Spring arrives and with it, delightful Plasterer bees: Colletes spp.

 

From the safety of its burrow, a plasterer bee takes a peek at a bug geek with a camera. How cute is that?

 

We visited plasterer bees in the spring of 2020 at the onset of the Covid epidemic. Let’s go back in time to that earlier episode and see how these spring beauties roll.   

Soil conditions in this lawn support nesting sites for thousands of plasterer bees. Credit: Marlene Stamm

April 13, 2020 - “Fortunately, before the shelter-at-home orders kicked into high gear, I was able to visit a park and vacant golf course to piece together more details about these fascinating ground-dwelling bees known as plasterer bees. Along with beetles, flies, and butterflies, bees are among the premier pollinators on the planet. Plasterer bees are some of the very first native pollinators to appear each spring. The name plasterer stems from their intriguing behavior of building galleries in the ground and then coating the interior surface of their burrow with a thin, glossy, translucent material produced by a gland in their abdomen. Plasterer bees use their tiny mouthparts to remove the soil when constructing their galleries. The excavation is accompanied by a buzzing sound that may help loosen particles of soil and aid in the digging process. The bee’s mouthparts are also used like a mason’s trowel to spread the glandular secretion on the inside of the burrow before it dries into a cellophane-like coating. How clever! This habit of sealing their galleries gives this bee the common name plasterer bee.

What’s up with all these holes in the ground? Watch, listen, and learn a little bit about the fascinating lives of plasterer bees.

Plasterer bees are relatives of honey bees and bumble bees but, unlike their cousins, these bees are solitary. Rather than living in a communal nest, each female plasterer bee constructs a subterranean gallery of her own to serve as a home for her brood. Burrows are provisioned with a semi-liquid concoction of nectar and pollen from flowering plants that bloom early in the spring. This yummy delight is food for bee larvae that develop during the summer and fall within the galleries. Although they are not considered social insects, large numbers of plasterer bee galleries are often abundant in close proximity in sandy soils with thin vegetation.”  

Thin grass, a sunny hillside, and sandy soil provide nice conditions for plasterer bees in my backyard.

While exploring nesting sites along Disc Golf Course in Patapsco State Park last week, I was delighted to see dozens of small plasterer bees zooming inches above the ground. While swarming bees at the margin of fairways might dismay some disc golfers, bee dread is unwarranted. Unlike yellow jackets, baldfaced hornets, and other stinging terrors, plasterer bees are docile and extremely reluctant to sting. Remember, each female bee is a mother and to risk her life by stinging a human could mean instant curtailment of her reproductive potential should she die in the encounter. Over large areas of a balding zone in the rough, several burrows could be found in each square meter of ground. The plasterer bees were not responsible for the balding turf. They simply colonize areas where the turf is naturally thin. If you see swarms of small hairy or metallic colored bees constructing burrows or emerging from galleries in your garden or lawn, please resist the urge to treat them with insecticides. Several species of native pollinators, including anthophorid bees, yellow-faced bees, andrenid bees, halictid bees, as well as plasterer bees nest in the ground. Enjoy these beauties and give them a break. They pollinate plants and keep our planet humming.  

On a warm afternoon last week plasterer bees swarmed over the surface of a sun-drenched embankment along the Patuxent River. Excavations by hundreds of plasterer bees created tiny volcanoes of brick red soil along the slope. While some bees buzzed about, others were busy constructing burrows or dashing off to bring provisions back to their subterranean galleries.

Acknowledgements

Bug of the Week thanks native bee guru Sam Droege for helping to identify bees seen in this episode. We also thank Marlene for sharing an image of her bee-friendly yard, providing both a home for these fantastic native pollinators and the inspiration for this story. The wonderful article “Ecology, Behavior, Pheromones, Parasites and Management of the Sympatric Vernal Bees Colletes inaequalis, C. thoracicus and C. validus by S. W. T. Batra was used as a reference.