Pollen collection by honey bees

While we normally think of honey bees collecting nectar, an average-size colony may bring in 100 pounds of pollen in a season. Pollen is an essential part of the honey bee diet, providing a wide range of nutrients including protein, carbohydrates, lipids, vitamins, and minerals.

Although a tough outer coating protects the pollen from environmental stressors, honey bees have enzymes in their digestive tract that split the grains apart at a weak point. The interior is then digested and the empty husks are excreted. Most of the pollen is eaten by nurse bees. They use the nutrition absorbed from it to secrete royal jelly from their hypopharyngeal glands. The jelly is fed to young larvae, including workers, drones and queens. After about three days the jelly is mixed with bee bread—a mixture of whole pollen, honey, and enzymes—and fed to the workers and drones until they spin their cocoons. The queens receive a steady diet of royal jelly throughout their development.

Most bees collect just pollen or just nectar on any trip, but a few carry both at the same time. The pollen is stuffed into hairy receptacles on their hind legs called corbiculae. A single bee can carry about half her own body weight in pollen.

Once back at the hive, the workers stuff the pollen into an awaiting cell. Unlike nectar-carrying bees, pollen-carrying bees have to off-load it themselves. In addition to depositing the pellets from their sacks, they may also groom away any pollen that is stuck to their bodies. The pollen is stored in cells at the perimeter of the brood nest, forming a ring around it. During the brood rearing season, the pollen is stored for only a few days. During the winter it is stored for much longer.

Honey bees usually forage on only one kind of flower on any single trip. This is nature’s way of assuring that plants are cross-pollinated. So a bee going to blackberries, keeps going to blackberries until there are no more blackberry flowers, then she will switch to something else. Honey bees collect pollen even from plants that don’t provide nectar, such as corn. In corn-growing regions, pesticide-contaminated corn pollen is suspected of causing severe health problems within the hive.

Rusty

Comments

Cody Freeman
Reply

hi Rusty, this is Liesl’s husband. she told me about your bee blog and i decided to check it out…Very cool! I think i have learned more about bees in the last 10 minutes than in my entire life so far. Liesl and I have been talking about maybe starting up a bee hive in the future, so i am sure when that time comes we will want your expertise. I was a little confused about something in the Pollen collection article. You said that “bees forage on only one kind of flower on a single trip. This is nature’s way of assuring plants are cross-pollinated.” is that correct? to me it would make sense that if they only gathered pollen from ONE flower type that they would NOT be cross-pollinating.
Anyway, I look forward to reading more about these bees and i am going to start right now.

thanks
Cody

Rusty
Reply

Hey Cody,

Thanks so much for your comments. I would love to help you and Liesl set up a colony of bees anytime you’re ready.

This is really silly, but I just wrote a long answer to your question and it disappeared. Drats! I can’t figure out where it went, so I’ll just have to start again.

I think the term “cross pollination” is the thing that is confusing you. The “cross” part refers to pollination between flowers of the same species, instead of pollination within an individual.

If you shook one flower, and the pollen dropped from the anther (male part) onto the stigma (female part) that would be self pollination. It usually doesn’t produce seed or a fruit.

Cross pollination happens when the pollen from one flower is transferred to the stigma of a totally different flower on a separate plant. The flower has to be of the same species, but it’s a different individual. So, for example, when pumpkin pollen lands on a different pumpkin flower, it will fertilize and make a seed, but if the pumpkin pollen lands in the flower where it came from or on a kiwi flower, for example, nothing happens.

So if a bee went from a maple, to a cherry, to a dandelion, to a mint, to a cucumber, nothing would ever get pollinated because they are all different species (just like a dog can’t “pollinate” a cat.) But if the bee goes from one pumpkin plant, to another pumpkin plant, to another, you will get pumpkins on all of them. Very cool. Anyway, that is what is meant by cross pollination.

If you’re still confused, I’ll try again.

Rusty

Joanna
Reply

Hi again- this entry came up on some of the results in my Googling. I’m finding a LOT of different numbers and if it is annoying to have me all over your site with this then please tell me to stop! Here http://edis.ifas.ufl.edu/in868 says a bee can carry roughly 1/3 (35%) of its body weight in pollen. Here http://www.beeccdcap.uga.edu/documents/CAPArticle10.html says the average weight of a honeybee is 120mg and that they can collect 7.6- 8.6 mg pollen. There were several other less scholarly articles with numbers all over the place- “HBs can carry 2g in their corbiculae”, “20 mg of an average weight of 80 mg”. I can’t paste in cites as those were pdfs. There was also a really old article (June 1964 Soc. for Study of Evolution) Kerr and Herling indicating that bee weights range from a low of 81.2mg to a high of 110.4mg. The numbers are similarly all over the place for nectar load/weight but nearly universally indicate that bees can carry much more nectar than pollen- and I’m guessing that’s primarily due to load placement. In any event, I think it’s conservative to conclude that if there is 60mg of a single varietal of pollen than meets the minimum for an average HB- understanding that the average HB will pack at its own discretion. A 2005 article in the J of Apicultural Science indicates a pollen weight of 9.5mg per 10 flowers of a specific rhody (or .95/single average flower). So, for rhodys it would be roughly two good shrubs with 70 or so flowers. Again, apologies for the quasi irrelevance, its just helpful to me to try to think of the two things together- plantings and bees and how many flowers is enough pollenwise/nectarwise. I’m going to go obsess over something else for a moment and leave you be!

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