Nature can be incredibly complex and difficult to understand. Every creature is always reacting to the conditions around them, and continually evolving strategies to keep up with an ever-changing world. Because we don’t always understand the full spectrum of challenges facing organisms their behavior sometimes seems illogical. (And, sometimes, it probably is.) Regardless, trying to understand that behavior sure makes ecology fun!
Over the last month, I’ve seen two behaviors that are really interesting but don’t quite make sense to me. Both involve bees.
On several occasions during the last several weeks, I’ve seen bumblebees spread out across the prairie, sitting on prominent high perches. When approached, the bees fly a short distance and then either return to the same perch or land on a nearby one. The second time I saw this, Anne Stine (Hubbard Fellow) and I were out collecting data for a research project. There were dozens of bees on perches, and I just had to know what was going on. Fortunately, I was able to catch Mike Arduser by cell phone and ask him.
A male bumblebee (Bombus griseocollis) sits above the prairie on an unopened stiff goldenrod flower. Platte River Prairies, Nebraska.
I didn’t even finish my description of what we were seeing before Mike was able to tell me the species and gender of the bumblebees, as well as the reason for their perching behavior. He said we were seeing males of the species Bombus griseocollis, and they were on the lookout for new queens making their first foray from of the nests they were raised in. Sure enough, a few minutes later, we saw a gigantic female bumblebee being swarmed by eight or ten smaller males trying to mate with her. Apparently, the perching behavior is successful.
So I guess sitting on perches makes sense. However, wouldn’t it be more effective for the bees to wait right outside the nest exit instead of at apparently random locations across the prairie? Surely these bees – or at least some of them – hatched from the same nest as the queens, so they should know where that nest is. I’d think the males would want to be as close to that exit as possible so they could be the first one to “welcome” the female to the outside world. Maybe there’s a good reason not to do that, but I don’t know what it would be. As I said earlier, this kind of thing is what makes ecology fun!
(Another thing that’s fun is tossing small flower heads or other bumblebee-sized objects near the perched bees and watching them dart out after them…)
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The second bee observation came from the little prairie across town from my house. I was out on a dewy morning, taking a few photographs before heading to the office. It was cool and wet enough that most insects I saw were sitting very still, encased in droplets of water – a very nice situation for a photographer.
Many of those insects had found relatively sheltered and hidden locations in which to spend the night. A few, though, were right out in the open – something that seemed foolish to me, but certainly made it easier to photograph them. One such insect that caught my eye was a medium-sized bee hanging upside down on a grass stem. As I approached it, the bee spread its legs out (defense mechanism?) and by the time I set up my tripod to photograph it, the bee looked like a circus acrobat – hanging upside down and holding on only with its teeth (mandibles).
A female bee (Anthophora walshii) clings upside down to a grass stem with her mandibles. Lincoln Creek Prairie – Aurora, Nebraska.
I don’t even know where to start as I question this behavior. First, why would the bee spend the night out in the open, rather than in a more sheltered location? One explanation, I guess, is that it fears predators that hang out in sheltered locations than those that hunt in the open. More confusing, however, is that this bee is a female ground-nesting bee. She should have nearby a nest tunnel with eggs in it – why doesn’t she stay in that and protect her babies? I asked Mike about this (of course) and he suggested it was possible that she had just become an adult and hadn’t yet had time to build her own nest. I saw two or three other females of the same species nearby – had they also just emerged as new adults from the same nest? I guess it’s possible.
Another view of the same bee.
So, maybe the bee was a young female, still in the process of trying to find a good spot to dig her own nest tunnel. I can buy that, and I wish her good luck if that’s the case. However, that still doesn’t explain why she was hanging upside down by her mandibles… I’m sure there’s a good explanation for that too, but I’m not sure I’ll ever figure it out.
Fortunately, my lack of understanding doesn’t make it less interesting to watch bees – and all the other organisms in the prairie. In fact, quite the opposite is true. If I knew what I was going to see – and why it was happening – there’d be no reason to go to the prairie at all!
Thanks (again) to Mike Arduser for confirming the identifications of these bees and for explaining at least some of their behavior!
The Prairie Ecologist 
I have no idea what species of bee it was, but I also saw the hanging unside down behavior with feet waving outward, and I’m going to hypothesize that it is a defensive behavior. She’s too wet to fly, so she’s just presenting her posterior the better to sting whatever might try to attack her, and at the same time, preparing to clasp onto or push away whatever is a threat with her feet. Best she can do until she dries off. And as far as being at the top of the stem, again – maybe she’s getting closer to the sun and more exposed to the wind to help with that dry-off.
