College Park Wild: Long live the queens!

By Rick Borchelt

Even though this winter will rank among our warmest on record, for bumble bees it’s still been long and cold. Last fall, the colonies that had grown to hundreds of individuals over the summer collapsed, and the workers died with the first hard freezes — but not before they sent forth a generation of virgin females and male drones.  

The females mated (these fertilized bees are now called gynes); the drones, their purpose in life accomplished, die soon after. Gynes spend the last weeks of autumn hunting for a place to overwinter. A gyne will hole up beneath a pile of leaves, under a log or chunk of bark, or in an abandoned mouse or vole den.  

She’s been sitting out the cold weather ever since. Unlike honey bees, which survive the winter by shivering their wings and bodies to keep the whole colony warm, she’s in a state of deep torpor. While honey bees can venture out anytime the weather warms up a bit during late winter and very early spring to take advantage of the most precocious flowers, a gyne bumble bee has to wait until the weather is warm enough that spring wildflowers are in peak bloom — and she doesn’t risk freezing to death in a cold snap.  

Sufficiently warmed, she’ll clamber out of her winter hibernaculum and find her first meals; pollen and nectar from Virginia bluebells, trout lilies and willows are among her favorites. There’s a special relationship between queen bumble bees and many of our early spring wildflowers, especially Dutchman’s breeches (Dicentra cucullaria). These bizarrely shaped flowers depend almost exclusively on bumble bees to pollinate them; only the large, brawny queens are capable of forcing apart the flower to get at the nectar with their long tongues, fertilizing the plant in the process. 

Spring is when we’ll see gynes, first on flowers, then slowly coursing over the lawn or along the ground in light woods or in a meadow. They’re looking for a fixer-upper. Gynes prefer to use a cavity or hole or tunnel somebody else has already put some work into. Usually, this is on or in the ground — again, often a rodent burrow that comes complete with fur for her nursery.  

Here they gyne will become a queen. She’ll construct a few wax tubes that she packs with pollen and in which she will lay one egg each; the eggs hatch into wriggling, worm-like larvae. For the next few weeks before her nascent subjects emerge as adults, she’ll split her time between foraging for more pollen and nectar, building more wax cells and laying more eggs. Eventually, in May and June in our area, the first female worker bumble bees tumble out of the new hive and begin to contribute to the growing colony.  

The queen now retires into her role of just producing eggs while her youngsters raise more generations of sterile, female bumble bee workers. As the year winds down, the last generation produces fertile females and drones, who begin the cycle again. 

During the summer, bumble bees can be fiercely protective of their nests. Unlike honey bees — for which the act of stinging is fatal in that it rips out their innards along with the stinger left behind in your arm — bumble bees can sting repeatedly. The sting is quite painful, but unless you are stung many times or are allergic to the venom, bumble bee stings are seldom a health risk.  

You might confuse the spring queens as they are out foraging or hunting nest sites with another large, black-and-yellow spring bee — the Eastern carpenter bee (Xylocopus virginica). This is the large bee you see hovering in mid-air around your deck timbers or exposed wood and siding; these are males hanging out waiting for females, which unlike bumble bees are solitary nesters. The female carpenter bee excavates a tunnel in the wood, provisions it with pollen, lays eggs in the pollen and seals the tunnel up until the young hatch the next spring. You can differentiate them from bumble bees because their abdomen is shiny, unlike the hairy abdomens of bumble bees. Like bumble bee drones, carpenter bee males are stingless.  

Maryland has some 15 bumble bee species, all in the genus Bombus. Earning its name, the most abundant is common Eastern bumble bee (Bombus impatiens), followed by brown-belted bumble bee (B. griseocollis) and two-spotted bumble bee (B. bimaculatus). Many of the bumble bee populations in our area are in decline from pesticide use and climate change; several bumble bees that used to live in Maryland have disappeared entirely from the state. One species, the yellow-banded bumble bee (B. terricola), is listed by the state as endangered

Homeowners can do our royal duty for bumble bees by limiting or eliminating pesticide use, including mosquito sprays; ensuring that there are plenty of native spring wildflowers for the queens; and leaving dead branches and drifts of fallen leaves that the gynes can use for winter shelter. 

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Have questions for Rick about the world of nature in and around the city, or suggestions for  future College Park Wild columns? Drop him a note at rborchelt@gmail.com.