quickly become baby wasp fodder. Unlike the mother bee, who gives her larva all the food it will need at once then seals the entrance to her child’s cell forever Bembix mothers continually visit their young with fresh kills. This is why most wasps lack the fuzzy, pollen carrying structures of most bees.

Choosing a Kid-Friendly Neighbohood

While some bees like the honeybee live together in one large nest, most bees prefer to nest alone. This means that a single female builds a nest by herself (where are those pesky males when you need them), and all the larvae in the nest are her own offspring.

Even bees seem to like company, however, as oftentimes these solitary females will choose to build their nests very close to each other. This could either be that suitable sites to build a nest are very scarce, or that there might be some other benefit to living so close together.

Sand wasps also like stay close. The photo above is a picture of a sand pile at a greenhouse. Each of these holes is a separate nest entrance, and in the late Spring/early Summer the sand pile was buzzing with activity.

Now, Where did I put my nest, again?

Bees and wasps both have to make several trips to and from their nest. It is therefore very important that a female be able to remember exactly where her nest is so that she can find it again later. Otherwise her poor offspring will starve and she will have wasted precious time and energy on building a useless structure. Or imagine the embarrassment of mistaking someone else’s nest for your own and entering it only to find the owner already there.

Bees and wasps typically perform a series of “orientation flights” several times a day, in which they scout out familiar landmarks, such as hills, vegetation, or a particular arrangement of stones, so that they know exactly where their nest is.

Next week I’d like to share a special set of photos I took this past summer of a series of bee nests.

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14 responses to “Family Ties: Bees’ Murderous Sisters

  1. Those pictures are amazing!

  2. Thank you for your insightful and witty information, I did not know most bees nest underground!

    • I’m glad you are enjoying the blog. Most bees, such as the bees I study, nest underground. Included in this group are bumble bees, mining bees, and sweat bees. Watch your step 🙂

  3. “It is therefore very important that a female be able to remember exactly where her nest is so that she can find it again later.”
    So what “tools” do bees and wasps use to ensure that they are indeed in their very own nests? Is it by scent, by physical structure…
    Beautiful photos and interesting posts!

    • That’s a very insightful comment. As I will address in a later post, sometimes females who nest close together don’t remember which is their own nest and end up fighting over it. I sometimes wonder if this means that the strongest female, if she is wrong, might end up accidentally abandoning her own young and raising the offspring of her weaker opponent (but this is just speculation from someone who doesn’t know a lot about the subject).

      Every morning, bees do several orientation flights to make sure they can find their way back to the nest. Usually they use visual cues, such as rocks, vegetation, and hills. With the bees in my experiments, I always make sure that I move things around at nighttime when the bees are in their nests so that they don’t get “lost” because a landmark has moved. Bees can also see polarized light, so they can “triangulate” how to get back to the nest, too. It’s all very fascinating, perhaps I shall write a post on the subject sometime soon!

  4. Wow, I really learned a lot. Thanks for this information.

  5. What an interesting way to learn about the different bee worlds. I’m enjoying all the photos, too.

    • Thank you for the compliments! The photos I take are actually the creative impetus for my posts; I look through the photos I’ve taken and think about what concepts they illustrate.

  6. Having lived in a tropical country, the Philippines, the distinguishing factors between wasps and bees are color, size, and structure. But difference in color doesnt seem to be pronounced in Europe, where bees and wasps have almost the same color. It would be therefore interesting to know how both evolved in their niches and if climate change will affect such process of evolution and adaptation to environment. We hardly see wasps in urban areas in the Philippines where weather is predominantly warm, but we see them frequently in the summer in Netherlands. In both areas, bees seem to thrive well.

    On the other hand, climate change will affect habitats – we are witnessing aberrations in seasons compared to the past – summers with heavy rainfall and long winters. Will both bees and wasps survive climate change ? How will it affect habitats and adaptation to environment ? Will color of the animals change as their habitats are destroyed and their adaptation to environment is affected ? Which of the 2 – bees and wasps will more likely survive pollution in urban areas ? Will we see less flowers in urban areas if bees are subjected to severe pollution ? Will wasps become more aggressive as the insect it preys on is affected by climate change ? How will exposure to sulfur nitrates affect them ? Will they migrate to rural areas or simply die ?These are interesting questions.

    • Thank you very much for your intelligent and thoughtful comment! I would love to go to the Philippines someday; the insect diversity there is reputed to be quite incredible.

      I don’t know to what degree I can answer your questions (or to what degree they have been already answered in the scientific literature), but one issue that bees may face in the future has to do with the timing of flowering and the timing of bees emerging as adults going out of sync thanks to climate change. Take the sunflower bees for example; they have evolved to “wake up” when the sunflowers begin to bloom in the summertime. But if the weather changes and sunflowers bloom at a different time than they have in the evolutionary past, will the bees know to “wake up,” or will they come out at the time that the sunflowers would normally bloom and starve to death? Thankfully, at least one recent paper (Bartomeus et al. 2007) seems to suggest that bees and flowers are shifting together, at least for now.

  7. Well it seems bees are more resourceful than I thought. They do have some very sophisticated processes in place!

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