Flowerland Friend: The Bumblebee Hum

One of my first memories as a small child was watching a bumblebee (or bumble bee) on a flower in front of our house. He was fumbling about in a clumsy manner and then started to “fall”. Quickly, I put my fingers out to catch him….and then… the pain. I was only two, but I forgave him quickly with the help of my mother. She calmly explained that the bee didn’t mean to hurt me, and that he needed to get back to work. This two-year-old explanation still applies today to how we should treat bumblebees.

Bumble bees are not normally aggressive unless prevoked. They are much less aggressive than the honey bee. Care should be taken not to disturb nests. Nests can be found in trees, abandoned debris and underground.
Bumble bees are not normally aggressive unless provoked. They are much less aggressive than the honey bee. Care should be taken not to disturb nests. Nests can be found in trees, abandoned debris and underground.

Bumblebees are important pollinators for native food plants, such as potatoes, blueberries, cranberries, eggplants, and raspberries, and for important crop plants such as red clover, alfalfa, and cotton. Further, bumblebees are the only insect capable of pollinating the Solanaceae family (see blog post “Don’t Eat these Greens!”), a plant family that contains important crops such as tomatoes, peppers and tobacco. Approximately 8% of the world’s described 250,000 species of flowering plants, the angiosperms, rely exclusively on bumble bees for pollination.

Bumblebees are a ground-nesting bee, although they can also nest in other protected areas such as stumps and debris. Their nest holes are usually less than the size of a quarter and have a short trail leading into the hole (a landing strip of sorts). The nest usually consists of about 200 bees per colony, with only the Queen surviving the winter.  In early May, the Queen emerges to start her colony. She begins this process with a mass collection of pollen that she moistens with nectar called “Bee Bread” or Ambrosia (meaning the food of the Greek gods) that she will use to raise the first generation of workers.

Bee pollen that has nectar added for food is also known as "Bee Bread". It contains special fungi and bacteria for larvae development.
Bee pollen that has nectar added for food is also known as "Bee Bread". It contains special fungi and bacteria for larvae development.

Nectar is stored in wax “pots” and pollen is stored in the wax “cells” with the larvae which they will feed on themselves.  Because bumblebees are incapable of feeding each other directly, so they must use indirect transfer methods such as storage.

Bumble bees store nectar, pollen nearby larvae for feeding. The nectar is in wax capsules that larvae can feed on by chewing through cell walls.
Bumble bees store nectar, pollen nearby larvae for feeding. The nectar is in wax capsules that larvae can feed on by chewing through cell walls.

After the initial brood of about 20 bees, the colony begins to establish with reproducing males and females that mate during flight (if you have ever seen two bees that appear to be fighting in the sky, that is actually what is happening).  Reproduction, aside from the Queen, is unusual for bees because usually workers are sterile. The young produced from the male and female  workers will only be male.

The bees continue the process of collecting pollen to feed their young:

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Can you hear the buzz? Bumblebees are capable of what is known as “Buzz-Pollination” or “sonication”.  A buzz caused by rapid contractions of their flight muscles causes vibrations to roar through the flower at about 400 hertz (Hz). This means that tightly held pollen is vibrated loose from plants, allowing it to be captured for use, and set free to cross-pollinate crops. The pollen is captured on the bee in its tiny hairs and in “pollen baskets” on their hind legs that can be seen in the video above.

Bumblebee with a load of pollen known as a "pollen sac".
Bumblebee with a load of pollen known as a "pollen sac".

Through the season new Queens are born. Depending on the species of bee, there can be up to 30 queens born per nest. Males born from workers and the queens are driven out of the nest. They will continue to feed and pollinate, and eventually mate. The males will die in the fall and the queens will over-winter until the process begins over again in the spring.

The large queen bee, the female worker, and male drone. Only the queen and workers can sting.
The large queen bee, the female worker, and male drone. Only the queen and workers can sting.

Unfortunately, Bumblebees are on the decline. Over-use of pesticides, disease,  habitat loss and over-all misunderstanding of the bees have resulted in a loss of many species. Others are threatened or endangered. This has resulted in a subsequent decline in the species of plants that they pollinate. Through understanding and respect we can do our part in saving this very important part of our ecosystem and garden.

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