Month: April 2025

A week or so ago, during a Q and A session at a meeting, I was asked by one nature enthusiast why large black bees were bombarding him in his back yard. Without fail, about this time each spring humans who venture too near a child’s wooden play set, wooden benches or railings, mailbox posts, decks, or houses with cedar siding are divebombed by territorial male bees. The bees have nothing against humans. They are simply jealously guarding potential wooden nest sites from interlopers. Interlopers include other male carpenter bees or almost any other creature that comes into range, including humans.  

Wooden structures like this play set bear telltale damage as woodpeckers search for carpenter bees inside the wood. Male carpenter bees zoom around nearby sensing that nubile female bees will soon emerge from these galleries. They divebomb other competing males and nosy humans, aggressively defending their mating territory. When females emerge, they will quickly be mated by diligent guy bees patrolling nearby. Once inseminated, females build new galleries in wooden structures creating nesting sites for their young.

Why do they do this? Here’s the deal. Female carpenter bees build galleries in wooden structures to serve as nurseries for their young. Male carpenter bees go to great lengths to convince potential mates of their worthiness by selecting and defending prime nesting sites. When other male carpenter bees approach defended territories, remarkable aerial battles ensue. Swooping, grappling, and biting often result in both combatants tumbling to earth before one withdraws 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 a nursery for her brood. Her powerful mandibles create a slightly oval to almost perfectly round hole as she penetrates the wood to the depth of 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 removed from one of the benches, 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 multichambered gallery 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. Each 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, pupate, and then after emerging from the pupal case in late summer these new adults push their way past brothers and sisters to escape the gallery and search for nectar and pollen. As summer wanes and autumn waxes, newly minted bees forage during the day and return to their galleries to spend the night. With the end of blossoms in the fall, carpenter bees return to their snug tunnels to chill out until the following spring, protected from the ravages of winter.

In locations where carpenters are present, watching humans duck and cover is almost as entertaining as watching aerial battles among male bees. Male bees lack stingers and although the gals are equipped to sting, I have never been stung by one nor have I heard of anyone who was harmed by these fascinating creatures. Carpenter bees do cause some damage to wooden structures. And once woodpeckers find a structure housing carpenter bees, they get busy and can do some remarkable destruction as they peck holes in the wood searching for carpenter bee babies for dinner. Nonetheless, these entertaining native bees provide important services by pollinating our trees, shrubs, and crops.

At past events such as Maryland Day at the University of Maryland at College Park, which will be held on Saturday, April 26 this year, a thousand or more people visit our Insect Petting Zoo. At the zoo our resident carpenter bees receive much interest and attention. In years past, several children and a few courageous adults held male bees and were fascinating by the buzzing sounds and vibrations generated by flight muscles that power their 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.” I do know, and well said.

Acknowledgements:

Special thanks to Frank Bruno and the folks at the Howard Conservancy who served as the inspiration for this episode. “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.

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In the past month, we explored the questions of how to know where periodical cicadas of Brood XIV might be seen, how to protect your trees from cicada damage and whether or not we should be worried about being bitten or stung by cicadas.  Recently, one of the most frequently asked questions about periodical cicadas is, “when will cicadas appear?” Bug of the Week has been tracking the life history of periodical cicadas for almost two decades, so let’s look at some historical data and see what it reveals.

The “when” question will often be answered with, “when soil temperatures reach 64 degrees Fahrenheit.” This answer comes from brilliant work performed almost 60 years ago by J. E. Heath who discovered that cicadas emerged when “soil temperature at 20-cm depth in seven locations averaged 17.89 C … regardless of date.” This answer holds fairly well even to this day. However, it is not always possible to know just when the magical 64 degrees at 8 inches below ground hits. We explored this in a slightly different way by observing the emergence of straggling Brood X cicadas in the DMV in 2020. In 2020, several locations reported sightings of impressive numbers of Brood X cicadas that appeared one year early. These cicadas are known as “stragglers”. Stragglers are periodical cicadas that emerge years prior to or after the major portion of their brood mates. Often, 17-year cicada stragglers emerge four years prior to the emergence date of rest of the brood. In 2017, Maryland Brood X stragglers appeared on May 14 in Columbia and Gaithersburg. In addition to emerging four years early, sometimes stragglers emerge one year early and this is exactly what happened in 2020. Using data collected in 2020 from the brilliant Cicada Safari App, the very first cicada out of the ground in the DMV was seen on April 19, just south of Towson, Maryland. This one was an extreme outlier. Cicada emergence really picked up in the DMV on May 14, and by May 24, 25% of emerging cicadas were out of the ground. By May 28, 50% of cicadas had emerged, and just few days later, on May 31, 75% of all cicadas had emerged in DC, Maryland, and Northern Virginia. So, if 2025 is anything like 2020, or previous years for that matter, cicadas will be regularly seen as a trickle in some parts of their range in late April or early May with a tsunami hitting in the last two weeks of May and early June as these teenagers are up and out for the Cicadapalooza. Here in the DMV in 2020, the last cicada to emerge was reported in mid-June. Due to a normal life span of two to four weeks, don’t be surprised to see adult cicadas alive and well into the waning weeks of June, but, sadly, in most locations by the 4th of July, their moment in the sun will be all but finished and nothing but a fading memory.

Unfortunately for most of us in the DMV, cicadas are likely to visit only Botetourt, Lee, Russell, Scott, Smyth, Tazewell, and Wise counties in western Virginia this year, with no hope of seeing them in DC and little hope of a visit in western Maryland. But for other states ranging from Georgia to Massachusetts Brood XIV is expected. Of course, the emergence in Georgia will begin weeks ahead of the emergence in Cape Cod. Back in the days of Brood X in 2021, Georgia reported adults in late April but in northern parts of Brood X’s range in northern Illinois, the adult show didn’t get underway until late May according to iNaturalist.     

For seventeen years, nymphs of Brood XIV cicadas have been developing underground. While digging a hole in my yard years ago, I discovered a quartet of periodical cicadas about 14 inches underground. Notice their white eyes and uniformly tan bodies. Here we see a periodical cicada not quite ready to emerge resting at the top of its exit gallery beneath a cinder block. Just behind its red eyes, the dorsal surface of the cicada is uniformly tan. On the evening of its emergence, notice how the dorsal exoskeleton of the fully developed cicada nymph bears two distinct black patches just behind its eyes. I think these are really good clues to help figure out when cicadas are about to emerge in your area.

On a more local level, how can we tell when the big jailbreak is close at hand? The images and video accompanying this episode provide some clues. For weeks prior to emergence, we witnessed almost-ready-to-go periodical cicadas peeking out from their galleries. In these images, notice that just behind the cicada’s brilliant vermillion eyes, the dorsal surface of the cicada’s exoskeleton is uniformly tan in color. On the evening or day of emergence, notice how the exoskeleton of the cicada bears two jet-black patches just behind its eyes. In more than a dozen emergences of periodical cicadas attended by the Bug Guy, this seems to be the clue that cicada emergence is very close at hand or underway. When you see these dark patches, the big show is about to begin. Get ready to enjoy!

Acknowledgements

Three cool articles, “Combining data from citizen scientists and weather stations to define emergence of periodical cicadas, Magicicada Davis spp. (Hemiptera: Cicadidae)” by M. J. Raupp, C. Sargent, N. Harding, and G. Kritsky, “The ecology, behavior, and evolution of periodical cicadas” by K. S. Williams and C. Simon, and “Thermal synchronization of emergence in periodical ‘17-year’ cicadas (Hemiptera, Cicadidae, Magicicada)” by J. E. Heath formed the foundation for this episode.

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