Wild Side: She’s a polyester bee

But there’s nothing inorganic about her.


How does a female solitary bee start her day? I’d never asked myself the question, but recently ended up with a chance to answer it anyway.

On a long drive back to the Vineyard on April 24, I stopped off at a familiar site in Lexington to break up the trip with a little late morning naturalizing. It was a chilly day, and the ground and vegetation were still wet from overnight rain. But the clouds were breaking, and I was confident that the appearance of the sun would quickly stimulate some insect activity. I parked the car and hiked a half-mile or so to a site that consistently has a nesting aggregation of one of my favorite bees, Colletes inaequalis.

I arrived to find, as I expected, a concentration of several dozen nest burrows spread over perhaps 400 square feet of mostly bare soil. Each hole was about the diameter of a pencil, surrounded by a mound of loose soil produced as each bee excavated her burrow. There was no activity at first, but as the sun strengthened, I noted a few male bees patrolling in hope of a mating opportunity. A few minutes later, the first females showed their faces at the mouths of their burrows.

I watched one female closely as she lingered at the opening, soaking up the sun, and perhaps scanning the area for hazards. Female solitary bees have good reason for caution: The bee world is rife with so-called “cuckoo bees,” parasitic species that lay their eggs in the nests of other bees, usually with fatal results for the offspring of the host. The life of a female solitary bee is dominated by competing impulses: to forage for pollen with which to provision her nest, or to remain in her burrow, ready to block the entry of nest parasites.

After about 10 minutes, my little friend concluded that the coast was clear, and walked tentatively out of her burrow. She spent a few minutes grooming — as she emerged, she carried small clods of dirt from her night spent underground — and then she gave her wing muscles a brief warm-up, first flexing her wings to and fro, then engaging in a few bursts of stationary flapping. Preflight checks concluded, she took to the air, flying slowly at first in tight circles around her nest, then picking up speed as the circles widened.

The gyres eventually expanded to a diameter beyond where I could follow her flight, and she was presumably off to find flowers. I imagine this flight pattern of expanding circles is a way to memorize the location of her nest, which she’ll need to relocate after traveling however far she must to find a source of pollen.

Colletes inaequalis is a member of Colletidae, a family sometimes called “polyester bees” because females line their nest burrows with a plastic-like substance (perhaps to help regulate humidity inside the nest). The species is not often reported on Martha’s Vineyard: A major bee study in 2010–11 recorded only one individual, and the iNaturalist platform only has a handful of Vineyard records for the species.

They may be overlooked, though, given their foraging habits. As a bee of the very early part of the season (late March into May in our region), they’ve evolved to forage largely on flowering trees — in my experience, mainly willows and red maple. Much of their foraging takes place out of sight, well off the ground. Overall, I’ve done better finding this bee by looking for nests rather than searching for foraging individuals. On the mainland, the C. inaequalis seems more common, and is one of the most frequently reported early-season bees.

Despite its fondness for flowering trees, this species has wide tastes, and is known to forage on plants in at least 17 plant families. Indeed, versatility is this bee’s middle name. Colletes inaequalis occupies much of North America, from Georgia north to Nova Scotia, from the Atlantic Ocean west to the Rockies. As far as I can tell, the species prefers to nest in open areas with dry sand; but I’ve also seen nests in settings as diverse as lawns and white pine woodland. It would be interesting to know if nests are equally successful across that vast geographical area and that wide range of habitats.

Females run about a half-inch long, and males are a bit smaller, which actually makes this species fairly large for a solitary bee. With a fuzzy thorax and bands of hair along the rims of the abdominal segments, Colletes inaequalis shows few obvious features that distinguish it from the host of other bee species with similar life histories. Details of the facial structure and the shape of certain wing veins are helpful for recognizing this species, and indeed the genus Colletes in general; regrettably, these are of little use to the casual observer.

I hope the members of the Vineyard’s modest population are having a successful spring. They’re wonderful bees.