Foraging for pollen.

It is well documented that bees mix pollen in storing it into cells. Cells are not labeled to one type pollen, or by the use of one bee. And it's best they do this for a variety of reasons. But a picture of mixed pollen in cells does not equate into any suggestion that bees mix pollen by collecting from different flowers on the same trip.

Bees cue in on a flower type based on color, form and scent. Once a bee collects from one type flower, rarely does the bees switch to another. It can happen, but as I said, rarely. If it does happen, it is over time that a bee moves onto a new flower source.

If you tell me your reference about bees visiting multiple different flower sources, I will graciously counter with a reference of my own.

I am not sure your references, but von Frisch and E. Opfinger did many studies on the subject. Bees had memories "programmed" to a certain flower scent for at least five days after the source was removed. So the idea or suggestion that bees will move willingly from one type flower to another would be questionable.

Yes, a certain amount of "recruitment" within the hive will sway others to a more nutritious nectar or pollen source. But those changes in plans happen within the hive, not on the fly.

As for your picture, it means little in the conversation. I don't mean that to come across wrong. It's just apples and oranges, that's all.

Hi Bjorn Bee
Great response.

I have read and re-read your post and come to the conclusion that you are not convinced that bees do collect different species of pollen from different flora.

1) Foraging on a Single Plant Species – The Hive & the Honey Bee – Dadent.Quote;
Bees will show a strong tendency to forage repeatedly on flowers of the same species for as long as they are available. However, mixed pollen loads from more than one species are not uncommon. Maurizio (1953) during a three study found an average of 0.9% to 3% mixed loads. Mixed loads where evident throughout the season.

2) Pollen and its Collection – John White.Quote;
It is well to remember that contrary to popular belief, bees do not necessarily adhere to a single species of flower when foraging and a mixture of pollen may be found in a returning bee.

3) Encyclopaedia of Beekeeping – Morse & Hooper.
Quote;
Not all honeybees are always faithful to a single plant flower species. Several studies have been made of pollen loads collected from returning foragers. The data varies, but in general from 1-10% of honey bees have been found with mixed pollen loads, usually from several plant species.

4) Biology of the Honeybee – M Winston.
Quote;
Mixed loads are most commonly found in returning foragers, although multi-species visits have been found in up to 13% (Betts 1935, Maurizio 1953 etc)


That concludes my references and one outstanding feature is it’s only a small percentage of bees that do return with mixed loads, but none the lees it does happen.
I could not find any specific reason for this happening but to my way of thinking it could be due to the fact that a certain species of flower is coming to an end of flowering.
It could also be that it’s a time of change of pollen that is available at any specific time, as we know pollen dehisces from the anthers at different temperatures and at different times of the day.

I have taken pollen loads directly from the legs of bees and have found a mixture of pollen grains.

To finalise, please do not misunderstand what I am saying as I do realise that only a small percentage of foragers will collect a mixed load, but the majority will normally stick to one plant species as long as its producing pollen.

Regards;

I think we pretty much agree that it happens, just at a small rate. I do think that it's probably due to the ending of one bloom period, and the start of another, and I agree with your comments.

The only point that I question is your pollen from several sources in the same pollen basket. Unless you clean the pollen baskets, you would most certainly see a mixture from several trips throughout the day, resulting in "contaminated" data. And those flowers that the pollen is coming from will be visited by more insects than just the single flower source that honey bees normally demonstarte. Pollen crossover from varying insects all visiting that same flower is a real possibility.

Yes, bees in time move from one flower source to another, for reason suggested above. What nobody clearly states is that bees go from dandelion, to apple, to dandelion, and so on.

A certain amount of all foragers are scout bees and first time fliers. These bees no doubt visit all kinds of flowers until a suitable number of flowers, with adequate nectar is found. I could easily conclude that 1% or 5% of bees could easily fall into this catagory. Until a source is found, bees will check out and collect from different flowers. But their desire is to find the most nutritious, and best source. Once found, they will collect from that source.

Bees are told by recruitment that a source is 30 degrees left at 1500 meters. They are not told "A big tree with white flowers, past the barn, and next to the house." They just know that a flower source others are excited about is in a certain direction and at a certain distance. Getting to that tree, they may visit several flowers until they hone in on the location. And what could be expected is mixed pollen. Not by desire but through a plan to find and collect from that one tree they have yet to find.

Some studies in regards to "recruitment" has shown a hive will be recruited and focus all there attention not to just one flower, but to one area. But these same studies can show that different areas can be worked at the same time. You normally see at least several different pollens loads coming in by the same hive. And as you said, flowers like the vine cubits stop by mid-day, and bees may be forced mid-day to change sources. This could also account for different pollen grains being found.

I'm sure when your talking 20,000 foragers, you get many possibilities. But like I said, with few exceptions, bees will work one flower source IF the opportunity exists to continue that collection. They do not go from apple to dandelion to apple and so on in some haphazard random arrangement. Bees are smarter than that and there is no benefit to focus on less nutritious sources as if they want to "blend" their loads. They do that in the hive.

BTW...I love these type discussions. Not to argue, but to learn from. Thank you.