Monday, September 3, 2012

Carpenter Bees Buzzing Pollen

I’ve been keeping watch on the Evening Primrose to find out what insect is responsible for pollination and have finally found a likely candidate.  There have been no late night moth visitors, but I’ve seen a lot of early morning Carpenter Bee activity.

Pollen grains on the body and legs of the bee suggest effective transport of pollen between flowers.  This is what you would expect from a bee.  The unusual aspect is the method in which the Carpenter Bee collects that pollen.

The bee lands on the flower, but it doesn’t stay there.  Immediately after setting down, the bee crawls on over the flower and begins moving down the stem.  The trip across the flower is the maneuver that deposits pollen.

At a point on the stem just below the flower, the bee gets itself carefully positioned.

Then it hugs tightly to the stem and vibrates, an action known as buzz pollination.  The pulsations from the vibrating bee cause the pollen grains to fall from the flower’s anthers.

In some types of flowers the pollen falls onto the bee.  I’m not sure the shape of the primrose bloom allows much of the pollen to fall free of the flower, so buzz pollination wouldn’t appear to be the best strategy for this species.  The fact that the method is working for both bee and flower suggests that I don’t know everything there is to know about pollination methods.  Animals do what they do because it works.  I shouldn’t be second guessing their actions.  


  1. What fascinating images and your explanations. Thanks for sharing.

  2. This is a good story, but I'll offer an alternative. Buzz pollinators typically hang below the anthers of a pendulous flower such as shootingstar or pratridge pea, buzzing to release the pollen down onto their bellies. I believe carpenter bees are essentially brush pollinators (by direct brushing of anthers and stigmas) rather than buzz pollinators, as are their look-alike relatives, the bumble bees.

    The vibration is an ultrasonic boost to the process of biting a hole in the base of deep-tubed flowers, effectively strengthening the bite of the mandible on the lower corolla. Carpenter bees have very short tongues, so they often bite a hole to get at the nectar of flowers with a deep nectar tube, while long-tongued bumble bees rarely do.

    Carpenter bees also use this to significant effect while boring their characteristic burrows in sound wood. Similarly, tropical leaf-cutting ants use ultrasound, produced by their abdominal stridulatory organs, to help their mandibles slice through the tissue, as they cut leaf fragments to carry home for mushroom compost.

  3. Hi James. Yours is a good story too. In fact, it's the one I was thinking of while photographing the bees. The problem began when I went to get photos of the point of nectar extraction and I couldn't find any evidence of their trying to cut through to the nectar supply. I even took some flowers inside and examined the hypanthium through my dissecting scope, but couldn't find any blemish on the tube.

    I've seen Carpenter Bees buzz pollinate tomatoes and nightshades, so I took the story in that direction, even though the flower doesn't seem the right shape for this type of activity.