Small Wonders is a monthly column by Field Naturalist Stacia Brezinski that’s rooted in the notion that everything is incredible if we look closely enough.
One of the first things I learned when I started at Maine Audubon last month was that staff will work outside as soon as it’s above forty-five degrees. I might not be quite so hardy, but the other day the temperature hit a sweet sixty, so I plopped myself in the sun outside the Nature Store to answer emails. Of course, I was distracted immediately.
A large bee hovered over a tank of water left out for a field trip. Then, two large bees . . . two large bees who either really didn’t like each other, or really, really liked each other. They faced off, hovering like boxers in a ring, one just slightly higher than the other. They kept about six inches of distance between them, moving together a foot to the right, then a few inches to the left, down almost to the ground, and then suddenly, up! I expected them to stop, but within seconds they’d cleared the roof of our Visitor Center, then the Eastern Red Cedar near the parking lot, then they were high enough that there was nothing nearby that was higher. Eventually, they disappeared into the sky. My guess? They really, really liked each other.
These were Eastern Carpenter Bees. Homeowners may know them as that large bee that looks like a Bumble Bee but isn’t, and makes tunnels in their wood railings. I’m lucky enough to know them in my capacity as a renter, so I was thrilled to see them. Carpenter Bees mate in pairs, and copulation happens in flight. If a female lands, males may grab it and try to lift it back off the ground.
These bees nest in the siding of our administrative building. Males are vigilant defenders of their offspring, dive-bombing or just hovering imposingly in front of a perceived threat. Today it was a nosy Maine Audubon employee. These males, however, lack the ability to sting. Females can, but generally have more important things to do.
Female Carpenter Bees lay their eggs in chambers, or “galleries,” that they excavate with their mandibles. Mandibles are extensions of their exoskeletons, and are made of chitin, a biopolymer that’s proportionally stronger than both bone and steel, and also gives structure to crustaceans and fungi (cook your mushrooms to break down chitin and access the nutrients!). The cellulose in wood is no match, and female Carpenter Bees can chew out an inch of tunnel each day with two approximately two-millimeter-long mandibles until they’re ready to lay their eggs. If an existing nest is used, additional chambers are added so that they can lay more eggs.
A female lays the first egg at the far end of a long chamber on top of a ball of pollen and nectar—food for the future larva. She then constructs a partition made of wood shavings, lays the next egg on its allotment of ‘bee bread,’ makes a partition, and so on until she is finished laying. The last egg to be laid in each tunnel will be the first to mature and emerge, avoiding the classic movie theater, “excuse me . . . pardon me . . . ” situation if they were to emerge in the order in which they were laid. Each new generation of adults leaves the nest in August, forages for nectar, then returns to the tunnels for winter. They’ll mate in the spring, although some females will instead support in brood care, waiting until the following spring to mate.
If you find an Eastern Carpenter Bee away from its telltale round-hole-in-wood, you can distinguish it from similar-looking Bumble Bees by the black bald spot on its hairy yellow thorax and its shiny, black, hairless abdomen. Bumble Bees, in contrast, are hairy all over. Both are important pollinators, which we need desperately to pollinate wild plants and food crops.
Although many homeowners reach for the phone when they discover carpenter bees in their structures, damage is usually cosmetic, and nests rear many generations of pollinators. Of course this is easy for me to say as a renter, but I have to make a case for anything that pulls me away from my computer on a beautiful spring day.
