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Just a fleeting hypothetical that crossed my mind. Say that no flowering plants exist. I don't know why - say a world has been terraformed with various Earth species. Bumblebees are present, but flowering plants are not. The question is -

Would Bumblebees be capable of adapting to a world without flowers, or would they become extinct from overspecialisation?

Any answers would be greatly appreciated.

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    $\begingroup$ Are they carried on that world by somebody else, or would they exist there for a long time? $\endgroup$ – L.Dutch - Reinstate Monica Sep 30 '18 at 16:54
  • $\begingroup$ Vote To Close - Primarily Opinion Based, since bumblebees would not exist without flowers. $\endgroup$ – RonJohn Sep 30 '18 at 16:59
  • $\begingroup$ @RonJohn I don't think that's strictly true, they could exist. I'm working on an answer right now. $\endgroup$ – John Locke Sep 30 '18 at 17:03
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    $\begingroup$ @RonJohn Just posted an answer. Although even if bumblebees could not exist without flowers, that wouldn't make the question too opinion based. A simple no with an explanation of their food requirements would be a suitable answer, and there are only a few other possible answers. $\endgroup$ – John Locke Sep 30 '18 at 18:34
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    $\begingroup$ @RonJohn "Vote To Close - Primarily Opinion Based, since bumblebees would not exist without flowers." So you say you're voting to close, yet you also say that the reason why you vote to close does not apply? "Primarily opinion-based" means answers will be based on opinion, not fact, yet you state that a fact-based answer ("bumblebees would not exist", "bumblebees need nectar") is possible. You can downvote for lack of research, or vote to close as not about worldbuilding, but since you clearly say there's relevant facts to base answers on, I don't see how you can say that this is POB. $\endgroup$ – a CVn Sep 30 '18 at 19:58
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Bumblebees eat nectar and pollen. Source

Gymosperms

Gymnosperms are plants that have small flowers. The flowers have no special coloration or smell. If you don't count them as flowering plants (they technically have flowers, but not what we think of as flowers), gymnosperms will still be around. The flowers release large amounts of pollen into the air in the hopes that some of it will land on the flower of a plant of the same species. If these plants still exist, bumblebees would collect pollen from them as a food source. The bumblebees would collect pollen from the plants and off of any surfaces where the pollen would have landed. With this behavior, I think bumblebees would still be able to survive. Without flowering plants, gymnosperms would have less competition and wold increase in number.

Conifers

In a world without flowering plants, you will still have conifers. Conifers don't have flowers. Like gymnosperms, their pollen is also blown by the wind and ends up in large amounts on the ground. The bumblebees can eat the pollen on the trees and anywhere pollen has collected. While conifers are not as common as gymnosperms or angiosperms [citation needed], they would provide a good food source for bumblebees. While the bumblebees would decline in numbers, they could still survive the loss of angiosperms and gymnosperms.

but they need nectar. IOW, pollen without nectar means no bumblebees.

Thanks to @RonJohn for pointing out that they would need nectar (emphasis theirs). I looked it up and found this article, which says that nectar is a carbohydrate. It doesn't seem to have any essential proteins or fats like pollen does (essentially empty calories), so I would guess that with a little adaptation, the bumblebees could survive without any nectar. That said, if angiosperms all die out at once, that will probably kill off all the bumblebees.

