The first week of May is the time to welcome back carpenter bees. While eating a sandwich outdoors at a local bistro, I was amused to see male carpenter bees dive-bombing patrons and pedestrians who dared to approach wooden benches surrounding a patio. You see, male carpenter bees are territorial. They guard resources such as nesting sites used by their mates. Female carpenter bees nest in wooden structures including benches, railings, mailbox posts, decks, and siding. Galleries in wood serve as nurseries for their young. Male carpenter bees appear to go to great lengths to convince potential mates of their worthiness in selecting and defending nesting sites. When other male carpenter bees approached a territory, like a wooden bench in the case of our bistro bees, remarkable bouts of aerial battle ensued. Swooping, grappling, and biting often resulted in both combatants tumbling to earth before one was forced to withdraw from the fray. I watched one victorious male guard a nesting site and soon a lovely and somewhat coquettish lady carpenter bee arrived. She rested on the wooden bench guarded by her suitor and a short but energetic romantic interlude ensued. As far as I could tell, the male flew off somewhere, perhaps for more battles or romantic conquests, but the female bee had different matters to attend. After mating, the she bee begins the task of excavating a hole in the wooden structure to be used as the nest site. The initial tunnel is slightly oval to almost perfectly round and penetrates the wood about a half inch. She then makes a right angle turn and continues tunneling parallel to the grain of the wood excavating a series of brood-cells in a linear tunnel. In a piece of wood from a bench, I observed several tunnels more than a foot in length, some of which branched into secondary galleries. Each tunnel contained as many as thirteen individual brood-cells. To construct each tunnel represents more than a month’s worth of chewing and one has to admire the determination of these industrious gals in excavating a home for their young. After the chambers are built, they are meticulously cleaned and filled with bee bread, a nutritious mixture of pollen, nectar, and secretions from glands on the female’s body. Bee bread serves as the food for the young carpenter bees. Starting at the end farthest from the entrance the female deposits an egg in each brood-cell. The egg hatches into a legless larva that eats bee bread and develops during the course of spring and summer. In brood-cells furthest from the entrance, older larvae complete development first and after emerging from the pupa, these new adults push their way past brothers and sisters to escape the gallery and search for nectar and pollen. In late summer and autumn after foraging all day, they return to their galleries at night. With the end of blossoms in the fall, carpenter bees return to their snug tunnels to chill out, protected from the ravages of winter. Watching humans duck and cover as male carpenters challenged intruders to their territory was almost as entertaining as watching aerial battles among male bees. However, I did calm several patrons by explaining there was no danger of being stung. Male bees lack stingers and although the gals are equipped to sting, I have never been stung myself nor have I heard of anyone being harmed by these fascinating creatures. Carpenter bees do cause some damage to wooden structures; however, these entertaining native insects provide important services in pollinating our trees, shrubs, and crops. This weekend past was Maryland Day at the University of Maryland at College Park. Several hundred people visited our Insect Petting Zoo, and our resident carpenter bees received much interest and attention. Several children and a few cautious adults held the male bees and were fascinating by buzzing sounds and vibrations generated by flight muscles that power the wings. In discussing the antics and activities of carpenter bees, I was heartened to learn that most folks take a “live and let live” approach to dealing with the carpenters. As one lady put it, “This is their world too, you know.”

Special thanks to John Davidson for sharing good carpenter bee stories with me. “Bionomics of large carpenter bees of the genus Xylocopa” by Gerling, Velthuis, and Hefetz” was used as a reference for this Bug of the Week. To learn more about carpenter bees, please visit these previous episodes on Bug of the Week: Carpenter Bees - Xylocopa virginica and Busy carpenters, lazy carpenters - Carpenter bees, Xylocopa virginica, and the following web sites.

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