Chris,
If the males from a nest waited near the exit for females from that nest, severe inbreeding would result, think.
Robert and Steve – I think you both are on the right track. Great point about dispersal and inbreeding. I wonder what the reality is. Also, since males aren’t distributed evenly across the prairie, but clustered in certain locations, they must have some idea (guess?) about where the nest is… Very interesting. Good comments – thanks!
Thanks for these fascinating observations, Chris. But why do you say “Surely these bees – or at least some of them – hatched from the same nest as the queens, so they should know where that nest is”? I would expect the males to disperse so as to avoid inbreeding with their sisters.
Wow! I love bumblebee observation posts. I concur with the “male lookout” scenario and want to add that the males are, of course, looking for newly crowned queens. The males emerge first and are essentially freeloaders in the colony since they don’t forage (other than for themselves) and take advantage of of colony resources. But alas, their lives are short and only one is really needed…
As for the bumblebees that “hang out” on flowers overnight – I think that they simply “get stuck” out there after the sun goes down and they can’t orient themselves and/or the evening gets chilly and they “choose” to conserve their resources and camp-out.
Sex, sex, sex: is that all the natural world thinks about?
Pretty much, Brian. When your reason for being is to be good packaging for your DNA, it is important that you have adequate means to transmit it to the next generation.
I have seen bumblebees “overnighting” in the flower heads of my Silphium integrifolium (Rosinweed). Seem too conspicuous, but maybe they just stayed out too late.
I noticed a honeybee sticking straight out of a goldenrod flower, head-first. Upon closer inspection, I saw that a crab spider had him in a death grip around the neck. Watch out!
I enjoyed the posts and comments. I see bumble bees do what I think is sleep on the Joe pye weed. I’m not seeing many there now, since they are finished blooming. I want to find some photos to see if they are actually perched like that.
I enjoy seeing different kinds of bees, wasps and butterflies feeding on the flowers in our yard next to each other without conflict.
Maybe the male bumble bees wait on a high perch so that they can get the best, and not the most available, and possibly related, queen. Just a quess.
Guess, not quess.
Chris, thanks once again for your sharing observations. You remind me just how cosmically ignorant I remain of most that appears right around me in nature, even after 72 years of looking. Our urban deck garden (and the surround wild garden) are filled with several kinds of bees seeking nectar from the various flowers. I’ll start looking closer in the hope of observing bee behavior as it really is, instead of just assuming what they’re doing is all about nectar gathering.
The behavior of the Anthophora bee brings to mind a couple of parasite-induced behavioral changes. One is in snails (Potamopyrgus antipodarum), which when parasitized by trematodes (Microphallus sp.) tend to behave recklessly, climbing to high places where they are more vulnerable to predation by birds (the subsequent host in the trematodes’ life cycle). Another is infection of golden dung flies (Scathophaga stercoraria) by a fungus (Entomophthora sp.), which causes the flies to climb to high places and hang upside-down, the better to disperse fungal spores (once the fungus has finished consuming the fly). It’s probably a long shot, but I wouldn’t necessarily assume that this bee’s behavior is in her own best interest.
David – those are excellent points. I agree that it’s probably a long shot, but I certainly wouldn’t discount it. (It’d make a great blog post if it turned out that the bee’s mind was being controlled by a brainless little critter…)
Hi Chris,
I sent your Goofy Bees post to Dr. Robbin Thorp, and here is his reply that he said I could forward to you.
On Sep 17, 2013, at 4:11 PM, Robbin Thorp wrote:
Gary:
Thanks for the info. Glad to learn that there are people out there who are curious about what they observe and who share their learning experiences with others.
Of course what he saw applies to species with big-eyed males like B. griseocollis. There are other mating strategies among different species of bumble bees including his suggestion they hang around nest entrances. Some species do just that, but if they hang around their natal nest, that would promote inbreeding. Better to find entrances to nests founded by a different queen of the same species. Males of other species patrol and scent mark their routes to attract queens. Darwin made observations on this behavior with the aid of his grandchildren in a garden setting.
Regards, Robbin
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* * * * * * * * * * * * * * *
Robbin Thorp
Professor Emeritus
Department of Entomology
and Nematology
University of California
One Shields Avenue
Davis, CA 95616-8584
Dr. Thorp has generously helped many Bumble Bee Enthusiasts identify their bumble bees including me.
I’m learning a lot from your posts. Thank you for sharing.
Gary
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