Most homeowners in North America are familiar with Carpenter Bees. In the eastern US, where I live, Xylocopa virginica, the Eastern Carpenter Bee is often mistaken for a Bumble Bee that has a naughty habit –from the human perspective– of drilling (or chewing, to be accurate) its way into wood. It goes without saying that this isn’t the most popular species of insect. However, despite their choice of inconvenient nesting sites, Carpenter Bees in the genus Xylocopa are in fact important pollinators.
What I didn’t realize until just recently is that there is another group called ‘Small Carpenter Bees’ in the genus Ceratina that look nothing like their larger cousins. And, even better, they nest in hollow twigs and stems rather than in holes in lumber. While it can be difficult to determine the exact species of Ceratina that you’re observing in the field, Small Carpenter Bees have a few general characteristics that make it easy to identify them to genus level. Typically, in North America, Ceratina species are a dark, dull metallic blue without very much hair. In this regard, they are slightly wasp-like. Sam Droege wonderfully describes them as having an abdomen that is “ribbed like a plastic water bottle.” This is a great way to describe a feature that is fairly unique to members of this genus.
It’s easy to encourage Small Carpenter Bees in your garden, and you should, since they are also great pollinators! One of the best things that you can do is simply allow some pithy stalks to remain in your garden overwinter. Sunflowers, mints, and Joe-Pye Weed make great shelters for Ceratina. Although this is a solitary species (like the majority of North American bee species) groups will often gather in small aggregations within plant stalks. Encouraging native bees in your garden is very easy! They simply need shelter, a food source, and homeowner who goes easy on the pesticides.