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Why do honey bees need fur?

Fur. I think of it as hair, but fair enough. The fur on a bee is vital to its survival. Virtually all bees have branched hairs somewhere on their bodies. In fact, the presence of those branched hairs is one of the major ways bees can be distinguished from other insects.

Bees are vegetarians. They collect nectar from flowers for their energy needs, but they also collect pollen which supplies them—and their young—with protein, lipids, and nutrients. As a bees goes from flower to flower, pollen grains get caught in the branched hairs, which facilitates their collection by the bees. Bees carry pollen in different ways, but a honey bee uses her hairy front and middle legs like brushes to comb the pollen off her body and pack it into hairy recesses on her rear legs. These hairy recesses are called pollen baskets or corbiculae.

Thanks to hairy . . . or furry . . . bodies, the bees inadvertently leave some of the pollen grains behind each time they visit another flower, which is the primary mechanism of insect pollination. Without those furry bodies flitting from flower to flower, life on earth would be very different indeed.

Buttercup bees: they are what they eat

No, no. I meant they wear what they eat. Imagine going to the store for peanut butter and coming home slathered in the stuff. That’s what bees like to do.

Pollination is enhanced by the pollen that sticks to the hairs of the bee’s body. This pollen adheres easily, and when the bee brushes against the stigma of another flower, the pollen is just as easily released–all of which insures pollination will occur. On the other hand, the pollen stuffed into the honey bee’s corbiculae forms a hard pellet. Pollen stuck together in these tight packages is essentially unavailable for pollination.

Flowers compensate for this loss–and other natural losses–by producing huge amounts of pollen. It is not unusual to see pollen coating the surfaces of cars, ponds, pools, and lawn chairs. Sometimes clouds of it waft from trees and shrubs when the wind blows. The amount the bees pack out to the hive is trivial compared to the amount produced.

If a bee comes back to the hive covered in pollen, she stuffs the pellets into the comb and other bees assist her in grooming away the rest. This bonus pollen is mixed with nectar and stored in cells just like the pellets. Nothing goes to waste.

Rusty

Honey bee after visiting buttercups.
Another pollinator enjoys the buttercups.
Buttercups (supposed to be lawn)

Honey bees collect Alaska cedar pollen

Yesterday, when I saw hundreds of honey bees in the Alaska cedar hedge (Chamaecyparis nootkatensis) in front of my house, I thought they must be collecting propolis. But on closer inspection, it was obvious they were collecting pollen. Their corbiculae were full of pollen the exact color of the pollen-bearing strobili that adorned the tips of the branches of some of more mature trees. When I pulled the branches apart for a closer look, clouds of brownish pollen floated on the air.

A little research revealed that many kinds of evergreen tree pollen are collected by honey bees. Although it is not considered high-quality pollen as far as bee nutrition is concerned, if there is little else available, the bees will eagerly gather it.

When the sun finally came out–later in the afternoon–the honey bees abandoned the cedars in favor of something else. In the photo below you can see the full corbiculae of a cedar-foraging honey bee.

 

The pollen baskets are barely visible, camouflaged against the pollen-bearing strobili.
The pollen baskets are barely visible, camouflaged against the pollen-bearing strobili.

What is pollenkitt?

Pollenkitt is a sticky covering found on the surface of pollen grains. It is also spelled “pollen kit” or “pollenkit” and is sometimes called “pollen coat.” It is found in some plant families more often than others, but it is especially common in plants that are pollinated by insects. Because of this, scientists believe that one of the major functions of pollenkitt is to help the pollen stick to the bugs.

Honey bees have special body parts where they pack pollen to be carried back to the hive. The parts—one on each hind leg—are called corbiculae or “pollen baskets.” The corbiculae are covered with hairs which help to hold the pollen in place, but very sticky pollen can form large clumps—something that makes provisioning even easier.

The pollen from many wind pollinated plants, such as grass, is much drier and not nearly so sticky. This pollen has to be carried in smaller clumps and so the bees have to make more trips to collect an equal amount, which wastes both time and energy.

It is interesting to note that the pollen in the corbiculae is not the pollen that is transferred to other flowers. The pollen that does that job is the pollen that sticks to the body of the bee and rubs off when she visits the next flower. But pollenkitt facilitates this transfer as well: the pollen sticks to the bee until she rubs up against another flower, and then the pollen sticks there instead.

Plants that are insect pollinated not only have sticky pollen, they have lots of pollen. This provides the win-win relationship that defines plant-pollinator mutualisms. In this case, the plant has to expend lots of energy to produce excess pollen with sticky coatings to attract the bees. In turn the plant gets pollinated. The bees benefit from lots of pollen that is easy to carry home. In addition, pollenkitt contains lipids, proteins, and phenolic compounds which are important to honey bee health.

Researchers have suggested many other reasons for pollenkitt and, in truth, it probably has multiple functions. It may keep the pollen from blowing away or drying out, or it may protect the pollen from ultra-violet radiation and certain pathogens.

Rusty

Pollen collection by honey bees

While we normally think of honey bees collecting nectar, an average-size hive 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