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  • $\begingroup$ Gymnosperms are not flowering plants. (Flowering plants are called "angiosperms".) Gymnosperms truly really do not have flowers, nor do they have any kind of flower-like structure. Conifers are gymnosperms. Their cones are not homologous with the flowers of flowering plants; they are more in the nature of short shoots carrying modified leaves and branchlets. $\endgroup$ – AlexP Sep 30 '18 at 18:39
  • $\begingroup$ @AlexP This link describes gymnosperms as not having flowers, and being wind-polinated, and then goes on to explain their structure of wind-pollinated flowers. Am I confusing wind-pollinated with gymnosperms? $\endgroup$ – John Locke Sep 30 '18 at 18:42
  • $\begingroup$ "which says that pollen is a carbohydrate". Did you make a typo? I think that should be "pollen is a carbohydrate". $\endgroup$ – RonJohn Sep 30 '18 at 18:44
  • $\begingroup$ @RonJohn Yes, thank you. I will edit that out. $\endgroup$ – John Locke Sep 30 '18 at 18:46
  • $\begingroup$ Pollen is not not not a "carbohydrate". In fact, pollen is not a chemical substance. Pollen is the collective name for the "male" spores produced by the "male" parts of a sporophyte, which, when and if they fall on a receptive pistil will grow into a (greatly reduced) male gametophyte. (And in the link you provided, the phrase "any flowers produced are not scented" refers to the flowers of anemophyle angiosperms.) $\endgroup$ – AlexP Sep 30 '18 at 18:48
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Maybe.

bee feeds on honeydew https://bugguide.net/node/view/726266

Bees drink nectar. But under some circumstances (like lack of flowers), bees can feed on the excretions of plant parasites like aphids and scale insects. That is what this honeybee is doing.

https://www.theguardian.com/environment/2017/jun/09/sticky-solution-aphids-honeydew-suits-bees-country-diary

...I went outside to investigate, and discovered that the bees were landing on the foliage and unrolling their tongues to mop up honeydew, the sticky fluid excreted by aphids as they feed.

Surprised by this behaviour, I contacted the Bumblebee Conservation Trust. They told me that there is limited research on the subject, but that every year they receive reports from members of the public who witness this phenomenon.

It is most often observed in areas where there is little in flower, which could indicate that honeydew is a nectar substitute when suitable forage plants are scarce.

The "honeydew" excreted by these plant sucking insects is of great interest to ants, who are well known to farm and protect herds of aphids and the like to preserve a supply of honeydew for themselves. Like ants, bees will eat dropped sweets and honey and so it makes sense that they too would like sweet honeydew.

Aphids can make honeydew from nonflowering plants. Junipers are gymnosperms and don't make nectar. But aphids like them.

https://homeguides.sfgate.com/bees-flies-juniper-bush-93768.html

Don't avoid planting juniper (Juniperus spp.) because you noticed bees or flies on a neighbor's tree or shrub. The annoying insects aren't attracted to the evergreen itself, but to the sticky sweet honeydew excreted by even smaller pests that feed commonly on junipers.

A world without flowers might also be largely without the predators that control aphids and scale insects. If these insects are widespread, they could make bee food adequate to sustain bumblebees.

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  • $\begingroup$ This could lead to the evolution of farming bees! $\endgroup$ – Joe Bloggs Oct 1 '18 at 9:57
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Sure

According to this article bees are perfectly happy feasting on things-that-aren't-flowers. Like insects.

Wild bees may be responding to climate change and urban expansion by relying on insects to get the sweet stuff, according to a study

The first thing to remember about bees is that there are dozens of species of bee.

There are nearly 20,000 known species of bees in seven recognized biological families.

So we've got a few varieties to play with. Back to that article:

Climate change has caused some flower species to bloom at different times than they have in the past, Meiners said. This causes a potential mismatch in bees and flowers meeting at the right time. With urban development also reducing the number of wildflower habitats, wild bees could come out of the ground to find very little food available to them.

When this happens, Meiners discovered that some wild bees turn to plant-feeding insects for food. The plant-feeding insects suck out nutrients from their host plant, and then secrete a nutrient-rich carbohydrate known as honeydew that is similar to nectar sugar, Meiners said. “We are the first to study solitary bees feeding on honeydew while they wait for more flowers to bloom,” she said. “And one of the most interesting things about this behavior is that these bees can find the honeydew without any colorful petals or scents to guide them there.”

Now, the lack of all angiosperms might play havoc on the bee populations for years, they'll still probably survive as a whole, but expect more solitary bee species and fewer colonies.

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    $\begingroup$ People just don't realise how many species of bees and wasps are not social. For ants or termites sociality is a given, but for bees and wasps it's actually the exception, not the rule. $\endgroup$ – Joe Bloggs Oct 1 '18 at 5:57

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