Carpenter bees

Carpenter bees often choose yucca flower stalks for depositing eggs and enough nectar to feed subsequent larvae.

As visitors quietly stroll through The Arid Garden, they may be suddenly alarmed by an ear-splitting buzz. It certainly does sound threatening!

Garden volunteers are quick to explain that the sound source, from large black bees, is harmless. Just ignore them, and they will move aside so you can pass. Meet the carpenter bee!

This robust black insect is of the Xylocopa genus, with over 500 species of the carpenter bee found worldwide. Looking much like a bumblebee, they are about one-inch long with a shiny metallic-like body and a booming voice.

Though intimidating by noise and size, carpenter bees are not aggressive. Males guard the nests and are territorial, occasionally dive-bombing and flying erratically around humans. However, it’s all an act because they have no stingers. Females can sting but being docile, they rarely attack unless handled or provoked.

 Carpenter bees build their partitioned nests in burrows of dead wood, bamboo, ocotillo, yucca stems or even structural timbers. As bodies vibrate, their rasping mandibles are working against the wood.

 When constructing a nest the bee will chew one relatively short entrance into wood, then chew another tunnel several inches long at a 90-degree angle to the opening. Here the female will lay eggs starting from the back. There is typically one generation annually.

The mother bee produces some of the largest of all insect eggs. She will then die, but leaves behind enough food in the nest to sustain the larva into adulthood.

These bees return to previously used sites from year to year. It has been reported that they have gone back to the same yucca stalks for over ten years. They do not eat the wood and work near the surface so do little real damage. However, woodpeckers searching for the larvae, may cause extensive damage by enlarging nest holes on unpainted posts, furniture, deck railings, etc.

At The Arid Garden, these important pollinators have been frequently noted this summer in the flowers of Texas Mountain Laurel, Desert Willow, and Mexican Bird-of-Paradise. Their bodies are heavy enough to force open the blossoms for the nectar and pollen to be left in the nest with the eggs.

Not working in swarms or living in hives, these solitary bees are beautiful, humorous, harmless creatures, invaluable for pollinating a part of our desert vegetation. So don’t be intimidated the next time you hear or see the performance of a busy Carpenter bee.


Mary Kidnocker is a University of Arizona Master Gardener who lives in Green Valley. Her articles are featured each Sunday.