Saturday, July 31, 2010

A Closer Look at Bees: Pollen and Body Parts

The more I learn about bees, the more interesting they become. This morning I was out photographing the insects and flowers in our butterfly garden, and a large portion of the insects I saw were bumblebees, which were mobbing the globe thistles. When the bumbles are this plentiful, it makes studying them a bit easier, for space is at a premium. When they find a good spot to feed and collect pollen, they stay there until the resource is exhausted. So armed with my macro lens, I started stalking the bees.

One busy little lady was well-laden with pollen, her pollen sacs bright orange bulges on her hind legs. This got me to wondering about pollen sacs. What exactly are they? Are they actually pockets in which the bees stuff pollen, or are they just sections of leg around which pollen is piled? I had to know more.

As it turns out, bumble bees have a very interesting system for storing pollen, which begins with pollen collection. Because they are extremely fuzzy animals, pollen sticks to them every time they visit flowers. It sticks to their antennae, their legs, their faces, their bodies. They become one giant pollen magnet.

One of the really neat things I learned about bumble bees (and apparently beetles and ants), is that they actually have a special structure just for cleaning their antennae. Located on their front legs is a special notch. The inside curve of this notch is lined with a fringe of hairs that work like a comb. Have you ever watched a beetle, ant or bee wash itself? It will draw its antennae through this notch, and the comb-like hairs brush off pollen and any other debris that might be there. Pretty nifty.

Meanwhile, the middle legs are also equipped with brush- (or comb-) like hairs. These are run over the body, scraping off the collected pollen. From here the pollen is transferred to the pollen presses located on the hind legs.

At this point we have to take a good look at those back legs. Just like us, the bee’s legs have a tibia, which is the lower leg (think of your calf). On bumble bees the tibia is flat, somewhat convex, shiny and surrounded by hairs, some of which are rather long and stiff. This forms what is called the pollen basket. Located at the lower end of the tibia (think of your ankle) is a comb-like structure, and on the metatarsus (think of your heel or foot) is the press. These two structures work together kind of like levers.

So, the pollen (which has been moistened with nectar to make it sticky) is transferred to the press and the bee manipulates the press and comb to press the pollen onto the bottom part of the flattened tibia. Each new batch of pollen is pressed onto the bottom of the basket, pushing the previous batches further up. When the basket is full, it will bulge with upwards of one million grains of pollen. The hairs that surround the tibia hold the pollen in place while the bee flies from place to place, either collecting more pollen, drinking nectar, or flying back home to stock the nest with this carefully gathered food, which is what her offspring will eat when they hatch.

Bee pollen is considered one of the all-time great foods. Of course, the information I found on the nutritional content of bee pollen is specifically for honey bee pollen, but bumble bee pollen is probably very similar. So, here are some statistics on honey bee pollen:

• It is a complete protein;
• It is the only known food to contain all 22 amino acids that the human body needs but cannot produce for itself;
• It contains more protein than any meat or fish;
• It takes a honey bee about an hour to collect one pellet (basketful) of pollen;
• A teaspoon of honey bee pollen contains about 1200 of these pellets.

(Honey bees, by the way, have crevices on the backs of their knees, and it is into these that the gathered pollen is stuffed.)

It is now clouding up and the bees have probably left the garden. I know, however, that the next sunny day we have, I will be out in the garden watching the bees. I want to see if I can actually witness a pollen press in action. Perhaps some of you will do the same. If you get to see a bee pressing pollen onto its pollen basket, I hope you will let me know.

Ellen Rathbone

Ellen Rathbone is by her own admission a "certified nature nut." She began contributing to the Adirondack Almanack while living in Newcomb, when she was an environmental educator for the Adirondack Park Agency's Visitor Interpretive Centers for nearly ten years.

Ellen graduated from SUNY ESF in 1988 with a BS in forestry and biology and has worked as a naturalist in New York, New Jersey, and Vermont.

In 2010 her work took her to Michigan, where she currently resides and serves as Education Director of the Dahlem Conservancy just outside Jackson, Michigan.

She also writes her own blog about her Michigan adventures.

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