CARPENTER BEES ARE BORING!

By Arthur V. Evans

It's spring and the eastern carpenter bees, Xylocopa virginica, are back!

The usual suspects of spring are all around me once again, including large, buzzing, blue-black eastern carpenter bees, Xylocopa virginica. They are noisily patrolling dead limbs and wooden structures in our neighborhood as they search for mates and nesting sites. Unlike the social honey bee imported from Europe, carpenter bees are solitary creatures native to North America. The bees buzzing around now reached maturity last summer. Back then they stretched their wings for a bit before tucking themselves away for the winter deep within the recesses in the very nest chamber where they had grown up.

Unlike the dark-faced female, the male Xylocopa virginica has a white "face."

White-faced and stingless, males are very territorial and spend much of their time claiming prominent flowering plants and bare patches of ground as their own. They aggressively drive off other bees and insects and often face-off with unsuspecting humans that unwittingly venture into their territory. The territorial borders of male carpenter bees are quite fluid and change from day-to-day. Amorous males regularly patrol flowers in search of females. Courtship involves lots of loud buzzing and aerial acrobatics, with the pair flying apart and coming together several times.

Dark-faced females are capable of delivering a painful sting, but are relatively docile. They chew their nest tunnels in dead trees, logs, or unfinished wooden structures, especially those with southern or eastern exposures. Females will consider exposed rafters, old house frames, picnic tables, rail fences, posts, trellises, and other exposed wood surfaces as potential nest sites.

With their powerful jaws working non-stop day and night, female carpenter bees will chew a perfectly round entrance hole that is about one half-inch in diameter. After tunneling in about one body-length, the tunnel turns sharply to the left or right at a 90º angle to follow the timber’s grain. They may construct two or more parallel tunnels from the main entrance that measure up to 14 inches long, each slightly wider than the entrance in diameter.

Sometime in May or June, the first egg is laid on a doughy pill of pollen about the thickness of a kidney bean at the end of a blind tunnel. The provision of pollen serves as the sole food source for the developing bee grub. The surrounding wood in the tunnel is then chewed into a fine pulp for form a disk-shaped partition that seals the egg off in its own cell. Each tunnel may have up to 6-8 cells.

Carpenter bees do not eat wood, but rely instead on flowers for nourishment. As the adults forage for pollen and nectar, they will mark each flower that they visit with a repellant chemical, or pheromone, that lasts up to 10 minutes. By skipping marked flowers carpenter bees can save time and effort by avoiding flowers recently depleted of their resources by other carpenter bees.

Tolerance is the key to appreciating carpenter bees. In spite of all the sawdust created by their nesting activities, they seldom cause severe damage. What damage they do cause is easily offset by their pollination services. Our gardens, fields, orchards, and forests would not be nearly as productive if it were not for their efforts and those of other pollinators. Besides, whether they are energetically visiting flowers, zooming through the air in conjugal bliss, or tirelessly engaged in nest-building, carpenter bees are just darned fascinating animals to watch!

© 2010, A.V. Evans

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10 Responses to “CARPENTER BEES ARE BORING!”

  1. Sam Droege Says:

    Art:

    While I haven’t tested this, the females are not supposed to be able to give any kind of significant sting. I know Carpenter Bee biologists who mandhandle many of these bad boys, who have been stung and their observation was that they actually weren’t sure at times if they have been stung or not….

    sam

    Partake as doth the Bee,
    Abstemiously.
    The Rose is an Estate—
    In Sicily.
    – Dickinson

    • Arthur Evans Says:

      Interesting! I had always heard that they were quite capable of delivering a painful sting, but were reluctant to do so!

  2. Art, I always learn something new when I read “What’s Bugging You.” Thank you for that. I’m happy to know that they cannot do serious damage — as I have a few of these guys at home, and always worried about that.
    The more pollinators the merrier, right?!

    • Arthur Evans Says:

      I have to say that “serious damage” is in the eye of the beholder and some home owners have taken me to task on this point!

  3. For several years I’ve allowed carpenter bees to live in the rafters of our south-facing front porch, figuring that the damage caused was less than the enjoyment of watching them. If our porch collapses, I’ll have to re-think that decision.

    Our Ozark carpenter bees just became active a couple of days ago. They always seem to emerge in the spring before there’s an adequate supply of blooms suitable for such a large, short-tongued bee, but they survive so they must know something I don’t. I have watched them doing a lot of nectar robbing on otherwise inaccessible blooms like daffodils and narcissus.

    Great post! Thank you.

  4. We have carpenter bees in our eaves, and the first few years we lived here I’d chase them with hornet spray. I soon saw the futility of that battle, and our house is still standing after 20 years. Now, I just watch them with fascination.

  5. Stephanie Says:

    I’m sorry I’m not as tolerant of carpenter bees. My father has a log home and he has allowed the bees to nest there, unfortunately, the children come back, and their children. He has so many, it’s a major nuisance, perhaps more? I really don’t know how bad the tunneling is.

    Personally, I don’t like all the chemicals and find a badmitton or tennis racket works very well. My husband looks very proud of himself after a successful swat too.

  6. Diana Raymond Says:

    My cousin has a log home as well, and they have been visited by many carpenter bees who have been setting up their nests. She didn’t know what they were at first, she told me they were “drilling holes” in her house. I looked it up and told her what they were – she seems unconcerned, but if I was her, I’d be nervous because I read they can cause structural damage

  7. Nice post! I took a picture of some bees that I think are Eastern Carpenter bees and noticed the nodules on the head. What are those, do you know? I’m not having much luck finding an answer on the web. The pics are on my blog if you want a look.

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