Tuesday, May 19, 2009

Large Carpenter Bees

Sometimes you miss seeing things clearly that are right under your nose. Such was the case today when I discovered large carpenter bees buzzing about our house. This all started around mid-day when I ventured out to our deck to have lunch. Just then the fox trotted down the driveway with a meadow vole in her mouth. She was oblivious of me (and Bella) as she headed into the woods and back to the den with her meal for the pups.

After she disappeared into the woods, me without the camera, I turned and was face to face (or nose to nose) with a bee. This bee was buzzing about the deck, hovering near me and then Bella, zooming off over the roof only when another bee entered his territory. Only to return to defend his space.

I suddenly realized that this was not a bumble bee and that I had been seeing this bee and its kin buzzing about our house, particularly on warm sunny days and especially near the gable end of our house above the driveway. And I had, quite mistakenly, assumed they were bumble bees.

The reason for my mistake was twofold. On warm, sunny days in spring for several years we have found dead bumble bees on our driveway. Sometimes we had seen Aria catch and kill them, perhaps other times they have just died. So, I had not even considered that the other bees buzzing around the house on hot days were something other than bumble bees, because they looked quite similar. But today I suddenly realized something was different about them.

First, I now noticed, with this bee buzzing about my face, that his abdomen was black and shiny, almost metallic with no hairs. Bumble bees are quite hairy on their abdomen with at least some yellow. And as one who usually prides myself on identifying animals based on their habitat, I kicked myself for just noting that this was not the right habitat for bumble bees. They typically nest in the ground and spend most of their time moving between their nest and nearby flowers. These bees were hovering around the house, far above the ground and from flowers.

So, here is what I found out about my new bee friends, the large carpenter bee, Xylocopa virginica. They appear in spring around April and May, after emerging from their overwintering spots in wood (trees or structures). People first notice the males, which are quite aggressive, although thankfully harmless since they have no stingers, as they hover, like probes. This time of year the bees are looking for mates and good nest sites. The latter being wood that is not painted and is preferably some type of softwood.

Later in the day I was retrieving some things from the laundry line and noticed another bee hovering near the shed to my right. Ah, it's a large carpenter bee I now knew. And then it disappeared. By now, from my reading on the Internet, I knew that females drilled holes in wood to lay their eggs. So, I looked under the shed eaves and found some holes. As I was looking at this one below, fresh wood shavings fell from the hole and I could hear the bee chewing inside.

This perfectly round hole was about 1/2 inch in diameter. The carpenter bee does not eat the wood, just like a carpenter's drill she is making way for something. As she first chews her way into the wood, her path is across the wood grain. About an inch or two inside, she turns at a right angle (apparently always to the right) and continues with the grain, another 4 to 6 inches, and sometimes up to ten feet. Once at the end of her chamber, she places "bee bread" (a mixture of pollen and regurgitated nectar) and lays one egg on top of this "nest." She then seals off this cell with chewed wood pulp and repeats this 6 or 10 times as she backs out of the tunnel.

As I examined the side of the shed, I spotted a splattering of yellow goo. This is the waste from a carpenter bee - a mixture of spent wood shavings and their own excrement. Just below and to the left is another fresh hole. In this hole I could see the 90 degree angle turn to the right.

Once laid, the eggs will hatch in a few days, and the female will die shortly thereafter. The larvae remain in their cells for another 7 weeks or so, when they will emerge as adults. It takes the female 6 days to chew once inch, so getting the full nest gallery prepared will take awhile, so the new adults will not emerge until August. By then the parents will have died.

I suppose lots of carpenter bees could do some damage over time, but for now I will enjoy this "new" addition to our yard (and buildings). The male is harmless, and yes the female will sting, but she is docile and if left alone, is also harmless. As with other bees, the carpenter bee is an important pollinator of flowers and trees. I'll trade a little wood from the shed for this service.

1 comment:

  1. Thank you for this write up! I had some carpenter bees drilling in a rocking chair on my front porch,that I have now designated as 'bee habitat', and I was wondering when the new bees would emerge - 7 weeks. Thank you!

    Susannah, Philadelphia PA